Modification of Cold-Sprayed Cu-Al-Ni-Al2O3 Composite Coatings by Friction Stir Technique to Enhance Wear Resistance Performance

An innovative hybrid process combining two effective surface modification techniques, cold spray (CS) and friction stir processing (FSP), was proposed to refine the microstructure of Cu-Al-Ni-Al2O3 composite coating material. FSP was performed under constant rpm using extensive cooling conditions to remove heat generated during the operation. Microstructural characterizations such as optical micrography (OM), scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were performed to evaluate the microstructural evolution of the coatings before and after FSP treatment. Mechanical characterizations such as microhardness and elastic modulus were measured using micro-depth sensing techniques. Furthermore, sliding wear tests were performed to study the wear resistance of the as-sprayed and processed coatings. The findings suggest that after FSP, there is an improvement in microstructure of the coating layers with the elimination of particle boundaries, micro-pores and micro-cracks, and processed coatings showed an improvement in mechanical properties. Furthermore, there was a slight reduction in the wear rate of the deposited CuAlNi-Al2O3 composite coatings. Among all the test coatings, friction stir processed S1 coating showed the lowest wear rate, which was an almost two times lower wear rate than its unprocessed counterparts.