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 250 W and 400 W at a scan velocity of 5 mm/s, with input energy of 42 J/mm2 and 68 J/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 2.25×10−3 K/s and 1.41×10−3 K/s during LSM. Increasing the energy input increased the thickness of remelted region from 779 to 802 µm and 1173 to 1199 µm. Similarly, as a result of slow cooling rates under present experimental conditions, the grain size of the alloy increased from 4.8 μm to 154–199 μm. However, the hardness of the Ti6Al4V alloy increased due to LSM melting and resulted in lowest in vitro wear rate of 3.38×10−4 mm3/Nm compared to untreated substrate with a wear rate of 6.82×10−4 mm3/Nm.