MULTIFUNCTIONAL FUNCTIONALLY GRADED COATINGS FOR LANDING GEARS

The desire to remanufacture the complex structural components of aircraft landing gear along with the strict tribological, corrosion, loading, and fatigue performance requirements of the surfaces in these systems present a distinct materials, process, and design challenge. To achieve both the desired dimensional restoration and the surface functionality required by this application, a Functionally Graded Coating is proposed here consisting of an initial bond layer followed by a thick graded build layer with a composition that continuously varies into a qualified WC-CoCr protective surface coating. The design strategy proposed will be realized through several manufacturing and property control innovations that includes the development of a closed loop dual injection powder feed system for the high velocity oxy-fuel deposition process along with the dynamic measurement of particle behavior and stress states. Design specific consideration for each of the coating layers includes the through thickness variation in residual stress state and coating composition along with thermal and mechanical properties. As each of these design considerations is highly dependent on a number of manufacturing process variables, additional novel process control and feedback strategies will be utilized, employing in-situ measurements of the residual stresses formed during the deposition process and the radiative characteristics of the molten particle spray stream. This will allow both through-thickness tailoring of the desired chemistry along with stress-states so as to enable multifunctional capabilities of the coating to meet both structural and surface functionalities.á These attributes can further be integrated into an Integrated Computational Materials Engineering framework tailored for landing gear coating design that can be used to simultaneously optimize design relevant coating parameters and make predictions of cracking and delamination under operation relevant loading cycles.á ???????