High-Speed Dry Tribological Behaviors of CrNiMo Steel in Nitrogen and Oxygen Atmospheres

Abstract

Abstract: In this article, the high-speed dry sliding tribological behaviors of CrNiMo steel against brass in nitrogen and oxygen atmospheres are investigated using a pin-on-disc tribometer. The worn surface is characterized by scanning electron microscopy and electron dispersion spectrums analysis. The wear mechanisms of CrNiMo steel are also analyzed. The results indicate that the tribological properties of CrNiMo steel are coincidental with the law of dry sliding of metal, where the friction coefficients decreases with an increase in sliding speed and with normal load. However, the atmosphere has obvious effects on the tribological properties of CrNiMo steel. In the sliding process, friction heat plays an important role on the tribological properties of materials in high-speed dry friction. The high-speed wear mechanism of CrNiMo steel varies at different atmospheres. In a nitrogen atmosphere, the wear mechanism of CrNiMo steel is mainly characterized by adhesion at a lower speed and load. When the speed and load are increased, melting trace is found in the worn surface accompanied by an abrasive wear. In an oxygen atmosphere, the mechanism is characterized by adhesion at a lower speed and load; with an increase in speed and load, it gradually transformed into oxidation wear and abrasive wear. The difference of the wear mechanisms in the different atmospheres and test parameters is primarily due to the transfer films formed on the contact surfaces of the sliding pairs. In our experimental conditions, the surface film is mainly the metal film in nitrogen, whereas, it is the oxide film in oxygen.