Effect of MoB2 Content on the Microstructure and Wear Resistance of NiCr Coatings by Laser Cladding

The aim of this study is to investigate the mechanism of the influence of different contents of ceramic-reinforced particles MoB₂ on the microstructure, microhardness, and wear resistance of NiCr coatings. The x (MoB₂)-NiCr composite coatings with varying MoB₂ contents (x = 0,1,5,10, and 15 wt%) were applied to 304 steel using laser cladding. The results suggest the composite coatings consist of γ-(Ni, Cr), γ-(Ni, Fe), Ni_2.9Cr_0.7Fe_0.36, and MoB₂. The hardness of the composite coatings gradually increased as the MoB₂ content increased. The highest average hardness of the composite coatings was achieved when 15 wt% MoB₂ was added, reaching 485.5HV_0.1, which was 61.5% higher than the NiCr coating without MoB₂. The wear resistance of the composite coatings exhibited an initial enhancement followed by a decrease with the MoB₂ content increased. The 10 wt% MoB₂-NiCr coating exhibited the highest wear resistance, and the wear rate decreased by 75.5% compared with the NiCr coating without MoB₂. The wear mechanism of the coatings changed from severe fatigue and adhesive wear to slight abrasive and oxidative wear with the increase of MoB₂.