Surface Nitriding and Improvement of Wear Resistance of Titanium Using Laser Irradiation

Pure titanium is a biocompatible material that is also useful in high-temperature environments, however, wear resistance of the pure titanium is weak. To improve the wear resistance of pure titanium, surface modification is performed using laser beam heating under various laser conditions. The modified surface layer produced by laser melting consists of titanium nitride (TiN), which improves the hardness and the wear resistance. However, the surface of this modified layer is not flat. In this study, the laser irradiation was performed in a controlled atmosphere and the effects of the atmosphere on the microstructure, hardness, and wear resistance of the irradiated region were investigated. As the pure titanium surface was heated by laser irradiation, a TiN film was formed on its surface without the introduction of cracks. A lamellar structure was also observed under the TiN film. The maximum TiN thickness obtained without cracking or peeling of the base metal was approximately 13 pm. In comparison with the base metal, the hardness and wear resistance of the TiN film were approximately 8 and 22 times higher, respectively.