Development of Pulse Water Strip of Tungsten Carbide HVOF Coatings and Chrome Plating on Landing Gear Components

Chrome plating has been utilized as a protective wear coating for High Strength Steel (HSS) and Low Strength Steel (LSS) aircraft components for over half a century. High Velocity Oxygen Fuel (HVOF) tungsten carbide chrome (WC-Co or WC-Co-Cr) coatings are currently being utilized as a chrome replacement on many aerospace and commercial components. Chrome plating and HVOF coatings are stripped using wet chemical baths at overhaul. Both processes require different chemical solutions that are hazardous to personnel and could possibly damaged the component(s) during the stripping process. Phase I testing demonstrated that Force Pulse Water Jet (FPWJ) processing technique could in fact remove chrome plating and HVOF coatings from 4340 and 300M steel substrates. Both hard chrome and HVOF coatings were successfully removed with no damage to the substrate, and maintained an excellent finish. Further testing will be conducted in Phase II to validate the fatigue and crack detection characteristics of the FPWJ process. Fatigue and crack detection testing will determine if FPWJ stripping process causes a fatigue debit, a loss of peening intensity, or covers potential cracks. Recommended FPWJ stripping parameters and booth design will also be developed during Phase II. BENEFIT: The research discovered from removing chrome plating and HVOF tungsten carbide coatings on Aircraft, Engine and Propeller, and Landing Gear components will benefit the military and commercial world usage of high strength steel materials, such as 300M (280-300 KSI) and low strength steel materials such as 4340 (180-200). The benefits of the FPWJ strip method will be similar for all Aircraft, Landing Gear, Engine, and Propeller components when implementing this system into overhaul. ES3 expects the following benefits from use of the FPWJ strip system on chrome plating and HVOF (WC-Co or WC-Co-Cr) coatings, based on both industry and in-house research: • Utilization of one FPWJ strip system in lieu of two separate wet chemical baths for the removal of both chrome plating and HVOF coatings. • Elimination of hydrogen embrittlement. • Elimination of arc burn damage. • Improvement of environmental concerns. • Elimination of relief bakes. • Improved process times. • Utilization of basic water (no abrasives) in a recycled system.