Effect of normal load on tribological properties of Ni60/h-BN self-lubricating anti-wear composite coating on Ti6Al4V alloy by laser cladding

To enhance the tribological properties of Ti6Al4V alloy, self-lubricating anti-wear composite coating reinforced with hard TiC, TiB₂, CrB and self-lubricating h-BN were fabricated by laser cladding. The phase compositions and micro structures were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), respectively. Sliding wear tests of the composite coating and substrate were conducted at 2, 5 and 8 N, respectively, with the Si₃N₄ceramic ball as the counter-body, and the corresponding wear mechanisms are discussed. Results indicate that the mean microhardness of the composite coating (HV_0.21013.75) was about 2 times higher than that of substrate (HV_0.2360). In all normal loads, both friction coefficient and wear rate of the composite coating were lower than that of the substrate. With the increasing of normal load, both friction coefficient and wear rate of the composite coating decreased firstly and then increased. It is demonstrated that the tribological properties of the composite coating showed the best at 5 N.