Effect of WC on Microstructure, Wear Resistance and Impact Resistance of Laser Cladding Layer

Laser cladding Ni based alloy coating has good comprehensive properties, but the wear resistance and impact resistance still need to be improved. Therefore, WC/Ni coatings were prepared by laser cladding of Ni based powders containing micro and nano WC particles respectively, and the effects of WC particles on the microstructure, wear resistance and impact resistance of Ni based coatings were studied. The SEM and XRD were used to analyze the microstructure of the composite coating. The high-speed camera was used to analyze the shape of the molten pool during the cladding process. Wear tester and charpy impact tester were used to test the wear resistance and impact resistance of the composite coatings. The effect of nano WC on the molten pool flow is stronger than that of micro WC, and the microstructure of the coating is more refined. Due to the close combination of micro-WC and Ni45 coating, it can effectively resist the cutting of asperity in wear test, and finally significantly enhance the wear resistance of the coating, and the wear rate is 88.38% lower than that of the Ni45 coating. However, the high brittleness of micro-WC is not conducive to the improvement of impact resistance, the impact toughness is only 91.28% of the Ni45 coating. the wear rate of the nano-WC coating is 53.43% lower than that of the Ni45 coating because the nano WC particles are dispersed in the grain boundary and eutectic region while refining the grain, which hinders the movement of dislocations and inhibits the plastic deformation of the grain. Due to the nano WC in the grain boundary and eutectic region will hinder the crack propagation and change the propagation direction, thus increasing the energy of forming through cracks and the impact energy required for coating fracture, and significantly improving the impact toughness of the coating. The impact toughness of the coating is 13.37% higher than that of Ni45 coating. Through the finite element analysis, it can be seen that the micro-WC in the coating will form high stress concentration during the impact process, which proves that it has adverse effects on the impact resistance of the coating. However, nano WC can reduce the uneven slip of dislocations, alleviate the accumulation of dislocations, and effectively disperse the stress concentration formed in the impact process of the coating, which proves that it can significantly improve the impact resistance of the composite coating. The results show that nano WC can improve the wear resistance and impact resistance simultaneously.