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首页> 美国政府科技报告 >Validation of HVOF Thermal Spray Coatings as a Replacement for Hard Chrome Plating on Hydraulic/Pneumatic Actuators
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Validation of HVOF Thermal Spray Coatings as a Replacement for Hard Chrome Plating on Hydraulic/Pneumatic Actuators

机译：验证HVOF热喷涂涂层作为液压/气动执行器上硬镀铬的替代品

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Electrolytic hard chrome (EHC) plating is a technique that has been in commercial production for over 50 years. It is a critical process that is used both for applying hard coatings to a variety of aircraft components in manufacturing operations and for general re-build of worn or corroded components that have been removed from aircraft during overhaul. Chromium plating baths contain chromic acid, in which the chromium is in the hexavalent state, with hexavalent chromium (hex-Cr or Cr6+) being a known carcinogen. During operation, chrome plating tanks emit a hex-Cr mist into the air, which must be ducted away and removed by scrubbers. Wastes generated from plating operations must be disposed of as hazardous waste and plating operations must abide by U.S. Environmental Protection Agency (EPA) emissions standards and Occupational Safety and Health Administration (OSHA) permissible exposure limits (PEL). High-velocity oxygen-fuel (HVOF) thermal spray technology can be used to deposit both metal alloy coatings and ceramic/metals (cermets) such as tungsten carbide/cobalt (WC/Co) that are dense and highly adherent to the base material. Previous research, development and validation efforts had established HVOF thermal spray coatings as the leading candidates for replacement of hard chrome. This led to industry acceptance of HVOF WC/CoCr and WC/Co in place of hard chrome for landing gear, to the point that landing gear on most new aircraft designs are now specified with HVOF. In addition, in overhaul operations these coatings can be built up to thicknesses needed for dimensional restoration, as is currently done with EHC. HVOF systems are commercially available and installed in several depots, and there are numerous commercial vendors supplying the OEM community. Although HVOF coatings are now coming into wide use for landing gear, their qualification as an acceptable replacement for EHC plating on actuators has not been adequately demonstrated.

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