Microstructures and properties of TiN reinforced Co-based composite coatings modified with Y2O3 by laser cladding on Ti–6Al–4V alloy

Abstract

In this study, TiN reinforced composite coatings were fabricated on Ti–6Al–4V substrate by laser cladding with Co42 self-fluxing alloy, TiN and Y2O3 mixed powders. Microstructures and wear resistance of the cladding coatings with and without Y2O3 addition were investigated comparatively. Results showed that the coatings were mainly comprised of γ-Co/Ni, TiN, CoTi, CoTi2, NiTi, TiC, Cr7C3, TiB, Ti5Si3 and TiC0.3N0.7 phases. The coatings showed metallurgical bonding free of pores and cracks with the substrate. Compared with the Ti–6Al–4V substrate, the microhardness and wear resistance of the coatings was enhanced by 3–4 times and 9.5–11.9 times, respectively. With 1.0 wt.% Y2O3 addition, the microstructure of the coating was refined significantly, and the microhardness and dry sliding wear resistance were enhanced further. The effects of Y2O3 were attributed to the residual Y2O3 and decomposed Y atoms.