Evaluation of Nitride Layer on Ti-6Al-4V Titanium Alloy by Tungsten Inert Gas (TIG) Nitriding Method

Abstract

In order to improve the micro-hardness and wear resistance, nitride layer has been formed on Ti-6Al-4V alloy by using trailing nitrogen gas by TIG (Tungsten inert gas) melting process. Effect of nitrogen gas flow on the formation of nitride layer and its mechanical properties like micro-hardness and wear resistance have been investigated. Depending on the energy density and the amount of nitrogen gas, Titanium nitrides, Titanium-Aluminium-Nitride and their intermetallic compound are formed on Ti-6Al-4V alloy, which resulted in improvement the surface hardness and wear resistance of Ti-6Al-4V alloy. Vicker’s micro-hardness tester was used to measure the micro-hardness at the cross section of the nitride zone. Hardness of nitride zone is found two to three times higher than the hardness of titanium alloy. Wear test results revealed that the wear resistance of Titanium nitride layer is up to ten times more than the Ti–6Al–4V substrate. Also effect of TIG welding current and scan velocity on the nitrided layer and corresponding microstructure has been investigated.