Microstructure and mechanical properties of WC particle reinforced Ni-based composite coatings

To resolve the problem of WC particle delamination and decomposition during the preparation of the composite coatings, the WC particles and Ni-based alloy composite powders were employed to fabricate the WC particle reinforced Ni-based composite coatings by laser cladding technology on 34MnB5 steels. The effect of cladding power on the microstructure and properties of the coatings was systematically investigated. The microstructure and phase composition of the powders and coatings were characterized by optical microscope, scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer. The layer thickness and WC volume fraction were measured by Image J software, while the hardness and tribological properties were evaluated by microhardness testing and ASTM G65 standard wear experiments. The results show that the hardness and surface morphology of the composite coatings are significantly improved with increasing cladding power, however, the WC volume fraction in coatings is decreased from 41.6% to 30.2%. When the cladding power is high, the overheating may lead to the decomposition of WC particles to form free C and W atoms, which can be dissolved into the Ni-based matrix or formed W-rich carbides lead to the hardness elevating of the matrix. The tribological properties testing show that the wear resistance is positively correlated with the volume fraction of WC particles under low-stress abrasion condition. So, the wear resistance of the composite coatings is preferred when the cladding power is 1.4 kW. However, when the cladding power is 1.8 kW, there is almost no cracks and higher surface quality, which is suitable for applications on the balancing condition of surface qualities and impact resistance.