HIGH VELOCITY OXY-FUEL THERMAL SPRAY
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| Overview: | High Velocity Oxy-Fuel (HVOF)
thermal spray technology is a dry process that produces a dense metal
coating whose desired physical properties are equal to or surpass those of
hard chrome plating (HCP). These properties include wear resistance,
corrosion resistance, low oxide content, low stress, low porosity, and
high bonding strength to the base metal.
HVOF thermal spray uses a fuel (i.e., propylene, hydrogen, propane, kerosene)/oxygen mixture in a combustion chamber. This combustion process melts a metal powder that is continually fed into a gun using a carrier gas (argon) and propels it at high speeds (3,000 - 4,000 ft/sec) towards the surface of the part to be coated. The high speed of the spray produces a coating upon impact that can be used as an alternative to the HCP process. The metal powder is available in many compositions, including: nickel, nichrome, inconel, chrome carbide, and tungsten carbide. Uniform coating thickness of up to 0.250 inches can be achieved. The only waste stream produced by HVOF is from the capture of the overspray. Current systems use a dry cartridge filter system with an optional high efficiency particulate air (HEPA) filter. Since the overspray contains only the pure metal or alloy, it is feasible to recycle or reclaim this waste stream. | |||||||||||||||||||||||||||
| Compliance Benefit: | This process melts a metal powder and produces
a dense metallic coating with physical properties are equal to
or surpassing those of HCP. The only waste stream produced
by HVOF is from the capture of the overspray. Since the overspray contains
only the pure metal or alloy, it is feasible to recycle or reclaim this
waste stream. Traditional plating operations generate a large volume of
hazardous waste from contaminated plating bath solutions and rinse waters.
The reduction of hazardous waste helps facilities meet the requirements of waste reduction under RCRA, 40 CFR 262, Appendix, and may also help facilities reduce their generator status and lessen the amount of regulations (i.e., recordkeeping, reporting, inspections, transportation, accumulation time, emergency prevention and preparedness, emergency response) they are required to comply with under RCRA, 40 CFR 262. In addition, since bath solutions are eliminated (i.e., less sulfuric acid and chromic acid) there is less chance that the facility would exceed reporting thresholds for hazardous substances/chemicals under SARA Title III (40 CFR 300, 355, 370, and 372; and EO 12856). The elimination of hard and decorative chromium electroplating from a facility may also decrease the need for meeting NESHAP requirements under 40 CFR 63.340 - 63.347 and for an air permit under 40 CFR 70 and 40 CFR 71. It should be noted that a new air emission may result from the use of this new technology. Additionally, this technology uses considerably less water than the traditional electroplating operations and as required under EO 12902, Energy Efficiency and Water Conservation at Federal Facilities. The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved. | |||||||||||||||||||||||||||
| Materials Compatibility: | No materials compatibility
issues were identified.
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| Safety and Health: | When working with fine particulate matter that
consists of various compositions of different metals, inhalation is a primary
concern. Proper personal protective equipment should be used.
Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing this technology. | |||||||||||||||||||||||||||
| Benefits: |
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| Disadvantages: |
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| Economic Analysis: | The cost for implementing HVOF (in lieu of
continuing to use HCP to apply a surface coating to production parts) depends
on many variables, in particular the following:
The following cost comparison uses figures from Norfolk Naval Shipyard, in Portsmouth, VA. Assumptions:
Cost Comparison for HVOF vs. HCP Technologies
Economic Analysis Summary
Click Here to view an Active Spreadsheet for this Economic Analysis and Enter Your Own Values. To return from the Active Spreadsheet, click the Back arrow in the Tool Bar. | |||||||||||||||||||||||||||
| NSN/MSDS: |
*There are multiple MSDSs for most NSNs. The MSDS (if shown above) is only meant to serve as an example. To return from the MSDS, click the Back arrow on the Tool Bar. | |||||||||||||||||||||||||||
| Approving Authority: | Appropriate authority for making process
changes should always be sought and obtained prior to procuring or implementing any of the
technologies identified herein.
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Points of Contact: |
For more information
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Vendors: |
This is not meant to be a complete list, as there may be
other suppliers of this type of equipment.
Praxair TAFA
Sulzer Metco (US) Inc. | |||||||||||||||||||||||||||
| Related Links: |
Replacement of Chromium Electroplating Using HVOF Thermal Spray Coatings |
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| Sources: | None listed. |
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| Supplemental: |
Picture of Chromium Replacement Using
High Velocity Oxygen Fuel Thermal Spray Coating
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