In-situ synthesis of TiC/Ti alloyed layer via pulsed Nd:YAG laser melting of Ti-6Al-4V titanium with preplaced carbon-based powder

Abstract

The present research deals with fabricating an in-situ TiC/Ti alloyed layer on the Ti-6Al-4V titanium alloy through the preplacement of a mixture of graphite and nickel powders and subsequent pulsed Nd:YAG laser melting. The comprehensive effects of laser parameters, including scanning speed and energy density on the microstructural evolutions and hardness variations were investigated. It was found that the geometry of treated layers varied from 150 to 200 µm in thickness and 1200–1750 µm in width depending on the thickness of the preplaced layer and laser peak power. The promising results of X-ray diffraction patterns and scanning electron microscope observations manifested the formation of in-situ TiC and an increase in its content versus the energy density of the laser beam. The main mechanism of the in-situ formation of TiC in the matrix during laser irradiation was also discussed. The results indicated that the in-situ TiC phases had either dendritic or needle-like morphology. Laser parameters were crucial in establishing the TiC morphologies associated with temperature and chemical composition. The hardness values of the fabricated layers were directly proportional to the amount of TiC in the treated layers and varied from 1000 to 1400 HV0.3, which was nearly 3–4 times higher than that of the substrate.