Tribological characteristics of chromium steels in three various atmospheres under high-speed conditions

Friction heat induced by high sliding speed affects tribologial properties. Tribological behaviours of chromium steels were investigated using a pin-on-disc tribometer in various atmospheres (O2, N2 and CO2). The tests had performed at sliding speeds from 30 to 60 m/s and a contact pressure of 1.33 MPa. The results show that the wear rate of the steel pin is the lowest in an oxygen atmosphere and highest in a nitrogen atmosphere. It was found that the thin and compact oxidation layer formed on the worn surface of the steel in an oxygen atmosphere plays a key role in the wear resistance. In contrast, there is free of oxides in a nitrogen atmosphere, adhesion is higher than in environments of oxygen and carbon dioxide, and there is a thick and loose surface layer formed on the worn surface of the steel. At the same time, the difference of the surface temperature due to high-speed changes the microstructure of the surface layer and causes the different tribological characteristics in the three atmospheres.