High performance protective coatings on the inner diameter of landing gear components for the replacement of hard chrome: assessment and predictive modeling of fatigue behavior

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Heavy duty components are often plated with a hard layer of chrome, called electrolytic hard chrome, to improve the part performance. Producing such plating through the use of hexavalent chrome is not safe from a health and environmental point of view and the ever increasing regulatory requirements push the development of alternative process and alloys. An alternative is a tungsten-carbide coating applied by High Velocity Oxy-Fuel (HVOF) thermal spraying. They have increasingly replaced electrolytic hard chrome plating on landing gears, helicopter dynamic components, propeller hubs, and hydraulic actuators. Those sprayed coatings tend to provide superior wear, corrosion and fatigue performance than electrolytic hard chrome plating, yielding direct cost benefits for both the coating applicator and the aerospace manufacturer. However, the technology cannot be readily translated to confined internal surfaces or difficult to reach areas of complex shapes, such as the smaller internal diameters. The aim of this proposal and partnership is to advance the technological maturity of inner-diameter (ID) HVOF carbide coatings. As part of a wider initiative, the present objectives are to define the processing domain of ID-HVOF as a function of the required powder feedstocks and coating properties, predict their microstructure, characterize and describe the fatigue behaviour of the coating/substrate assemblies and in-service behaviour. Data-analytic tools will be used to increase the process robustness. The potential outcomes of this research project include a new high value-added coating technology for deep bore parts and difficult to reach surfaces, a methodology to understand and predict in-service performance for such parts and a process control strategy meeting Industry 4.0 expectations. The outcomes of this project will benefit Canadian companies encompassing the entire value chain of material suppliers, equipment providers, coating applicators and original equipment manufacturers in producing higher performing components, reducing the environmental impact of the manufacturing operations, and being part of a step-change technology of global impact.