Laser surface treatment of Ti-6Al-4V for bio-implant application

Abstract

The present study aims at enhancing the wear resistance of Ti-6Al-4V by laser surface melting and nitriding and subsequently, studying the influence of laser surface treatment on the corrosion resistance in a simulated body fluid and also the bio-compatibility. The laser surface treatment is carried out using a high power continuous wave diode laser with argon and nitrogen as shrouding gas. Laser surface melting leads to an increased volume fraction of acicular martensite and a decreased volume fraction of the β phase in the microstructure. Laser surface nitriding leads to the formation of titanium nitride dendrites. The micro-hardness could be improved up to a maximum of 450 Hv in laser surface melting and 900-950 Hv in the case of laser surface nitriding as compared to 260 Hv of the as-received substrate. Surface melting increases the corrosion potential (E_corr) and primary potential for pit formation (E_pp1) significantly as compared to the as-received Ti-6Al-4V. However, when processed under similar conditions, surface nitriding shifts Ecorr marginally in the more noble direction, and increased E_pp1 as compared to Ti-6Al-4V. The biocompatibility behaviour shows a superior cell viability on surface nitriding and an inferior cell viability on surface melting as compared to the as-received Ti-6Al-4V.