Laser cladding of the Ti 3 Al+TiB 2 pre-placed alloy powder on the Ti-6Al-4V alloy in nitrogen protective atmosphere can form the Ti 3 Al+TiB 2 /TiN composite coating, which can dramatically improve the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti 3 Al+TiB 2 /TiN composite coatings on the Ti-6Al-4V alloy have been researched by means of X-ray diffraction, SEM and energy dispersive spectrometry. It was found that there is a metallurgical combination between the Ti 3 Al+TiB 2 /TiN composite coating and the substrate. The microhardness of the Ti 3 Al+TiB 2 /TiN composite coatings were 3~4 times higher than that of the Ti-6Al-4V alloy because of the actions of the Ti 3 Al+TiB 2 /TiN hard phases and the grain refinement strengthening. Moreover, the wear mass losses of the Ti 3 Al+TiB 2 /TiN composite coatings were much lower than that of the substrate.

Laser cladding of the Al3Ti+TiC+(Ni-coated WC) pre-placed powders on titanium alloy can form the Ti3Al/Al3Ti matrix composite coating, which improves the surface performance of the substrate. With addition of nano-Y2O3, this composite coating exhibited a finer microstructure. In this study, the Al3Ti+TiC+(Ni-coated WC)+nano-Y2O3 laser-cladded coatings have been researched by means of X-ray diffraction and scanning electron microscope. The function of nano-Y2O3 acted as the heterogeneous nuclei, and the growth of the grains was hindered by Y2O3 and Y. Y2O3 can also decrease the temperature of the molten pool. Thus, the probability that grains traverse potential barrier decreased, leads to more stability of the grains.K e y w o r d s : coatings, rare earth compounds, laser cladding, intermetallics, diffusion