High speed sliding of Al 2O 3 pins against an En-24 steel disc

Abstract

During the high speed sliding of an 87% Al 2O 3 pin against steel, surface chemical interactions lead to the formation of a surface layer. The coefficient of friction is affected by the surface layer and under certain conditions starts to oscillate between two levels, while under other conditions it has a steady single value. The factors which decide the nature of the friction appear to be not only the speed and pressure, but also the relative contact area (the ratio of the pin surface area to the disc track area). The following empirical relation has been suggested to identify the occurrence of oscillating friction: N = S 2 P 0.75 A 0.5 where S is the speed (m s −1), P the pressure (MPa) and A the ratio of the contact area of the pin to the disc track area. For N < 19 the expected behaviour is that of R3, for 19 < N < 21 the response can be of either regions and for N > 21 R4 behaviour occurs.