Tribological Performance and In Situ-Generated Oxidative Layer of Cobalt-Based Alloy From 25 °C to 800 °C

The friction and wear performances of Haynes 25 alloy sliding against Si3N4 in a ball-on-disk configuration are investigated from room temperature (RT) to 800 °C. The friction-induced changes of morphology and chemical composition in the surface and subsurface regions of the wear tracks were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The results show that the friction coefficient (COF) decreases considerably via temperature, while the wear-rate increases and then decreases with temperature. During dry-sliding contact, the spontaneous formation of multiple metal oxides on the rubbing surface varies as a function of the test temperature, being responsible for either wear loss and/or a change of friction coefficient. The results of this study indicate that the presence of the glazed surface of Haynes 25 helps to lower friction. At 800 °C, a glaze layer with a multilayer structure appears on the rubbing surfaces, leading to the lowest friction coefficient and wear-rate.