The role of MoS 2 in hard overlay coatings of Al 2O 3 in dry sliding

Abstract

The role of MoS 2 in Al 2O 3 ceramic coatings in dry sliding was examined experimentally. The result indicates that the tribological behaviour of pure Al 2O 3 ceramic coating is inconsistent. It is shown here that a reduction in wear volume of 2–9 times in magnitude is achieved when Al 2O 3 is codeposited with MoS 2 in different ratios. The optimum percentage by weight of MoS 2 to be codeposited with Al 2O 3 was found to be 40%. Increases or decreases in this percentage increase the wear volume, but the coating is still tribologically superior to pure Al 2O 3 coatings. The rupture and removal of this codeposited coating, unlike pure Al 2O 3 coatings, does not show any sign of catastrophic increase in wear volume. The rupture of codeposited Al 2O 3-MoS 2 coatings is found to be very slow and is followed by the formation of a black coloured solid lubricant film on the contact surface.