A novel method to fabricate Ni/WC composite coatings by laser wire deposition: processing characteristics, microstructural evolution and mechanical properties under different wire transfer modes

Abstract A novel method for the additive manufacturing of Ni/WC composite coatings via laser wire deposition is introduced in this work. The processing characteristics of the typical wire transfer modes, including the liquid spreading transfer mode, wire plunging transfer mode, and wire stubbing transfer mode, were analyzed by a high-speed camera system. The phase compositions and microstructural features were clarified by material characterization methods, including X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The dissolution mechanism of the ceramic particles and the microstructural evolution of the coatings obtained under these three wire transfer modes are also discussed. The hardness and wear resistance of the coatings were evaluated using a microhardness tester and a dry sliding wear tester. The results showed that laser deposition with wire plunging transfer mode could effectively avoid the burning and sinking of the ceramic particles in the coatings, resulting a continuous coating with a high volume fraction of retained particles and a low degree of dilution. The coating had a uniform microstructure which was primarily composited of Ni-based solid solution matrix, retained WC/W2C particles, in-situ synthesized WC, M6C, and Ni/Ni3B lamellar eutectic structure. The coating fabricated with wire plunging transfer mode possessed higher hardness and minimum wear loss.