Simultaneous improvement in the hardness and friction characteristics of Ti-6Al-4V through laser cladding with nanoscale SiC particles in an air environment

Abstract

Laser cladding with SiC nanoparticles was performed on a Ti-6Al-4V substrate in an air environment. In this process, the oxide and reinforcement phases formed together in the coating layer and, consequently, the hardness and friction characteristics of the titanium surface were improved simultaneously. Specifically, the oxide phases such as SiO2 and TiO2 were formed on the top region of the coating layer through a reaction with oxygen. The reinforcement phases such as TiC and Ti5Si3, a eutectic structure, and martensite occurred in the lower region of the coating below the oxide phases. The reinforcement phases helped increase the hardness of the titanium surface by up to three times. Moreover, due to the influence of the oxide phases, the friction coefficient was reduced by up to 88% after the laser cladding. When the laser scanning speed decreased, the cooling rate decreased; therefore, the crystal size increased, and hardness value decreased. In addition, the friction coefficient decreased as the laser scanning speed decreased due to the increase in the TiO2 content and decrease in the agglomerated SiO2 at low laser scanning speeds. The amount of wear of the specimen reduced considerably after the laser cladding, and only light abrasive wear and fatigue wear were observed on the laser clad surface.