Fundamentals of HVOF Spray for Reconditioning Components {0599, 0679, 1000, 7000} Caterpillar

Caterpillar Products

All

Introduction

Table 1

Revision	Summary of Changes in SEBF9236
11	Updated table 2 and added a qualifying statement on clean dry air.
10	Put SEBF9233 back in Table 2. Revised Illustrations 47,48, and 49.
09	Removed SEBF9233 back in Table 2. Created Illustrations 5,20,22,23, and 24 Revised Illustrations 2 through 4, 6 through 19,21, and 25 through .46. Removed Group effectivity and replaced with Caterpillar Products All.
08	Added three serial number prefixes.

© 2019 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law.

Information contained in this document is considered Caterpillar: Confidential Yellow.

The purpose of this Guideline is to provide information on the basic process fundamentals of High Velocity Oxygen Fuel (HVOF) Spray for reconditioning components. Successful utilization of the HVOF spray process depends on incorporating other support types of equipment. All processing, equipment, and installation requirements must be understood for performance and safety reasons. Included in this document is information, including cost, on the required tools and equipment necessary to perform the described process.

For technical questions when using this document, work with your Dealer Technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

The manual either provides or references all the necessary information to achieve an understanding of the HVOF spray process.

Table 2

HVOF Spray Procedure Documents
Media Number	Publication Type and Title
SEBF2175	Reuse and Salvage Guidelines Thermal Spray Procedures for D3B - D6H TTT Pivot Shaft
SEBF8083	Reuse and Salvage Guidelines Inspection and Salvage of Rear Wheel Spindles for All Off-Highway Trucks
SEBF9233	Reuse and Salvage Guidelines HVOF Identification and Polishing (Superfinishing)
SEBF9273	Reuse and Salvage Guidelines Thermal Spray Procedures for D3 - D5G TTT Adjuster Yoke Shafts
SEBF9274	Reuse and Salvage Guidelines Thermal Spray Procedures for D7-D11 TTT Pivot Shafts
SEBF9276	Reuse and Salvage Guidelines Thermal Spray Procedures for Hydraulic Cylinder Rods
SEBF9277	Reuse and Salvage Guidelines Thermal Spray Procedures for 16M Tandem Housing
SEBF9284	Reuse and Salvage Guidelines Thermal Spray Procedures for Linkage Pins
SEBF9287	Reuse and Salvage Guidelines Thermal Spray Procedures for Motor Grader Blade Lift Yokes
SEBF9291	Reuse and Salvage Guidelines Thermal Spray Procedures for OHT Front Struts
SEBF9295	Reuse and Salvage Guidelines Thermal Spray Procedures for OHT Rear Struts
SEBF9297	Reuse and Salvage Guidelines Thermal Spray Procedures for TTT Bearing Sleeves
SEBF9298	Reuse and Salvage Guidelines Thermal Spray Procedures for TTT Dozer and Ripper Pins
SEBF9299	Reuse and Salvage Guidelines Thermal Spray Procedures for TTT Dozer Yokes
SEBF9304	Reuse and Salvage Guidelines Thermal Spray Procedures for WTS Pan Lift Yokes
SEBF9309	Reuse and Salvage Guidelines Inspection and Salvage of Front Wheel Spindles for Off-Highway Trucks
SEBF9340	Reuse and Salvage Guidelines Thermal Spray Procedures for MT Series OHT Front Spindle

For further information and background on the HVOF spray process or HVOF-related preparation and finishing processes, refer to the following publications or articles:

Table 3

HVOF Reference Publications
Reference Title	Publisher
"Thermal Spray Manual"	American Welding Society
"Thermal Spraying: Practices, Theory, and Application"	American Welding Society
"The Science and Engineering of Thermal Spray Coatings, Second Edition"	John Wiley & Sons, Ltd.
"Oerlikon Technical Review Magazine"	Oerlikon Metco

Safety

Illustration 1	g02139237

This bulletin is a reference to information provided in equipment operation manuals. Cat dealers are requested to read the safety sections of operation manuals cited in this bulletin.

Note: Refer to operation manuals for Oerlikon Metco equipment as the primary source of operating and safety information. Other references for operating and safety information are the following:

Table 4

Safety References
Publication Title	Publisher
"Flame Spray Handbook Vol. II - Powder Process"	Oerlikon Metco
"Welding Handbook, 8th ed., vol. 3"	American Welding Society (AWS)
"Thermal Spraying: Practices, Theory, Applications, and Safety."	American Welding Society (AWS)

Like any process that generates dust and fumes, the HVOF spray process involves a potential hazard to personnel. All personnel involved in this process must understand and become familiar with operating practices and regulations [Occupational Safety and Health Administration (OSHA) standards (US) or equivalent] for compliance.

Information in this bulletin is derived from the sources mentioned, but not all the safety points are covered here.

Environmental Health & Safety Advisory

High Velocity Oxygen Fuel (HVOF) Thermal Spray is a process that is an alternative to hard chrome electroplating on parts used in Caterpillar Products. Chrome electroplating uses the hexavalent form of Chromium, which is recognized by the international Agency for Research on Cancer (IARC) as a human carcinogen. Many countries have Occupational Exposure Limits (OEL'S) for Hexavalent Chromium, which ranges from 0.005 mg/m³ (3.12x 10^-10 lb/ft³) to 0.05 mg/m³ (3.12x 10^-9 lb/ft³) for an 8-hour Time Weighted Average (TWA) exposure. The electroplating process requires extensive EHS controls because of the hazards posed to employees and the environment by corrosive acid solutions of Hexavalent Chromium. The HVOF process is a dry process that eliminates the need for employee handling of corrosive chromic acid solutions. The HVOF process can be operated manually or robotically in a controlled booth environment. Although the HVOF process can facilitate compliance with OEL'S and comprehensive standards like the OSHA Hexavalent Chromium Standard, the HVOF process has inherent safety and health hazards, which must be addressed. The metal powders used for chrome coating can contain Chromium and other nickel. To protect employees and comply with OEL'S for Hexavalent Chromium and other materials, implementing the following actions is required:

Fire Prevention and Protection

Precautions for HVOF spray are essentially the same as for welding and cutting. Airborne metal dust, or finely divided solids, should be treated as a possible explosive and a breathing hazard. Adequate ventilation must be provided to minimize the danger of dust. Metal Powders used to deposit Chromium can also contain Nickel. The HVOF process will create dust particles, which can contain Nickel and some Hexavalent Chromium. Measure employee exposure time to document employee exposure to Hexavalent Chromium and Nickel.

U.S. Federal EPA emission standards require that exhaust systems for the HVOF spray industry have an efficiency of 99.99%. Federal, state, and local exhaust emission requirements in North America have become more demanding.

In the flame spray industry, the Dry Cartridge Dust Collection System is the most effective method for cleaning exhaust gasses.

Enclosed operations would also need local exhaust ventilation systems equipped with dust collectors. Employees performing dust collection system maintenance need to use respiratory protection, disposable coveralls, and protective gloves to minimize inhalation and skin exposure to Hexavalent Chromium and Nickel.

Good housekeeping must be practiced to avoid the accumulation of metal dust. Paper, wood, oily rags, and flammable solvents must be removed from the spraying area.

Safety Material

Compliance with OSHA Hazard Communication Standard requires current Material Safety Data Sheet (MSDS) and employee training.

Operating Considerations

HVOF differs from welding and cutting processes in sound generation. The high exhaust gas velocity generates noise levels of over 110 dB. Chronic exposure will likely result in hearing loss. A combination of booth sound insulation and personal equipment (earplugs and earmuffs) should be used, to reduce this noise to a safe working level.

Like welding, the HVOF process involves gas cylinders or bulk gas containers. Improper storage, handling, and/or use of gas cylinders can create serious safety hazards. For example, if a valve is broken off a full gas container during a fall, the container will become a missile. If an oil-contaminated regulator or gauge is installed in an oxygen system, the assembly will explode.

For further detail on these operating hazards, refer to the following:

Table 5

Operating Considerations References
Publication Title	Publisher
"Safety in Welding, Cutting, and Allied Processes" ANSI/ASC Code Z49	American National Standards Institute and American Welding Society

HVOF Spray Equipment

Maintain and operate HVOF spray equipment exclusively to standards set by the equipment manufacturer. All operators must be instructed to become familiar with the operation of the spray equipment. If an HVOF spray gun malfunctions or backfires, the cause of the trouble must be investigated.

When HVOF spraying is completed, the system must be properly "shutdown" as follows:

1. Close all gas cylinder valves.

2. Open the gun valves to release hose gases, with room ventilation on.

3. Back out all regulator screws until free.

4. Close the gun valve.

5. Check all first stage regulators to ensure that no pressure buildup is taking place. Pressure buildup would indicate that a bottle valve has not been tightly closed.

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Never use an open flame to light the thermal spray gun. Serious burns or other personal injury could result. Equip the gun with an electric ignition system or use a spark lighter.

Abrasive Blasting Equipment

Maintain blasting equipment according to the manufacturer specifications. Replace worn parts for efficient operation. Replace deteriorated hoses and nozzles.

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Grit blasting produces airborne particulates that can act as respiratory irritants. If inhaled, these particulates can cause serious injury or death. Additionally, the grit from this process can be abrasive to the skin and eyes of the operator and can cause serious injury. If grit blasting is performed manually or outside of a grit blast cabinet, operators must be provided with respiratory protection, face shields, and helmets. Information on face shields and helmets can be found in ANSI/ISEA Z87.1 (American National Standard for Occupational and Educational Eye and Face Protection Devices) and ANSI/ISEA Z89.1 (American National Standard for Industrial Head Protection). Information on the selection, operation, and maintenance of a respiratory device can be found in ANSI/AIHA Z88.2 (Practices for Respiratory Protection) or other local approval authority documentation.

Mechanical Stripping and Finishing Equipment

Maintain lathes, grinding, and finishing equipment according to the manufacturer specifications. Replace worn parts for efficient operation. All operators must be instructed to become familiar with the lathe and grinding equipment operations.

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Serious injury or death can result from contact with rotating parts or pinch points. To avoid injury, rotating parts, such as grinders, superfinishers, and lathes, should only be operated if all guards and protective devices are properly installed and in good working order. All equipment should be operated according to the manufacturer instructions.

Other Safety Hazards

Other safety hazards include compressed gases, thermal burns, high voltage, and mechanical pinch points from robots and turntables, which are potential ergonomic hazards involved with handling parts. The American Society of Metals Thermal Spray Society (TSS) has made two Safety Guidelines available to help provide control of the process: "SG001-02 Safety Guidelines for the Handling and Use of Gases in Thermal Spraying", and, "SG003-03 Thermal Spray Booth Design Guidelines". The guidelines are available free from TSS web site or Corporate EHS.

Process Fundamentals

High Velocity Oxygen-Fuel (HVOF) spraying is a process where fine metallic materials are deposited onto a prepared surface. HVOF is considered a "warm" part salvaging method when compared to flame spray "cold" or welding and brazing (both "hot" processes). HVOF is considered a warm process because the surface temperature of the part is kept below 205° C (400° F) when a coating is applied. Therefore, the part experiences no metallurgical or physical changes.

The Caterpillar HVOF spray salvage process uses an oxygen-fuel mixture. The Diamond Jet Hybrid Spray System by Oerlikon Metco utilizes either propylene, propane or natural gas as a fuel. The fuel gases are mixed in a nozzle system in the front portion of the spray gun. The mixed gases are ejected from the nozzle of the gun and ignited externally. The ignited gases form a circular flame, which surrounds the powdered spray material as the material flows through the gun.

The circular flame shapes the powder stream to provide uniform heating and acceleration of the spray material. Combustion temperatures approach 2760° C (5000° F)

Pre-selected oxygen, fuel, and airflow values optimize the dwell time of the spray material in the flame.

Caterpillar salvage applications and process orientation in this guide assume the use of a Diamond Jet Hybrid Spray System by Oerlikon Metco.

The gas exhaust velocities of the Diamond Jet Hybrid Spray System approach 2134 m/s (7000 ft/s) [3 to 4 times the speed of sound]. Elevated particle velocities, optimized powder feed rates, and internal central powder injection impart both thermal and kinetic energy to the powder particles. The high velocity particles flatten when impacting on the substrate to form dense tightly bonded coatings.

Nitrogen is used as a carrier gas for feeding the spray materials through the system. The Diamond Jet Hybrid Spray System uses 9.5 L/min (2.5 US gal/min) of water to cool the nozzle of the gun.

Powder Feed

All Diamond Jet Hybrid Spray Systems are fed by a pressurized feeding system. The powder is transported and delivered to the gun by an inert gas (pre-purified Nitrogen) at a constant rate, independent of the spray gun orientation or movement. The feed unit provides a real-time powder feed rate, to help with coating process control.

Illustration 2	g06387461
Typical example of a cross sectional view of the Hybrid Nozzle Diamond Jet Spray System Gun. (A) Powder (B) Oxygen (C) Fuel (D) Air (E) Water In (F) Water Out (G) Distribution Plug (H) Nozzle (J) Nozzle Nut (K) Air Cap Body (L) Water Adaptor (M) Baffle (N) Nut (O) Air Cap

Coating Fundamentals

Through the High Velocity Oxygen Fuel (HVOF) spray process, a fine metallic uniformly heated material is deposited onto a prepared surface. When the particles strike a surface, the particles flatten (elongate), rapidly cool and quench to form micro-thin platelets. The platelets conform to the surface of the substrate and to each other. The bond between the base material and the HVOF coating is mechanical.

As the sprayed particles continue to impinge onto the surface, a layer or lamella structure is formed. The lamella structure of HVOF coatings is dense and uniform. HVOF coatings have the following characteristics:

• High density

• High bond strength [more than 83 MPa (12,000 psi)]

• Essentially stress free

• Low porosity (less than 3%)

• Fine as-sprayed finishes

• Greater hardness (DPH₃₀₀ 1000-3000)

• Metal working capabilities

• Excellent wear and corrosion resistance

• Greater thickness

Since multiple particles are needed to create a coating, several transverse passes of the gun are required to produce the desired coating thickness. These multiple passes should be performed at a constant rate by mechanical manipulation. The actual thickness of a coating depends on the run out of the component being salvaged plus an allowance for finishing. The finishing allowance is generally 0.05 - 0.08 mm (0.002 - 0.003 inch) on a side.

The formed coating is used for "surface" type applications. The coating will not provide any strength to a part. The coatings only function is to add some desirable characteristic to the surface that is lacking in the work piece part. Desirable HVOF spray characteristics include:

• Corrosion protection

• Better wear characteristics

• Dimension restoration

• Electrically conductive or resistive

Because of the nature and structure of HVOF spray coatings, HVOF should not be used when the coatings will be subjected to line or point-to-point contact and severe, sharp, and repeated type of impact.

Chrome Stripping Mechanically

The chrome on a component being salvaged can be removed mechanically or chemically. All plating shops that rechrome components remove existing coatings chemically.

A solution containing chrome as a liquid is considered a hazardous waste, which makes disposal expensive. Plating companies are prepared to handle these dangerous chemicals, and are familiar with waste disposal methods and costs.

Note: A plating shop can be held financially responsible for problems caused by the company who handles the waste disposal.

To avoid these hazardous chemicals, the hazardous waste, and waste removal costs, the Caterpillar HVOF spray salvage program requires chrome to be removed mechanically. Mechanical chrome removal methods are:

• Conventional (wheel) Grinding

• Belt Grinding

• Turning

• Grit Blasting

The most economical method to remove chrome mechanically is belt grinding. Belt grinding removes chrome twice as fast as wheel grinding, and requires a much lower capital investment than conventional grinding.

Illustration 3	g06389431
Chrome stripping

Belt grinding can be accomplished on most good quality lathes, by simply attaching a belt grinding machine to the cross slide. The in-feed adjustment will control the amount of load on the component and grinding belt. The cross slide feed will control the feed rate of the belt grinder along the component. One can convert some wheel grinders to belt grinders, by substituting a contact wheel for the stone wheel and installing a belt idler assembly.

Chrome removal can be performed at a rate of 0.025-0.038 mm (0.0010-0.0015 in) per pass at a traverse rate of 6 mm (0.25 inch) per revolution with the proper set-up and tooling. A pass is defined as the belt grinder making a trip in one direction the length of the component. 3M 966F belts should be used for chrome stripping.

If necessary to remove an HVOF coating from a piece, use a 3M Trizactgrit 70 micron diamond belt, but only until breakthrough of the steel substrate. Test and development of belts for chrome stripping continues, as does evaluation of different stripping methods.

A copper-sulfate/water solution can be prepared and atomized onto the dried surface of the component after stripping passes, to determine the extent of chrome removal. This procedure is not always necessary, because on most components a color change can be noticed when the base material is exposed. Rewash to remove the solution prior to grit blasting.

Coolant is necessary for chrome stripping and should be flooded into the contact area between the belt and component. As contact pressures increase, the pressure of the coolant must be adequate to assure that the belt and component are being cooled properly. An additive must be mixed with coolant water to prevent rust, and counteract bacteria growth. Treatment of hard make up water may be necessary, since the minerals can inhibit additive performance.

Examples of additives are listed in "Surface Finishing".

Coolant filtering is necessary to remove grinding "mud" if the machine is also used to finish HVOF sprayed components. Small abrasive particles in the coolant can cause problems with surface finish. A filter fixture/pump setup that uses a paper roll element has several advantages, including significant capacity, automatic advancement of the filter roll, and the ability to handle several machines simultaneously. The filter element should be at least 50% efficient for 10-micron particles.

Check with your local environmental authorities on the handling of waste coolant and filter elements containing chrome particles. Once the water evaporates, the chrome may be sold as a waste metal, similar to the blow-by HVOF powder.

Surface Finishing

HVOF coatings can be finished by the following mechanical methods:

• Conventional (wheel) Grinding

• Belt Grinding

The most economical method to finish an HVOF coating is belt grinding. Belt grinding is sometimes referred to as belt sanding with a diamond belt or other aggressive abrasive material. Belt grinding will finish HVOF coated components twice as fast as wheel grinding.

Belt finishing of most components will require a two-step process. The first step will be to grind the HVOF coating with a 3M Trizact M70 diamond belt to remove most excess material and any taper from the component. The second step is to use the super finisher to grind the component to the proper size and surface finish.

Although possible to finish components to the specified size and surface finish using only a grinder, a super finisher has three important purposes. This procedure will remove any blemishes or "striping" (barber poling) the belt grinder leaves on the component, thereby eliminating variations in finish due to lathe conditions and operator experience. Second, this procedure creates a slight crosshatch in the coating similar to the fine cracks which occur in plated surfaces. This finish is desirable to help lubricate seals and enhance seal life. The third purpose is to achieve a more polished surface appearance, which is similar to what is produced by plating. A 20 micron film should be used for superfinishing.

Belt grinding can be accomplished on most good quality lathes, by mounting a belt grinding machine to the cross slide. The in-feed adjustment will control the amount of load on the component and grinding belt. The cross slide feed will control the feed rate of the belt grinder along the component. It is possible to purchase wheel grinders converted to belt grinders.

Illustration 4	g06389441
Abbott CNC Roll Grinder with Belt Grinding Attachment

The super finisher should be mounted to the cross slide of a lathe. To save floor space and reduce capital investment, the super finisher can be combined up with a rear-mount belt grinder in a set on one lathe. This arrangement up will allow both operations to be performed on the same machine, avoiding excess material handling.

With the proper set-up and tooling, HVOF coatings can be ground at a rate of 0.038-0.051 mm (0.0015-0.0020 inch) per pass at a traverse rate of 5.0 mm (0.1875 inch) per revolution. A pass is defined as the belt grinder making a trip one direction the length of the component. HVOF coatings can be super finished at a rate of 0.013-0.038 mm (.0005-.0015") per pass at a traverse rate of 0.64 m/min (25 in/min)

Coolant with a rust and bacteria inhibitor is required for the HVOF grinding and super finishing operations. Hard water may require treatment, since minerals can interfere with rust inhibitors and other coolant additives. The coolant should be flooded into the contact area between the abrasive and the component. As contact pressures increase, the pressure of the coolant should be enough to assure that the abrasive and components are being cooled properly. To improve diamond belt life, a coolant formulated for machining high Nickel content materials should be used. The following coolants meet this requirement:

• Castrol WE3-046A

• Castrol Syntello 9954

• CimPerial 1070 from Cincinnati Milacron

• Bosse Grind, Rust Bar 750 (Star Metal Fluids)

• Milacron 46C

Since lathe coolant systems are only designed to let coarse chips collect in the sump, the system must be modified to provide adequate filtration. The lathe pump should pipe the coolant to an auxiliary filtering system which is at least 50% efficient for 10 micron particles. This is necessary to remove abrasive "mud" which can damage rod finish and also the lathe. The modification should also include coolant plumbing to wash abrasive material from the machine ways, to prevent premature wear. A filter tank/pump setup using an automatically advancing paper roll element has several advantages. These systems have far more capacity than canister filters, and can be sized to handle several machines simultaneously. Filter fixture suppliers include:

• Oberlin Filter Company

• Hydromation Division, Filtra Systems

• J.R. Schneider Co., Inc.

• Hoffman Air and Filtration Systems

Illustration 5	g06387613

Filter paper suppliers include:

• Lydall Manning

• National Filter Media Corp.

• Industrial Filter Fabrics

The products and manufacturers listed here are not intended as the only acceptable choices. For information on these or other suppliers, questions, or to address an urgent issue, use the following resources to communicate your request to Caterpillar Repair Process Engineering: Cat dealer Technical Communicator, Dealer Solution Network (DSN), Caterpillar Technical Representative, or Knowledge Network.

Check with your local environmental authorities on the handling of waste coolant and filter material.

Once the water has been removed by evaporation, the waste material may be sold as a waste metal similar to the blow-by HVOF powder.

If necessary to remove all of an HVOF coating from a piece, the diamond belt should only be used until first breakthrough of the steel substrate.

Support Equipment and Operations

Straightening

A component with more than 0.076 mm (0.0015 inch) runout will have to be straightened before the HVOF salvage process.

The component should be loaded into a straightening press with adequate gauging to straighten the component to less than 0.038 mm (0.0015 inch) runout per every 914 mm (36 inch).

Straightening is crucial to conserving spray materials, and in minimizing both thermal spray and machining cycle times.

Reducing overall component runout, decreases the volume of spray material that must be deposited onto the component to compensate for the out-of-round condition. Components requiring higher volumes of material will increase the thermal spray cycle time. Component machining times will also increase, because of the need to remove the excess spray material.

Degreasing

All components should be degreased before the grit blast operation. Degreasing helps prevent contamination of the grit, and assures there is no oil or grease on the surface of the component to be coated. Oil and/or grease on the surface of the component will increase the probability of finishing problems and coating defects.

Grit Blasting

Grit blasting before the thermal spray process is considered surface texturing. This operation provides a slightly rough surface texture that the HVOF metal particles will interlock with. Clean, dry compressed air, and sharp, coarse blasting abrasive that is free from contaminants must be used to avoid finishing problems.

Two types of grit blasting systems are found in most shops: pressure and suction. For surface preparation of a coating, the pressure type system is preferred because:

1. Pressure blast systems can handle both aluminum oxide and steel angular grits.

2. A pressure blast system is more efficient and, therefore, more economical.

3. Pressure blast provides the best surface texture and depth using either aluminum oxide or angular steel grit.

4. A suction head can be mounted next to the pressure blast nozzle, to quicklyand efficiently remove blast media as the surface texturing is being completed.

Aluminum oxide 20 mesh is the recommended grit blast media to prepare surfaces for HVOF.

Aluminum oxide is a hard and brittle abrasive, used primarily on heat-treated steel substrates. It is not used for preparing aluminum or cast type substrates because the fine dust generated during the blasting operation tends to embed into the surface of the component. Because this type of grit is light in weight, it can be used at low pressures. The use of lower operating pressures allows the use of aluminum oxide grit on hard and soft components. The recommended blast air pressure is 413 kPa (60 psi). Heat-treated rods should be rotated at 61 SMPM (200 SFPM). Non-heat treated rods should be rotated at 122 SMPM (400 SFPM), with the blast nozzle traversing across the piece at a rate of 5.0 mm (0.1969 inch) per revolution. Blast nozzle to work piece distance should be maintained at a 101 mm to 127 mm (4 inch to 5 inch) range to obtain a minimum surface profile of 6.0 µm (250 µinch).

Using higher than recommended pressures results in rapid breakdown of grit, and more grit usage.

It may be necessary to grit blast chrome from long, small diameter parts due to bending problems when grinding. This method shall be used when necessary, since the chrome particles will mix with the grit. Chrome or other grit contaminants can be embedded in the surface of the component during blasting.

Note: Visually inspect used grit to ensure sharpness. If dull or contaminated grit is found, replace the grit before poor surface preparation results.

Masking Aids

Masking is required to protect critical surfaces and holes from the effects of the grit blasting and thermal spraying. Any type of material that can withstand the effects of either operation is considered a suitable masking material.

The mask can be permanent sheet metal or a temporary material. Temporary-type masking materials are:

• Hard Rubber

• High temperature silicon rubber

• high temperature fiber type materials

• Several layers of duct or masking tape

• Cloths

• Liquids

Spray Booths and Rooms

Any flame spraying process generates dust and fumes. The HVOF process also generates an extreme amount of noise, due to gas exhaust velocities of 7000 ft/sec (2134 m/sec). The noise will be in the 135 dB to 140 dB range.

For environmental control and personnel safety, an enclosed soundproof area is appropriate. Dealer Support or a local supplier can recommend various dry cartridge exhaust and soundproof rooms, to meet your local safety standards and regulations.

Rotational/Traverse Equipment

Rotating the cylindrical components should be accomplished in a lathe or other dedicated rotational device. The standard lathe or dedicated rotational device should provide variable rotational settings to relatively high RPM capability. Specially designed rotating systems manufactured by Oerlikon Metco and other companies can withstand the dusty spray environment, yet provide the part rotational requirements.

Rotational requirements for parts are provided in the Applications section. The following formulas can be used to calculate either RPM (revolutions per minute) or SFPM (surface feet per minute) for a part.

(3.82 x SFPM)/ rod diameter in inches = RPM

0.262 x RPM x rod diameter in inches = SFPM

For traverse motion of the HVOF spray gun, the following guidelines should be used to apply an even coating deposit:

• Flat work (non-rotating): Traverse at a rate of 15-30 cm (0.5-1.0 inch) per second, making 6.3 mm (0.25 inch) gun increments per pass.

• Round/Rotating Work: Traverse the gun at a 5.0 mm (0.1875 inch) per revolution.

Painting

After a hydraulic cylinder rod has been repaired, the eye, yoke, or other method of attachment should be repainted to prevent exposure of unprotected surfaces.

During testing, the highest level of corrosion occurred on the blend radius shown in illustration 6. A recommended practice to help avoid corrosion in this area is to paint the area when the repair has been completed.

Note: Protect the pin bore, pin bore face, and all threaded holes during the painting process.

Illustration 6	g06389461

Improving Efficiencies

Improving the efficiency of any HVOF salvage operation is an on-going continuous task. The following ideas are recommendations from Dealer Support, other Cat dealers, suppliers, and Caterpillar Technical Center.

These ideas or examples should be used as starting points to generate good efficiency improvements at your facility.

The following topics will be discussed:

• Color Coding

• Batch Processing

• Equipment Usage

• Blast Cabinets

• Coating Repairs

Color Coding

Color coding of components as they are initially inspected is a good way to initially separate in-process inventory. A spot of paint on the chrome area of a rod can identify a rod for eye repair, straightening, HVOF repair or rerodding.

Color coding is also a quick way to determine the amount of in process inventory in the Hydraulic Repair Area.

Batch Processing

Rods of similar diameter or length can be processed together to minimize machine set-up times.

Wheeled "A" frame carts can be used to move batch parts quickly from one operation to the next.

A few HVOF coated rods of high volume can be kept on hand to improve turn around time. A large inventory of HVOF coated rods is not recommended, unless warranted by sales volumes.

Equipment Usage

Initially four lathes, four headstock/ tailstock configurations, or a combination of the two should be purchased to perform the HVOF process. These pieces of equipment should have similar capacities, so that the same size component can be processed in each area. Itis recommended to usethe equipment as rotational devices for the following operations:

• Chrome Stripping

• Surface Preparation (grit blast)

• HVOF process

• Coating Finishing

The volume of components that must be processed to justify the capitol expenditure of this magnitude requires the sufficient volume. Performing a market study will determine volume of Caterpillar and non-Cat opportunity.

A fifth smaller lathe or headstock/ tailstock configuration can be used for stripping chrome and coating finishing of small diameter components.

The following stripping and finishing equipment configurations are recommended:

Four-Lathe Shop

• Chrome Stripping Kelsey Super G-4 Belt Grinding Machine

• Coating Finishing Kelsey Super G-4 Belt Grinding Machine Kelsey SF-4 Super Finishing Machine

Five-Lathe Shop

• Chrome Stripping Kelsey Super G-4 Belt Grinding Machine

• Coating Finishing Kelsey Super G-4 Belt Grinding Machine Kelsey SF-8 Super Finishing Machine

• Small Lathe Kelsey Super G-1 Belt Finishing Machine Kelsey SF-4 Super Finishing Machine

The grinder on the Coating Finishing machine should be used for one or two passes to rough finish the HVOF coating. The Super Finisher will then be used to polish the component into the proper tolerances (dimensionally and surface finish) in one to two passes.

Blast Cabinets

Grit blasting and HVOF coating on the same piece of equipment is not recommended.

The throughput time of the HVOF salvage operation will be drastically reduced by performing these two operations on the same piece of equipment.

A combination cabinet will become contaminated with the blasting media. Contamination will reduce the cleanliness level of the components being coated, thus reducing the bond strength of the HVOF coating.

Coating Repairs

The following guidelines should be used when repairing a blemish on an HVOF coated component:

1. If the coating thickness is less than 0.51 mm (0.020 inch), the coating should be completely removed and returned to the surface texturing operation.

2. If the coating thickness is over 0.51 mm (0.020 inch), then the following steps should be followed:

   1. Remove 0.13 mm (0.005 inch) of coating thickness.

   2. Heat the component to 177° C (350° F) for 3 hours to remove all oils from the surface of the coating.

   3. Apply a degreasing agent to the surface of the coating and dry with clean shop air.

   4. Apply the HVOF Coating.

Surface Finish Inspection

When an HVOF coated component has not failed at time of disassembly, the surface roughness of the component must be measured. If the surface finish does not meet the specification, the component should be repolished and checked again. After repolishing, the following inspection procedure should be conducted:

• Place component on rollers, in a lathe, or hang vertically.

• Clean the inspection area with isopropyl alcohol and a lint free cloth.

• Holding an LED pen light less than 1 ft from the surface and at an approximately 30 degree angle, look for any shiny sparkles. If any are seen, circle the area with a permanent marker or paint pen.

• Hold a ball point pen at approximately a 45° angle and lightly drag the tip across the marked areas. Reject the part if a pit is felt when moving the pen across the surface.

Illustration 7	g06038724
Holding the LED pen light less than 1 ft from the surface and at an approximately 30° angle.

Illustration 8	g06038694
Holding the ball point pen at approximately a 45° angle.

HVOF Spray Equipment

Illustration 9	g06389462

Illustration 10	g06389769

The Caterpillar HVOF spray salvage program will use the Diamond Jet Hybrid Spray System byOerlikon Metco. The Diamond Jet Hybrid Spray System consists of the following basic components:

• Hybrid Diamond Jet Gun (DJ-A Automatic)

• DJC Diamond Jet Control Unit

• 9MPDJ or DJP Powder Feed Unit

• 2DJR Diamond Jet Gas Regulators and Manifolds

• 4AC Air Cleaner

• 7GNR Nitrogen Regulator

• DJC 2600 Water Sensing Interface Box

• DJ 2700 Hybrid Air Cap Assembly (designed for propylene, propane, or natural gas as a fuel)

Note: Hydrogen assist is required when using propane, propylene, and natural gas.

Note: The TAFA JP5000 is an option for the Diamond Jet Hybrid Spray System.

Illustration 11	g06389879
9MP-DJ Powder Feed Unit on right DJC Diamond Jet Control Unit on left

Illustration 12	g06389890
Vertical Spray Cabinet

Illustration 13	g06389915
DJ2700 Hybrid Gun Arrangement

Sound Suppression Equipment

The acoustical spray room should meet the following minimum parameters:

• Walls and roof shall have a minimum Sound Transmission Class (STC) rating of 40 as tested in accordance with ASTM E90-75 and noise Reduction Coefficient (NRC) of 0.95 tested in accordance with ASTM C423-77. See table below.

• Windows should be provided with a number six filter to prevent glare when viewing the thermal spray process in operation. Windows should also be thermopane glazed and supplied with a desiccant material between the panes to prevent fogging.

Table 6

Acoustic Performance Sound Transmission Loss dB E-90-75
Octave Band Center Frequency (Hz)	63	125	250	500	1k	2k	4k	8k	STC
Noise Shield Regulate	20	21	27	38	48	52	56	—	40
Noise Lock Door	—	26	42	43	47	61	61	67	47
Noise Lock Windows	27	28	31	47	55	61	61	67	47
Sound Absorption Coefficients(1)
Noise Shield Regulator	—	0.89	1.20	1.16	1.09	1.01	1.03	0.93	0.95
Noise Reduction	—	15	19	24	34	41	46	45	50

(1)	ASTM C423-81A Standard test method for sound absorption and absorption coefficient via reverberation method, mounting method A, formally mounting number four.

Consult your local environmental laws for exact sound regulations.

Illustration 14	g06389970
Blast Cabinet (right) and HVOF Cabinet (left).

System Recommendations

Powder Delivery

Different powder feeder hoses are available from Oerlikon Metco that have varying internal diameters. The different sizes are coded by color, as shown in the table below. Cat dealers generally use the blue powder feed hose, however, the appropriate choice of hose depends the length of the hose. Each operation should consult with an Oerlikon Metco representative to determine the appropriate internal diameter for the powder feed hose.

Table 7

Oerlikon Metco's Standard Powder Feed Hose Sizes
Hose Type	Insides Diameter
Blue	Ø 2.29 mm (0.090 inch)
Orange	Ø 3.18 mm (0.125 inch)
Black	Ø 4.76 mm (0.188 inch)

Fuel Delivery

Bulk fuel storage tanks must be heated to prevent fuel gases from liquefying. Also, an important procedure is to have gas lines from the bulk storage tanks to the Oerlikon Metco equipment heated to prevent gas condensation.

Spray booths or shop areas that are not climate controlled should heat the fuel gas lines from the Oerlikon Metco controller to the HVOF gun to prevent condensation.

Illustration 15	g06389978
Bulk Oxygen Tank

Illustration 16	g06389982
Natural Gas Arrangement

Illustration 17	g06385002
HVOF Shop Air Schematic (1) Upstream Filter (2) Air Dryer (3) Downstream Filter (4) Downstream Filter

Dry, clean shop air is critical to the quality of a thermally sprayed coating. Separate air filters and an air dryer should be used prior to the shop air entering the HVOF system.

Show/hide table

NOTICE
Clean dry air is defined as ISO 8573 - Class 3 air or better.

The preferred system configuration is shown in the HVOF Shop Air Schematic. refer to Illustration 17. The air dryer [2] should have a filter [1] placed up stream and two filters [3, 4] down stream. Refer to Illustration 17.

1. Particulate Filter (5 micron) - Wilkerson: FC35-OC-F00 or equivalent

2. Air Dryer - Pneumatech AD-1500, AD-1700 or equivalent (based on air consumption and the ambient climate in the shop)

3. Coalescing Filter (0.5 micron) - Wilkerson: M35-OC-FS0 or equivalent

4. Coalescing Filter (0.01 micron) - Wilkerson: M35-OC-F00 or equivalent

Water Chiller

A water chiller for the 2700 Hybrid water-cooled nozzle by Oerlikon Metco must meet the following parameters:

Table 8

Water Chiller Parameters
Water	Parameter
Flow	7.6 L/min (2.0 US gal/min)
Temperature (Inlet to Gun)	Below 26.6° C (80° F)
Pressure	275.6 kPa (40 psi)
Cooling	30,000 BTU/hour (31,650 kJ/hour)
Cleanliness	Tap water

Tap water can be used to cool the nozzle in most locations and then diverted to drain. If water recycling is required, the following chiller or equivalent is recommended:

• 5MK Heat Exchanger by Oerlikon Metco

Exhaust/Ventilation

For environmental control and personnel safety, a proper dust and fume exhaust system is required. EPA (U.S.) rules dictate exhaust systems be 99.9% efficient. Both Torit and Oerlikon Metco can supply the required equipment.

Illustration 18	g06389991
Exhaust System for grit blast and HVOF.

Illustration 19	g06389993
CNC Panel to control grit blast and HVOF

Manipulators/CNC

The HVOF/Grit Blast cells are computer controlled to provide high-quality coatings via a controlled process. Vertical or horizontal booths can be used to blast and spray the cylinder rods.

Illustration 20	g06387621
HVOF Coating being applied to a hoist cylinder

Illustration 21	g06389994
HVOF Spraying Operation

Design/Support

Cat dealer Support and Research can provide the necessary information for planning an installation. Working with suppliers, a turnkey package can be created to fit the requirements of the dealer.

Progressive Surface Design

Illustration 22	g06386528
HVOF Facility (1:60 Scale) (D) Dust Collector and Blower (To be Located Outside) (E) Heat Exchanger (Optional) (F) Powder Feeder (Optional) (G) JP-800 Controller (Optional) (H) Electrical Enclosure (J) Booth Walls Are Shown Transparent

Table 9

HVOF Facility Dimensions
Location	Minimum	Maximum
A	5968.2 (234.97)	5974.8 mm (235.23 inch)
B	14141 (556.74)	14148 (557)
C	5485.6 mm (215.97 inch)	5492.2 mm (216.23 inch)

Illustration 23	g06386694
Grit Blast Facility (1:60 Scale) (N) Electrical Enclosure (P) Dust Collector and Blower (To be located outside) (R) Sweco (S) Pressure Pot System (T) Booth Walls Are Shown Transparent

Table 10

Grit Blast Facility Dimensions
Location	Minimum	Maximum
K	4095.8 mm (161.25 inch)	4102.4 mm (161.51 inch)
L	12552.2 mm (494.18 inch)	12558.8 inch (494.44 mm)
M	5502.4 mm (216.63 inch)	5509 mm (216.89 inch)

Ring Power System

Illustration 24	g02759121
Fintech Grit Blaster

Illustration 25	g06389052
Fintech Grinder

Illustration 26	g06390187
Zoom of Fintech Grinder

Illustration 27	g06390207
HVOF Machine

Illustration 28	g06390220
HVOF Spray Nozzle

Illustration 29	g06390236
Stainless Steel Cover

Illustration 30	g06390245
Infrared Heat Sensor

Illustration 31	g06390250
Zoom of HVOF Control Panel

Illustration 32	g06390254
HVOF Coated Cylinder and Equipment

HVOF Machining Equipment

Illustration 33	g06390262
Belt Grinding Machine

Cat dealer HVOF salvage program applications will use a mechanical method to strip existing chrome or HVOF coating from salvageable hydraulic cylinder rods and OHT struts. A mechanical method will also be used to finish all components after the HVOF operation. The choices of grinding/finishing equipment are:

• Abbott CNC Cylindrical Grinder

• Finishers Tech Super G-6 Belt Grinding Machine or equivalent

• Supfina 210, IMPCO, GEM, or equivalent

Illustration 34	g06390318

Equipment Specifications

Chrome Stripping and HVOF Grinding:

• Finishers Tech Super G-6 Belt Grinding Machine ( 51 mm (2 inch) wide contact wheel) or equivalent [Two required, one for chrome stripping and one for HVOF finishing]

• Variable Speed Controller

• 14.9 kW (20 hp) motor

• Digital Amp load readout

• Capable of 3048 surface meters per minute (10,000 SFPM) belt speed

• 50 mm (2 inch) diameter air cylinder for belt tension

• 90 Durometer Shore A, Plain face contact wheel (finishing)

• 90 Durometer Shore A, Scoop (or J-72) wheel (stripping)

The contact wheel diameter depends on the lathe the machine is mounted on. A large wheel will provide more clearance between the grinder and tailstock. Most installations use a 406 mm (16 inch) diameter wheel.

Scoop wheels, which have slanted slots cut into the wheel face, are used for stripping because they exert more unit pressure on the cylinder rod or strut. An alternate to the Scoop wheel is the J-72. This is similar in appearance to the Scoop wheel, except the slots are flat-bottomed and do not break out the sides of the face.

The inside diameter of some as-delivered contact wheels has been found to be rough and/or not concentric with the tire. It is recommended that you use a drawing from Dealer Support to produce hubs for Ø 406.4 mm (16.00 inch) diameter wheels, and bore the wheels to fit the hub. The wheels and hubs should be balanced individually at speeds up to 1,500 RPM, for interchangeability. Whenever switching to a different wheel on a hub, the replacement wheel should be dressed for concentricity before a belt is installed. Use the following procedure:

1. The grinder should be mounted on the machine with the wheel shaft centerline as parallel as possible to the machine centers.

2. Use chalk, or preferably a white paint stick, to place marks the full circumference of the contact wheel.

3. Place a straight rod between machine centers, and use solvent to clean a section of the rod.

4. Cut a rectangular section of adhesive backed abrasive that is wider than the contact wheel, and apply the abrasive section lengthwise on the clean surface.

5. Rotate the rod and position the contact wheel so the wheel is about 6.35 mm (0.250 inch) from the abrasive surface.

6. Start the grinder and set the speed to 304.8 surface meter per minute (1,000 SFPM) or less (240 RPM with a Ø 406.4 mm (16.00 inch) diameter wheel).

7. Infeed slowly until the wheel contacts the abrasive, then traverse the wheel across the abrasive.

8. Infeed an extra 12.70 µm (500 µinch) and repeat the traverse, until the entire face of the contact wheel has been dressed.

Illustration 35	g06389081
Finishing a rod with a diamond belt

Illustration 36	g06390364
SG-6 control panel

Illustration 37	g02778421
Hub, with wheel clamp ring loose

Illustration 38	g06390505
Scoop wheel - Ø 406.4 mm (16.00 inch) diameter, 51 mm (2 inch) wide.

HVOF Finishing

• Supfina 210, IMPCO, GEM, or equivalent

Illustration 39	g06391028
Supfina 210 Super Finisher

Illustration 40	g06391042
Finisher's Tech SF- 4 Super Finisher

HVOF Machining Abrasives

Cat dealer HVOF spray salvage program applications will use the following abrasives to strip existing chrome plating, or HVOF coating, from salvageable hydraulic cylinder rods and OHT struts, and to finish all components following the HVOF operation.

Chrome Stripping

3M Cubitron 966F 24 grit

51 mm x 3353 mm (2 inch x 132 inch) belts will be required for the Finishers Tech Super G-6 Belt Grinding Machine. If necessary, 51 mm x 1524 mm (2 inch x 60 inch) belts for the optional grinding equipment (Finishers Tech Super G-1 Finishing Machine).

Show/hide table

NOTICE
This operation should always be performed wet.

The product is designed for wet grinding where high, sustained stock removal is required. The belt will perform well in moderate pressure grinding on various materials including steel, stainless steel, and exotic alloys. The recommended belt speed is 6000-7000 RPM.

When using the 967F Multicut belt to remove chrome, a high amp load (that is, 10 amps or greater above the idle amp load) should be used to break down the special ceramic aluminum oxide mineral. By continuously breaking down the mineral on the belt, new cutting edges are exposed.

HVOF Stripping

3M Trizact Diamond Cloth belts 663FC (70 micron)

51 mm x 3353 mm (2 inch x 132 inch) belts will be required for the Finishers Tech Super G-6 Belt Grinding Machine.

HVOF Finishing (Grinding)

3MTrizact Diamond Cloth belts 663FC (70 Micron)

51 mm x 3353 mm (2 inch x 132 inch) belts will be required for the Finishers Tech Super G-6 Belt Grinding Machine. 51 mm x 1524 mm (2 inch x 60 inch) belts for the optional grinding equipment (Finishers Tech Super G-1 Finishing Machine).

Super Finishing

3M Diamond Microfinishing film 675L (20 micron)

Illustration 41	g06391050
Finishing with diamond belt

Illustration 42	g06389076

102 mm (4 inch) wide 3M diamond strips will be required for the Finishers Tech SF-4 Super Finishing Machine. 203 mm (8 inch) wide 3M diamond strips will be required for the optional equipment (Finishers Tech SF-8 Super Finisher Machine). The 3M strips can be ordered in various lengths. 1219 mm (48 inch) of cutting surface with a 610 mm (24 inch) leader and 610 mm (24 inch) tail is a standard length. The leader and tail portion is required to feed the strips through the super finisher.

A good practice is to keep a few of the plastic spools the 3M strips are shipped on, to reduce the machine setup time when switching 3M strip grades.

Belt Storage

When belts are not in use, they should be hung around an object at least the same diameter as the idler wheel on the grinder. Two or four inch long, half-sections of metal duct pipe can be fastened to a board or steel plate. The board or plate can be mounted on a wall next to the grinding equipment. This provides easy belt identification, and proper storage.

Belt Life

The rotation of diamond belts should be alternated when being used. Using a permanent marker, mark the inside new belts with several large arrows indicating the original direction of rotation, prior to initial use. When reinstalling the belt, switch to the opposite rotation direction. It is a good idea to mark the grit and the date of first use, for easy belt identification.

During grinding, the diamond belts will load up with small particles of binder and the ground material, taking on a black color. This "mud" should be removed periodically by steam cleaning the belt.

As it is used, a 966F belt will stop removing chrome efficiently. The grinder current draw will be high, with little chrome removal. These belts will also become capped, and can be dressed in the same method as the diamond belts. If performance is not improved, the belt should be turned around so it rotates in the opposite direction. Rotating the belt allows use of the other leading edge of the belt when traversing the rod, thereby providing more service.

HVOF Prep Equipment

Illustration 43	g06391088
"Stroke Control" Manual Straightening Press

Illustration 44	g06391102
Semi-Automatic Straightening Press

Material preparation (prep) for the HVOF spray salvage process is an important operation regarding the overall coating quality and life.

There are three separate steps for component preparation:

1. Straightening

2. Degreasing

3. Surface Texturing (grit blast)

Straightening

Straightening of all hydraulic cylinder rods and OHT struts Caterpillar currently markets (as of February 1997) would require a 160 Ton press.

The cost of a new 160 Ton press is approximately $100,000 US. The capital cost of straightening presses declines for presses under 100 Tons. Reducing the tonnage of a press will limit the diameter of a component to be straightened.

The current price and availability of new and used presses should be discussed with a press manufacturer or used equipment dealer. The size of a press purchased will be a capital cost versus size limitations trade-off.

The straightening press purchased should be capable of straightening 75% to 90% of the work to be salvaged with the HVOF process. Components that cannot be straightened on the press will have to be straightened by other conventional means.

Eitel presses, located in Orwigsburg, PA is a well-known company in the straightening press business. Eitel presses can be called directly at (717) 366-0585. Their manual stroke-controlled straightening presses will fulfill all the requirements of the Caterpillar HVOF spray salvage program.

Degreasing

A surface that is free from oils and greases is critical to the bonding strength of the spray coating. The following items are chemicals recommended to degrease components prior to grit blasting:

1. Metco Cleaning Solvent

2. Zep Cleaner: ID Red

3. ICI General Chemicals: Triklone LE

4. LPS: ZeroTri

5. LPS: NoFlash

6. Sherwin: Dubl-Chek

7. An Equivalent Degreaser

The main requirement of a degreasing agent will be evaporation from the surface of the component and not leaving behind an oily film.

To test your degreaser, pour a small amount of liquid into a clear glass bowl and let it evaporate. Once evaporated, examine the bowl for any films or residues left behind. If there is a film or residue in the bowl, investigate using a different degreaser.

Degreasing agents should be applied prior to HVOF coating and allowed to evaporate if contamination is a concern.

Grit Blasting

Surface texturing is also critical to the bond strength of the spray coating to the component. A 6.3 µm to 7.5 µm (250 microinch to 300 microinch)Ra surface finish is desired prior to spraying. A random pattern is preferred over a circumferential pattern. The random pattern will increase bond strength and reduce the possibility of crack propagation through the coating by following the substrate and coating boundary.

The grit blast system must be dedicated to the metal spray parts preparation and must not be used for any other shop operation.

The same grit blast system may be used for all thermal spray salvage applications. However, to avoid grit contamination, the system should not be used by any other shop area.

Blast Equipment Options Include:

• Clemco blast room with recycling equipment

• Empire Blast Cabinet Model 4848PRC-6

• PBV-05U-30L-CP Portable Vacuum Recovery

• Pressure Blaster

• Finishers Tech automated blast system

• Progressive Industries automated blast system

Recommended blasting media:

• 20 mesh Aluminum Oxide or equivalent

Using a long nozzle on the blasting equipment can increase the blasting efficiency of the blasting media by maximizing the particle velocity.

Blasting System Improvements:

• A slurry pipe can be used on grit recovery systems to increase the life of the pipe connecting the grit recovery hopper to the pressurized chamber.

• A Schmidt Thompson valve can be added to most grit blast systems. Schmidt Thompson mixing valves have a rugged design that will outlast most OEM mixing valves.

Ventilation

For environmental control and personal safety, proper dust and fume exhaust system are required. EPA (U.S.) rules dictate exhaust system be 99.99% efficient. The recommended system supplier is Torit Downflo Dust Collectors. These systems can be purchased separately or through Oerlikon Metco.

Oerlikon Metco recommends 76 m/min to 91 m/min (250 ft/min to 300 ft/min) air flow across a part being sprayed. A booth with a 1.12 m² (12.00 ft²) opening would require 102 m³/min (3,600 ft³/min).

Show/hide table

NOTICE
Consult your local environmental laws for exact exhaust regulations.

For proper equipment to meet HVOF spray requirements, contact Caterpillar Repair Process Engineering via the following: Cat dealer Technical Communicator, Dealer Solution Network (DSN), Caterpillar Technical Representative, or Knowledge Network .

Refer to Progressive Surface design layouts located under the Tools and Equipment tab

Materials

Every commercially available powder has different coating characteristics of:

• Shrink

• Wearability

• Corrosion Resistance

• Particle Size Distribution

• Composition

• Chemistry

• Flow

Therefore, consider the following criteria when selecting a coating material:

• Engineering material composition, base metal, temperature and environmental factors, and piece part geometry.

• User reliability, performance requirements, versatility, reproducibility, finishing requirements, equipment limitations, and economics.

• Historical application similarities and past application success.

Powder Recommendations

WOKA 7103 powder is the recommended material for chrome replacement. WOKA 7103 has a thickness limitation of 4.6 mm (0.18 inch) per side. The coating shall be deposited in layers of 0.0127 mm (0.0005 inch) per pass. If the total coating thickness is greater than 0.25 mm (0.010 inch), then WOKA 3103 shall be used as a bond/buildup layer. WOKA 3103 has a thickness limitation of 0.76 mm (0.030 inch) and shall be applied in layers of 0.0127 mm (0.0005 inch) per pass.

Based on desirable powder criteria and application development, the WOKA 7103 (Chrome carbide/nickel chromium), WOKA 3103 (Tungsten carbide), and Metco 1008 powders are recommended. These materials offer the following benefits when the HVOF material is applied:

• Allow self-bonding to any clean substrate

• Exhibit a low coefficient of thermal expansion so that thick coatings can be applied

• Offer high internal integrity

• Can be used efficiently and economically

The recommended HVOF spray material for each specific component and application is listed in the component spray procedure document. Table11 provides a list of all HVOF component spray procedure documents.

Powder Parameters

WOKA 7103

Table 11

WOKA 7103 with Propane Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [48]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	240 SLPM (549 SCFH) [38]
Fuel gas pressure	620 kPa (90 psi)
Fuel gas flow	68 SLPM (156 SCFH) [38]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 12

WOKA 7103 with Propylene Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	253 SLPM (578 SCFH) [40]
Fuel gas pressure	689 kPa (100 psi)
Fuel gas flow	70 SLPM (176 SCFH) [40]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 13

WOKA 7103 with Natural Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	360 SLPM (822 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	278 SLPM (635 SCFH) [44]
Fuel gas pressure	758kPa (110 psi)
Fuel gas flow	189 SLPM (432 SCFH) [58]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

WOKA 7103 Increase Deposition

Table 14

WOKA 7103 with Propane Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Orange powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [48]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	240 SLPM (549 SCFH) [38]
Fuel gas pressure	620 kPa (90 psi)
Fuel gas flow	68 SLPM (156 SCFH) [38]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.38 mm (0.015 inch) per side
Laydown rate	0.025 mm (0.001 inch) per pass

Table 15

WOKA 7103 with Propylene Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Orange powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	253 SLPM (578 SCFH) [40]
Fuel gas pressure	689 kPa (100 psi)
Fuel gas flow	70 SLPM (176 SCFH) [40]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.38 mm (0.015 inch) per side
Laydown rate	0.025 mm (0.001 inch) per pass

Table 16

WOKA 7103 with Natural Gas
Spray Material	WOKA 7103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Orange powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	360 SLPM (822 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	278 SLPM (635 SCFH) [44]
Fuel gas pressure	758 kPa (110 psi)
Fuel gas flow	189 SLPM (432 SCFH) [58]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.38 mm (0.015 inch) per side
Laydown rate	0.025 mm (0.001 inch) per pass

WOKA 3103

Table 17

WOKA 3103 with Propane Gas
Spray Material	WOKA 3103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [48]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	240 SLPM (549 SCFH) [38]
Fuel gas pressure	620 kPa (90 psi)
Fuel gas flow	68 SLPM (156 SCFH) [38]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 18

WOKA 3103 with Propylene Gas
Spray Material	WOKA 3103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	375 SLPM (857 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	253 SLPM (578 SCFH) [40]
Fuel gas pressure	689 kPa (100 psi)
Fuel gas flow	70 SLPM (176 SCFH) [40]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 19

WOKA 3103 with Natural Gas
Spray Material	WOKA 3103
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2701
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	689 kPa (100 psi)
Air capacity (Flow meter setting)	360 SLPM (822 SCFH) [46]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	278 SLPM (635 SCFH) [44]
Fuel gas pressure	758 kPa (110 psi)
Fuel gas flow	189 SLPM (432 SCFH) [58]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Metco 1008

Table 20

Metco 1008 with Propane Gas
Spray Material	Metco 1008
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2702
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	724 kPa (105 psi)
Air capacity (Flow meter setting)	399 SLPM (912 SCFH) [50]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	152 SLPM (347 SCFH) [24]
Fuel gas pressure	620 kPa (90 psi)
Fuel gas flow	72 SLPM (165 SCFH) [40]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 21

Metco 1008 with Propylene Gas
Spray Material	Metco 1008
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2702
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	724 kPa (105 psi)
Air capacity (Flow meter setting)	383 SLPM (876 SCFH) [48]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	164 SLPM (375 SCFH) [26]
Fuel gas pressure	689 kPa (100 psi)
Fuel gas flow	70 SLPM (176 SCFH) [40]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Table 22

Metco 1008 with Natural Gas
Spray Material	Metco 1008
Spray equipment type	DJ 2700
Auxiliary cooling	YES
Nozzle assembly	DJ7-9
Distribution plug	DJ2-9
Powder injector tube	DJ8-9
Air cap	2702
Pickup Shaft	"B" pickup shaft
Powder Feed Hose	Blue powder feed hose
Air pressure	724 kPa (105 psi)
Air capacity (Flow meter setting)	319 SLPM (730 SCFH) [40]
Oxygen pressure	1034 kPa (150 psi)
Oxygen flow (Flow meter setting)	189 SLPM (433 SCFH) [30]
Fuel gas pressure	758 kPa (110 psi)
Fuel gas flow	202 SLPM (461 SCFH) [62]
Carrier gas pressure	1035 kPa (150 psi)
Carrier gas flow	13 SLPM (30 SCFH) [55]
Spray rate/build up	75.4 gm/min (10 lb/hr)
Gun to work piece distance	229 mm (9.0 inch)
Rotation speed of part	46-122 SMPM (150-400 SFPM)
Rotation speed of part (RPM)	RPM varies depending on diameter
Traverse rate of gun	5 mm (0.1875 inch) per revolution
Gun fixturing method	Hard mount to traverse apparatus
Thickness limitation	0.51 mm (0.020 inch)
Laydown rate	0.0127 mm (0.0005 inch) per pass

Powder Storage

To prevent powder contamination with moisture, store the powder in a heated cabinet when not in use. Powder contaminated with water will clog feed lines and reduce coating quality.

Cabinet temperature should be kept between 45.0° C (113.00° F) and 65.0° C (149.00° F). A welding rod oven or an old refrigerator modified with a heat lamp can be used to store powders at lower cost than purchasing a heated storage cabinet.

Miscellaneous Support Equipment

The following is a list of equipment that is required to salvage components following the Caterpillar HVOF spray guidelines:

• Surface Analyzer

• Coating Thickness Gauge

• Infrared Thermometer

• Hardness Tester

Surface Analyzer

The following surface analyzers are available through the Caterpillar parts system:

• 448-3697 Indicator Profilometer (M300) and Drive Unit MarSurf RD 18

• 448-3698 Indicator Profilometer (PS10)

Illustration 45	g03507589
448-3697 Indicator Profilometer (M300) and Drive Unit MarSurf RD 18

Illustration 46	g03507627
448-3698 Indicator Profilometer (PS10)

The surface analyzer provides quick, accurate checks of the components being finished, while still chucked or between centers. The analyzer can also provide a paper copy of the final analysis to verify part quality. Use a 5 micron (200 µinch) diamond stylus for measuring, and take multiple measurements at different locations on the rod.

It is important to clean the surface of the rod with 70% isopropyl alcohol before taking any surface measurements, as contamination on the rod will skew the measurement. Also, keep in mind that external vibrations can affect the results.

The OmniSurf software package is available for use with the Indicator Profilometer (M300), and will provide the following features:

• Processing of measured or created profiles

• Graphical presentation of the processed profile in the working area

• Graphical presentation of the loaded or recorded profile in the overview area

• Roughness evaluation of the zoomed profile sections

• Measurement/evaluation of interrupted profiles, excluding profile sections, for example, bores

• Presentation of the aligned profile and the waviness and roughness profiles in separate areas

• Presentation of the altered profile as a result profile

• Storage of the processed profile, i.e. the result, in a file

The recommended Filter Cutoff Selection Options, as used in factory operations, for the OmniSurf software are as follows:

• Short (ls) = 8.0 µm (314.96 µin)

• Roughness (lc) = 0.8000 mm (0.03150 in)

• Bandwidth (lc:Ls) Ratio = 100:1

• Type = Robust

• Spine Tension = Form-Following

• End Region Discard = 1 Cutoff

Coating Thickness Gauge

Illustration 47	g06393604
Elcometer 355 coating thickness gauge

Use of a coating thickness gauge is a quick method to check the thickness of an as sprayed or finished machined coating. The gauge will work on combinations of coatings and base materials where one is magnetic and the other is non-magnetic.

Elcometer makes two thickness gauge models. The 345 is a basic model that will also perform some statistical analysis of the coating measurements. The 355 has a few extra features.

These gauges will work on WOKA 7103 sprayed coatings and on other thermal spray salvage processes.

Contact Elcometer Inc. directly for more information and price inquiries.

Infrared Thermometer

Illustration 48	g06393608
148-2400 Infrared Thermometer

A thermometer is necessary to check the temperature of components during the spray process. The warning temperatures stated in the Salvage Applications should not be ignored for fear of annealing the components being salvaged. Annealing of a component will change the microstructure of the base material, which changes the strength and other material characteristics.

An infrared thermometer will measure the temperature of the component being salvaged without actually touching the surface of the component. IR thermometers measure the temperature of a circular area, emanating in a cone shape from the thermometer tip at an approximate 8:1 ratio. Thus, at a distance of 2.4 m (8.00 ft) from the thermometer, the temperature of a 0.3 m (1.00 ft) diameter circle is indicated.

There are some thermometers that use a contact thermocouple to measure the temperature of a component. The thermocouple can contaminate the surface of the component, thereby reducing the strength and integrity of the thermal spray coating. In addition, contact thermocouples cannot be used during spraying since the part is rotating.

Caterpillar distributes several infrared thermometers through the standard parts distribution system, which are available under the following part numbers:

• 148-2388 Infrared Thermometer

• 148-2400 Infrared Thermometerwith Laser

• 164-3310 Infrared Thermometer Group

• 164-3320 Infrared Thermometer Group (110-Volt, AC Adapter)

Part numbers 148-2400 and 164-3320 have a laser targeting light to aim the thermometer at the component. Both thermometers will provide the required information. However, the 164-3320 can be mounted to the same assembly as the HVOF gun and has the extra features of temperature recording and an overtemp warning signal.

Surface Hardness

Illustration 49	g06393609
Krautkramer Branson MIC 10 Hardness Tester

The surface hardness of chrome to be stripped can easily be checked with a portable hardness tester. The Krautkramer Branson MIC 10 is a unit for fast, accurate, hardness measurements. The unit works by measuring the linear displacement of a pointed probe, which is forced against the test piece.

Masking Aids

Masking aids are used to protect certain areas (threads, bolt holes, etc.) on the substrate from the HVOF and/or surface preparation processes. The protected areas usually require no salvaging or repair.

Masking aids can be divided into four categories:

• Tapes

• Masking compounds (putty)

• Paint

• Permanent masks

Note: At the end of this bulletin, several masking aid suppliers will be listed.

Tapes

Tapes can be used to protect the surface of components for both the HVOF and the surface preparation processes. Masking tapes are a consumable to the salvage process, because they can only be used one time.

Masking a surface for surface preparation with tape can be accomplished in the following manner.

Apply several layers of duct tape or masking tape to the area that requires protection from the grit blasting operation.

Conventional tapes used as a masking aid for the surface preparation process, must be removed prior to the HVOF operation due to their flammable nature.

Masking a surface from the HVOF process with tapes requires a special metal or thermally resistant tape. These tapes are more expensive than conventional tapes, but are easily used to protect areas that have an irregular contour or shape.

Masking Compounds

Masking compounds are a soft conformable putty-like material for masking holes, grooves, key slots, or other unique characteristics. The material is easy to use.

The putty-like material is pressed onto the substrate by hand. After applying the material to a surface for protection, the masking compound must be cured. The amount of heat and required curing time varies depending on the material being used. Average curing cycles are 25 minutes at 121° C (250° F).

Once the material has been cured, it becomes a strong abrasion resistant and thermally resistant material. Following the HVOF process, the material can be cut and removed like a silicone material.

Masking compounds are available in tapes, extruded profiles, and other pre-formed shapes. However, these masking compounds can only be used once.

Paint

Masking paints are applied by brush to a surface for protection. The paint creates a surface barrier that a thermal sprayed coating cannot bond to (similar to a surface that has not been properly prepared). Following the coating operation, the thermal sprayed material can be removed from the painted area.

For thermal spray processes (that is, flame spray and arc spray), paint is a viable masking compound. Paints are not able to withstand the higher temperatures of the HVOF process. As new paints are developed, this section will be updated.

Permanent Masks

Permanent masks are objects or materials that can be used multiple times. These items can be any of the following or a combination of the following:

• Shields placed between the gun and substrate

• Sleeves or collars

• Rubber stoppers (some stoppers will be considered consumables)

• Thermal blanket/insulation materials

• Cutouts (steel or rubber)

Suppliers

Tape

• 3M (contact local representative)

• Furon

• Tape Works

• Greenbelt Industries

Masking Compounds

• Oerlikon Metco

• MachBloc (product of Tape Works)

• Greenbelt Industries

Permanent Masks

• Acme Masking Company

Links to Equipment Information and Suppliers

An HVOF Variable Cost Analysis Worksheet is available on the Repair Process Engineering (RPE) website under the Metal Restoration link. The worksheet automatically calculates variable costs based on information the dealer enters into the program. It utilizes the following categories: Prep Costs (material preparation costs), Spray Costs, and Machining Costs (includes both chrome stripping and HVOF finishing).

Reference: Caterpillar Repair Process Engineering (Metal Restoration)

https://dealer.cat.com/en/ps/service/rpe/c/metal-restoration.html

Reference: 3M

www.3m.com

Reference: Torit Products

P.O. Box 1299
1400 West 94th Street
Minneapolis, Minnesota 55440
1 (800) 365-1331
www2.donaldson.com/torit

Reference: Oerlikon Metco

www.oerlikon.com/metco

Reference: TAFA

www.praxair.com/thermalspray

Reference: Eitel Presses

www.eitelpresses.com

Reference: Progressive Surface

4695 Danvers Drive SE
Grand Rapids, Michigan 49512
1 (616) 285-8390
www.progressivesurface.com

Reference: Abbott Machine Co.

700 W. Broadway
Alton, IL 62002
1 (618) 465-1898
1 (800) 262-6478
www.abbottmachineco.com

Reference: Supfina

Schmelzergrun 7
77709 Wolfach, Germany
49 (7834) 866-0
www.supfina.com

Reference: IMPCO Machine Tools

3417 West St. Joseph Street
Lansing, Michigan 48917
1 (517) 484-9411
www.impco.com

Reference: Grinding Equipment & Machinery Company, LLC

15 South Worthington Street
Youngstown, Ohio 44502
1 (330) 747-2313
www.gem-usa.com

Reference: Oberlin Filter Company

404 Pilot Ct.
Waukesah, WI 53188
1 (262) 547-4900
www.oberlinfilter.com

Reference: Schmidt Manufacturing Inc.

P.O. Box 37
Fresno, Texas 77545
1 (713) 431-0581
Fax: 1(713) 431-1717

Reference: Elcometer Inc.

1893 Rochester Industrial Drive
Rochester Hills, Michigan 48309
(810) 650-0500 or
1-800-521-0635
Fax: (810) 650-0501

Reference: Krautkramer Branson

600 N. Shepherd Drive, Suite 115
Houston, TX 77007
(713) 861-3270
Fax (713) 861-4784
http://www.stroudsystems.com

Reference: Furon

1 (508) 686-7301

Reference: Tape Works

2285 Avenue A
Bethlehem, Pennsylvania 18017
1 (800) 752-1125
1 (610) 264-5115
www.tape-works.com

Reference: Acme Masking Company

240 South Production Drive
Avon, Indiana 46123
1 (317) 272-6202

Reference: Greenbelt Industries

45 Comet Street
Buffalo, New York 14216
1 (800) 668-1114