Laser cladding of TiCN/Ti coatings on Ti-6Al-4V and the calculation of the temperature field

TiCN/Ti reinforced layers were fabricated on titanium alloy by the laser cladding method, aiming at improving its surface properties. Ti and TiCN powders of size 60 and 3 µm, respectively, were mixed in a certain ratio, prepasted on a Ti-6Al-4V substrate, and irradiated with a pulsed YAG laser in nitrogen atmosphere. The temperature field was calculated with a semi-infinite model. The calculated results show that the laser scanning velocity should be in the range of 1.0 to 3.0 mm/s; the best value for metting the substrate and realizing the cladding process is about 1.4 mm/s. The cladded samples were analyzed with x-ray diffraction, optical microscope observation, and a microhardness test. The results indicate that the composition of the cladding layer changes with the ratio of Ti to TiCN. The optimum Ti:TiCN mass ratio is about 15:85. The optical micrograph revealed a TiCN film thickness about 100 µm. The hardness was increased from 330 HV in the substrate to nearly 1500 HV in the modified layers, due to the presence of the hard TiCN phase. It is found that the proper laser scanning velocity to obtain high cladding quality is about 1.5 mm/s, which agrees with the calculated result of 1.4 mm/s.