NiTi coating on Ti-6Al-4V alloy by TIG cladding process for improvement of wear resistance: Microstructure evolution and mechanical performances

A thick layer of NiXTiY (NiTi and NiTi2) was deposited on Ti-6Al-4V alloy by tungsten inert gas (TIG) cladding process using Ni and Ti powder mixture prepared by ball milling route as precursor. The analysis shows that the microstructure of the produced NiTi coating principally governs by the heat input, which was controlled through the employed processing current. The hardness of the NiTi clad layer measured by Vickers micro-indentation method was found reasonably higher as compared to Ti-6Al-4V alloy substrate. The XRD and EDS analysis of the clad layer revealed the formation of NiTi and NiTi2 as major phases along with some unreacted Ti and TiAl3 intermetallic. The sliding abrasive wear of the coating performed against abrasive disc shows upto 9.5 times reduction in the wear value as compared to the uncoated Ti-6Al-4V alloy as measured by its height loss. The experimental results revealed an ample effect of the TIG current on the hardness value and wear characteristic of the clad layer, which is predominantly dependent on the morphology and percentage of phase constituent formed. The produced NiTi coating has prospective applications in biomedical, where inadequate wear resistance of Ti-6Al-4V alloy is the major concern for its use.