Effect of LaB6 addition on the in-situ synthesis of TiB /Ti Ni /TiC reinforced Ni-based composite coatings

The TiBx/TixNiy/TiC reinforced Ni60 composite coatings were successfully prepared on the surface of 35CrMoV substrate using the laser cladding technology by adding different content of LaB6 (0, 0.5, 1.5, 2.5 wt%) powders into the mixture of TC4 (Ti6Al4V) and Ni60 (94 wt% Ni60, 6 wt% TC4). The phase composition, microstructure, element distribution and chemical composition of the cladding layer were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) with energy spectrum analysis (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The reinforced phases in the cladding layer were mainly composed of TiB2, TiC, TiB, Ti2Ni, NiTi and Ni3Ti. The addition of LaB6 did not affect the phase composition, but the grains are obviously refined and the distribution of Ni, Cr and Ti elements is uniform at the addition of 1.5 wt% LaB6 addition. The cladding layer obtained excellent tribological and mechanical performance with the addition of 1.5 wt% LaB6, and the hardness, average friction coefficient and wear volume of the cladding layer reach 808 HV1, 0.183, and 8943 μm3, respectively. The reasonable addition of LaB6 significantly improves the friction and mechanical properties of the cladding layer.