Titanium and its alloy Ti6Al4V have gained attention as advanced biomaterials in healthcare due to the presence of native amorphous titanium oxide layer on their surface. This inherent amorphous layer with thickness restricted to 3-7 nm imparts improve biocompatibility and corrosion resistance to the material. However, this limited thickness constrains its functional performance. This work is aimed at improving the functionality of Ti6Al4V by creating an oxide layer of suitable thickness on its surface through controlled heat treatment. Samples were oxidized at three different temperatures, 400 ºC, 600 ºC and 800 ºC for 1h and alteration in morphology, oxygen content, crystallization of oxide layer, surface energy, surface roughness and micro-harness of the samples were investigated. The electrochemical analysis revealed a systematic lowering in corrosion rate with increasing temperature. Notably, the corrosion rate of the sample heated at 800 ºC was 0.52 mil/y that is 1/4th times lower to pristine sample (2.04 mil/y). Tribology analysis showed a significant enhancement in wear resistance. The wear rate of pristine Ti6Al4V (7.56 x 10-3 mm3/Nm) reduced by two-orders for sample heat treated at 800 ºC (9.59 x 10-5 mm3/Nm) when tested against a stainless steel counterpart. Further, samples subjected to higher thermal oxidation exhibited superior bioactivity, as evidenced by increased apatite growth and calcium to phosphorus ratio closer to optimum value reported in litrature. The improved performance of thermally oxidized sample is attributed to an increase in rutile phase of crystalline titanium oxide on Ti6Al4V surface post heat treatment.
Kedia et al. (Thu,) studied this question.