Ti-based composite coatings with gradient TiC x reinforcements on TC4 titanium alloy prepared by laser cladding

TiC _x -NiTi₂/Ti cermet composite coatings C1 and C2 with gradient TiC _x reinforcements were prepared on TC4 titanium alloy by laser cladding method. The microstructure and phase compositions were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) meter. The TiC _x exhibited a dendritic microstructure, and homogeneously dispersed in the Ti-based matrix where NiTi₂ was embedded. With increasing ingredient supercooling, temperature gradient and cooling temperature, the dendrites displayed a finer morphology with longer primary trunks and intensified side branches in the dilution zone. But the smoothed, coarse columnar ones became dominant in the upper clad layer due to the repeated energy input during multi-track cladding. The Vickers microhardness presented a linear change trend through the cross-sections, which well confirmed the gradient distribution of TiC _x . With more TiC _x , C1 presented higher hardness than C2.