Study on Interfacial Characteristics and Tribological Behavior of Laser Cladding Ni/WC Coating

Ni60/WC composite coatings reinforced with various WC contents were fabricated on 45 steels via high-speed laser cladding. First-principles calculations were adopted to investigate the interfacial characteristics between Ni and WC. The microstructures of the coating were analyzed by a scanning electron microscope (SEM). The microhardness and wear resistance of the coatings were evaluated by a Vickers hardness tester and a friction and wear tester. Theoretical calculations indicate that the C-terminated WC (001) crystal plane achieves the most stable bonding with the Ni (111) surface through the hcp site, with an interface energy of 9.57 J·m−2. The interface is mainly provided by Ni-W metal bonds and Ni-C covalent bonds. The microstructure results show that the WC particles have good metallurgical bonding with the Ni matrix. Thus, the good interface ensures efficient load transfer to hard WC particles. The microhardness rose markedly with the increase in WC content, reaching 760 HV0.2 for the 40 wt.% WC, which is 1.8 times that of Ni60 coatings. Tribological experiments showed that appropriate WC content could significantly improve the wear resistance of the coating.