Functional Gradient Coatings for Landing Gear

HVOF as a Hard chrome replacement on landing gears has proven to be very successful but there still are some challenges that have not been overcome.ááThere are limitations to HVOF coating thickness and to parts with high bending stresses which may cause the HVOF coating to spall in-service.ááThe current limitation on thickness is 0.010 inches and the current limit on bending stress is the yield strength of the substrate material.ááDuring overhaul of landing gear components functional areas of the landing gear may require HVOF coating thickness beyond the 0.010 inches which is currently not approved, therefore leaving the landing gear part in an unrepairable condition.ááFor landing gear parts with high bending stresses chrome plate is being used. The chrome plating process produces Hexavalent Chrome which is a known carcinogen, and this process is under tight Personal Exposure Limit (PEL) and is slowly being eliminated from the aerospace arena.ááA HVOF coating system that would allow for thicker repairs and use on high bending stressed landing gear parts would allow for near 100% elimination of line-of-sight chrome plate at Hill AFB landing gear repair center.