In-situ Forming Composite Coating by Laser Cladding C/B4C

B4C and graphite(C) mixed powders were clad by laser at the surface of Ti–6Al–4V alloy in N2 environment. X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray energy dispersive spectroscopy (EDS) were used to analyze the composite coatings. It was found that TiC, TiB, TiN, and TiB2 which were comprised of the coating were hard strengthening phases in-stiu formed. The microstructure of the coating were mainly dendrites and whiskers-like crstals in white light area. When the mass ratio of graphite is up to 40%, the micro-hardness of coating in specimen A was up to 1245 HV0.2, which was much greater than that of the substrate. The hardness of Ti–6Al–4V alloy was only 360 HV0.2. The micro-hardness of the coating in specimen B was from 1060 HV0.2 to 1358 HV0.2. The hardness of specimen B was about three to four times greater than that of the substrate. However, the residual graphite in the coating acted as a lubricant, which increased the wear resistant property of the laser cladding coating. The wear resistant property of specimen B was 4 times as great as that of the substrate. It was twice as great as that of specimen A.