Effect of Gas Composition on Nitriding and Wear Behavior of Nitrided Titanium Alloy Ti-15V-3Cr-3Al-3Sn

Titanium alloy, Ti-15V-3Cr-3Al-3Sn was nitrided at different temperatures with low pressure plasma with 100% nitrogen, and nitrogen diluted with hydrogen and argon. The nitrided layers were characterized for hardness, structure, and composition. Nitrided samples show weight gain that depended on temperature and duration of nitriding. EDS results show that intake of nitrogen is significant at temperatures above 750 °C. Hydrogen dilution increases intake of nitrogen. Samples nitrided with hydrogen dilution have lower surface roughness and higher nitrogen concentration. Depth profiling by XPS shows the formation of nitride in the near-surface region and also that nitrogen concentration in the interior of the nitrided layers is higher at higher temperatures. Micro Raman shows that formation of nitride takes place at higher temperatures. XRD shows that the nitrided layers consist predominantly of alpha Ti and Ti₂N. This is reflected in the hardness increase and hardness profile in the nitrided samples. The low intake of nitrogen by the alloy is attributed to the low solubility of nitrogen in beta alloy and low diffusion coefficient of nitrogen. Reciprocating wear studies showed a lower coefficient of friction and lower wear loss for nitrided samples compared to that of substrate.