On the investigation of microtructure, microhardness and tribological behavior of Ti-6Al-4V nitrided by pulse Nd-YAG Laser irradiation

Abstract The purpose of this paper is to evaluate the microhardness and characterize the microstructure of a Ti-6Al-4V alloy nitrided with a pulsed Nd-YAG laser under nitrogen gas flow. The Ti alloy surface was irradiated and melted at various laser scanning speeds. The phase analysis by X-ray diffraction for different irradiation conditions, revealed the formation of three phases: α-Ti, TiN, and TiN0.3. The results revealed that the microscopic analysis using optical and scanning electron microscopies revealed the presence of dendritic microstructure in both the laser-melted and nitreded zones, with TiN dendrites concentrated near the treated alloy's surface. Moreover, the wear of nitrided samples was examined using a pin-on-disk tribometre, the results revealed that the thickness of the TiN nitride layer (2 to 8 μm) affected the morphology of wear tracks.