Effect of VN alloy addition on the microstructure and wear resistance of Co-based alloy coatings

VN alloy/Co-based composite coatings were prepared on the mild steel substrate by laser cladding. The effect of different amounts of VN alloy on the microstructure and wear resistance of Co-based coatings was investigated systematically by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, micro hardness testing and wear testing. The results showed phases of Co-based cladding coatings after adding VN alloy were gamma-Co, Cr23C6, Co5.47N, sigma-FeV and VN. A certain amount of fine grains and polygonal equiaxed grains synthesized as well as dense stacking fault and interaction of stacking fault were formed after adding VN alloy. The microhardness and wear resistance of coatings both improved greatly with a moderate additional amount of VN alloy. The improvement in microhardness and the reduction in wear loss were 12.0% and 36.4%, respectively, for 5.0 wt.% VN alloy, and the wear mechanism was abrasive wear. Thus, it is concluded that adding VN alloy is an effective and attainable way to improve the wear resistance of Co-based coatings. (C) 2015 Elsevier B.V. All rights reserved.