Effect of Ti on the microstructure evolution and wear behavior of VN alloy/Co-based composite coatings by laser cladding

VN alloy/Co-based composite coatings modified by Ti was prepared on a mild steel using laser cladding. The effect of Ti addition on the microstructure and wear resistance of VN alloy/Co-based coatings was investigated using optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, micro hardness tester and wear tester. The results showed that TiN and VC phases were detected in the VN alloy/Co-based composite coatings after adding Ti, in addition to gamma-Co, Cr23C6 and sigma-FeV phases. Massive short rod-like dendrites, equiaxed grains and fine grains appeared in the composite coatings after adding Ti, and the cross-slip and jog of the dislocation disappeared. The microhardness of the composte coatings was increased significantly with the increase of additive Ti, and was improved by 21.6%, for 9.6 wt.% Ti addition. The wear resitance of the composite coatings was firstly increased and thereafter decreased with the increase of additive Ti, and was improved by 25.9%, for 4.8 wt.% Ti addition. The abrasive mechanism of the composite coatings after adding Ti was the abrasive wear. Thus, it can be concluded that adding Ti effectively promotes the formation of TiN and VC particles to improve the wear resistance of the composite coatings.