In-situ reinforced phase evolution and wear resistance of nickel-based composite coatings fabricated by wide-band laser cladding with Nb addition

In this paper, Ni60/WC composite coatings were prepared by wide-band laser cladding technique. The effects of the addition of the strong carbide forming element Nb on the microstructure and properties of the composite coatings were studied by microstructure characterization, phase identification, microhardness, wear resistance, and other properties. The results show that the in-situ synthesized phases in the laser molten pool are mainly composed of gamma-Ni solid solution and strengthening phases such as Cr7C3, Cr23C6, Cr5B3, and NbC. With the increase of Nb content in the composite cladding layer, the formation of Cr7C3 is inhibited, the amount of residual WC decreases, while the content of NbC increases, and the morphology of the precipitated phase containing NbC changes from coarse strips to fine needle-like agglomerates and then to blocky. Among them, when the Nb content reaches 3 wt%, the needle-like agglomerated NbC is uniformly distributed and has good adhesion to the substrate, which can effectively reduce the breakage and shedding of the hard phase during the wear process and has the best wear resistance performance. Overall, the alloying effect of Nb changed the composition and morphology of the strengthening phase in the cladding layer of the nickel-based composites, reducing the hardness of the cladding layer but enhancing the microstructure uniformity, resulting in improved wear resistance of the coating.