Microstructure, microhardness, and tribological behavior of Ti-6Al-4 V nitrided by laser irradiation

The aim of this article is to determine the microhardness, the tribological behavior, and the microstructure of a Ti-6Al-4 V alloy nitrided with a pulsed Nd-YAG (neodymium-doped yttrium aluminum garnet) laser under nitrogen gas flow. The Ti alloy’s surface was irradiated and melted at different laser scanning speeds. X-ray diffraction revealed three phases: α-Ti, TiN, and TiN_0.3. Optical and scanning electron microscopy results revealed dendritic microstructure in both laser-melted and nitrided zones with TiN dendrites concentrated near the alloy’s surface. Furthermore, surface’s wear examination using pin-on-disk tribometer revealed that the wear morphology depends on the thickness of the TiN nitrided layer (2–8 μm); thus, the enhanced wear resistance is observed in the case of the sample with thicker TiN layer obtained under a laser beam speed of 2.5 mm/s.