Microstructure, mechanical and wear properties of laser surface melted Ti6Al4V alloy.

Laser surface melting (LSM) of Ti6Al4V alloy was carried out with an aim to improve properties such as microstructure and wear for implant applications. The alloy substrate was melted at 250W and 400W at a scan velocity of 5mm/s, with input energy of 42J/mm2 and 68J/mm2, respectively. The results showed that equiaxed α+β microstructure of the substrate changes to mixture of acicular α in β matrix after LSM due to high cooling rates in the range of 2.25×10−3K/s and 1.41×10−3K/s during LSM. Increasing the energy input increased the thickness of remelted region from 779 to 802µm and 1173 to 1199µm. Similarly, as a result of slow cooling rates under present experimental conditions, the grain size of the alloy increased from 4.8μm to 154–199μm. However, the hardness of the Ti6Al4V alloy increased due to LSM melting and resulted in lowest in vitro wear rate of 3.38×10−4mm3/Nm compared to untreated substrate with a wear rate of 6.82×10−4mm3/Nm.