Abstract: Ni-WB₂ composite clad layer was prepared on the 45 steel substrate through vacuum cladding technology. The microstructure of the clad layer was characterized by means of SEM, EDS and XRD, and wear performance was studied by using pin-disc type wear apparatus. The results show that the Ni-WB₂ composite clad layer is dense, and a strong metallurgical bond formed at the interface between the clad layer and the substrate. The clad layer can be subdivided into reticular zone, transition zone and diffusion zone based on its microstructure, and the reticular composite zone is divided into area Ⅰ and area Ⅱ. The diffusion zone is mainly composed of Fe-based solid solution and Ni-based solid solution. The main phases of the transition zone are γ-Ni and chromium carbide, and the main compositions of the reticular composite zone are Ni-based alloy, chromium carbide, WB₂, nickel silicon eutectic and complex comppund formed owing to the chemical combination between the WB₂ and elements of nickel-based alloy. When the WB₂ content is lower than 20%, both the wear rate and friction factor of the Ni-WB₂ composite clad layer decrease gradually with the increase of WB₂ content. When the WB₂ content is 15%, the wear rate and friction factor of Ni-WB₂ composite clad layer decrease by 48.94% and 14.62% respectively compared with that of the 45 steel substrate. During the wear process, the load supporting effect of the hard phase with network distribution and the formation of WO_x oxide are conducive to reduce the friction and wear of the Ni-WB₂ composite clad layer.

Key words: vacuum cladding technology, Ni-WB₂ composite clad layer, network composite coating, friction and wear behavior