Friction behavior of alumina/molybdenum composites and formation of MoO3−x phase at 400 °C

Self-lubricating Al2O3+1-10 vol% Mo composites were synthesized by pulsed electric current sintering. Molybdenum was found to strongly influence the coefficient of friction against alumina. Lubricious oxide of Mo4O11 formed within the wear track during wear at 400 °C and reduced the coefficient of friction. The composites with Mo had coefficient of friction of 0.35-0.71 at 25 °C and 0.27-0.36 at 400 °C. No measureable wear was observed for composites with 1, 2.5 and 5 vol% Mo. Nanoscratch tests were performed inside the wear tracks to study the friction properties of the transfer film. Alumina molybdenum composites performed as wear resistant materials with very good friction properties at 400 °C owing formation of Mo4O11 during wear.