Effect of Y on microstructure of laser clad coatings reinforced by in situ synthesized TiB and TiC

Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles were fabricated on Ti6Al4V by laser cladding. The effect of rare earth Y addition on microstructure of the coatings was investigated by means of X-ray Diffraction (XRD), Optical Microscope (OM), Scanning Electron Microscopy (SEM) and Electron Probe Micro-Analysis (EPMA). The results show that the coatings with Y mainly consist of a great amount of α-Ti cellular dendrites and few coarse/fine needle-shaped TiB, equiaxial TiC and spherical Y2O3 particles. A small amount of Y (1–3 wt.%) added to the coatings can refine the microstructure, improve the microstructural uniformity and increase the volume fraction of eutectics, which will endow the coatings with more excellent mechanical properties, such as higher strength, microhardness and toughness. When the addition content of Y varies from 2 wt.% to 3 wt.%, the microstructure of the coatings presents no significant difference except that the volume fraction of eutectics is increased gradually.