Non-Line of Sight Coating on High Strength Steel Substrate

ABSTRACT: Electrolytic Hard Chrome (EHC) has been used in both civilian and military aerospace as the hard wear resistant coating of choice for both high strength and low strength steels. Due to tighter regulations there is a current requirement to eliminate the use of EHC on landing gear components for Air Force applications. There are many benefits to EHC such as providing an excellent wear surface, a good corrosion barrier and it allows for surface restoration to dimensional tolerances during the repair and overhaul process. EHC also provides a good sealing surface for hydraulic fluid. However, due to EHC environmental and health hazard risks due to the presence of Hexavalent Chrome, the Under Secretary of Defense has directed all DOD Military Departments to invest in appropriate research and development on EHC substitutes and approve the use of alternatives where they can perform adequately for the intended application. USAF has been implementing HVOF thermal spray coatings on HSS landing gear line of sight applications (ODs) for several years. However, landing gear components still use EHC on non-line of sight areas and is in need of technology which will replace EHC for this application. ES3 successfully completed a Phase I feasibility study that demonstrated the ability to apply coatings to non-line of sight surfaces of HSS landing gear components. Of the three coating technologies investigate in Phase I there are two technologies that will be explored for full optimization during Phase II. Magnetron Sputter HVOF-ID The objective of this effort is to develop and optimize coating systems that can replace EHC platings on non-line of sight surfaces of HSS substrates. More specifically, numerous tests will be performed on the applied coatings to show that they posses the qualities necessary to make an acceptable coating. The optimized coatings and systems can be specified for standard maintenance at USAF Air Logistic Centers (ALC"s) and Navy Air Depots. BENEFIT: Research conducted to develop a coating process which can restore HSS non-line of sight surfaces of worn or damaged land gear components, focuses on military applications; however, benefits will be similar for all commercial & military landing gear that need IDs restored to original dimensions. ES3 expects the following benefits from the Magnetron Sputter or HVOF ID systems restoring the non-line of sight surfaces of HSS landing gear components based on both industry and in-house research: Non-line of sight surfaces of worn or damage assets can be restored to serviceable condition in place of EHC. Increased supportability of steel landing gear parts for USAF and commercial industry Reduction in ownership cost for the USAF and commercial industry Processes could be used to repair other aircraft parts including hydraulics