Investigation of the effects of grain size and nano-sized reinforcements on tribological properties of Ti6Al4V alloy

Tribological properties of nanostructured Ti6Al4V alloy in the presence of nano-sized reinforcements have been investigated. Bulk nanostructured Ti6Al4V alloy and Ti6Al4V/(Ti–B) nanocomposite were produced from milled powders by cold pressing under 400 MPa for 20 min and sintering at 1100 °C for 2 and 4 h, respectively. Hardness values of bulk nanostructured Ti6Al4V alloy and the nanocomposite were ~833 HV and 1030 HV, respectively, much higher than that of commercial Ti6Al4V plate (~450 HV). A pin on disk technique under applied load of 80 N for 600 m was used to study wear behavior of samples. Study of the worn surfaces and wear debris was done by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The commercial Ti6Al4V alloy had the highest wear rate (~13×10−2 mg/m) with lowest friction coefficient (~0.02). The nanocomposite had the lowest wear rate of ~5×10−3 mg/m and highest friction coefficient (~0.09). This improvement in the wear resistance could be assigned to higher hardness of nanocomposite due to the presence of nanoparticle reinforcements and nano-sized grains. The abrasive and adhesive wear mechanisms were responsible for wear of both commercial Ti6Al4V plate and nanostructured Ti6Al4V alloy while delamination mechanism controlled wear of the nanocomposite.