Wear Resistant Coatings for Aluminum and Titanium Alloy Housings and Flanges

Aluminum and titanium alloys have become more widely used for bearing housings and flanges in aerospace propulsion systems because of their low density, high strength-to-weight ratio, and high thermal conductivity. However, their wear resistance and corrosion resistance are poor. When matched to harder steel surfaces under adverse vibrations, loads, and temperature cycling, they can experience a significant fretting wear. Currently, steel inserts or bushings are employed to solve the fretting wear of aluminum alloy components. However, such approach increases a number of manufactured parts and decreases the strength-to-weight ratio of the entire mechanisms. The mismatches of thermal and mechanical properties at the interface will largely affect the functionality of whole housing and flange system. Boston Applied Technologies Incorporated (BATI) proposes to develop an innovative wear resistant, hard coating to replace the steel inserts and bushings. The proposed coatings are grown from aluminum or titanium alloy substrates utilizing the microarc-discharge oxidation followed spraying process. The coatings will have a thickness of up to 200 µm and unique cross-sectional microstructure and phase composition. The inner layer metallurgically binds with substrate alloys and thus exhibits high adhesion strength, and the outer layer exhibits low fraction coefficient and good wear resistant in contact with steel, and also good corrosion resistance. The proposed approach does not affect the bulk mechanical characteristics of bearing housing and flange systems, and yet at a low-cost.