The effects of boron on in-situ phase evolution and wear resistance of wide-band laser clad nickel composite coatings

In this paper, the Ni60/WC composite coatings were prepared by wide-band laser cladding technology. The effects of B addition on the microstructure and properties of composite coatings were studied by microstructure characterization, phase identification, microhardness, and wear resistance. The results show that the in situ-synthesized phases in laser molten pool were mainly composed of gamma-Ni solid solution, CrB, Cr5B3, Cr7C3, Cr23C6, and other intermetallic compounds. With the increase of B content in the composite cladding layer, the formation of the CrB compound was inhibited and the formation of the Cr5B3 reinforcing phase was promoted. When the B content reaches 4 wt%, the number of Cr5B3 in the cladding layer increases obviously, and the morphology changes from regular rhombus to thicker strip. The analysis of wear surface morphology shows that the increase of strip brittle Cr5B3 phase increases the spalling of strengthening phase under wear load, which increases the friction coefficient of the cladding layer and reduces the wear resistance of the composite coating. It can be concluded that the alloying effect of B changed the composition and morphology of the reinforced phase in the nickel-based composite cladding layer. As the mass fraction of B reached 1 wt% in composite coating, the microhardness of the cladding layer reaches 879 HV, the friction coefficient and wear weight loss are both at a low level. The comprehensive performance of this coating shows the best in the experiment group.