Influence of the gas environment on the transferred film of the brass (Cu64Zn36)/steel AISI 1045 couple

This paper reports on the influence of environment gas on the brass film and tribological behaviour of brass (Cu64Zn34)/steel (AISI 1045) couple. The friction coefficient and the wear rate of brass/steel were measured in ambient air, in pure oxygen at 105 Pa and in vacuum at 5 × 10−5 Pa. In this study, the mechanism of brass film transfer onto steel substrate has been studied with the scanning electronic microscope, the optical microscope and the interferential microscope. The analysis shows that the transfer film properties (roughness, hardness, thickness) depend on the atmospheric conditions. The brass film has an ellipsoidal surface in air and in oxygen with two different thicknesses. However, in vacuum, the transfer film is produced by discontinuous adhered particles on the disc. The largest wear rate is obtained, when using pure oxygen and the largest friction coefficient μ was measured in ambient air. The smallest friction coefficient and wear rate are obtained in vacuum due to the transition of a brass/steel contact to a brass/brass contact after nucleation of transfer particles.