The effect of oxygen on the tribological behavior of CrNiMo steel

The purpose of this paper is to study the friction and wear properties of CrNiMo steel pin against brass disk in different oxygen fractions. CrNiMo steel is currently widely used in industry and military fields for its excellent performance in some severe environments. The atmosphere and temperature are key factors affecting the wear behaviors of CrNiMo steel. The study aims to make better use of CrNiMo steel in different atmospheres. Friction and wear experiments were conducted using a pin-on-disk tribometer equipped in an atmosphere controllable chamber. The chamber allows switch between vacuum and gas mixtures of N2 and O2. The oxygen content was managed by magnetic coupling flow meter. The sliding speed of 1, 2, 3, 4 m/s and the applied sliding contact load of 5, 6.5, 8, 9.5 N were used in friction test. In order to obtain information on the wear mechanisms, the worn surface of the pin was examined by scanning electron microscopy and energy dispersive X-ray spectroscopy. A close dependence is clearly shown of the friction and wear on the content of oxygen gas in elevated temperature. Increasing the content of oxygen in the atmosphere under higher normal load condition is beneficial to friction reduction of the steel/brass pair. Different wear mechanisms were found with a transition from the adhesive wear in nitrogen, to a mixed adhesion and oxidation wear when increasing the content of the oxygen in the atmosphere. This paper provides a reference for the similar steel used in severe environments.