Tribological insights of Co- and Ni-based alloys in extreme conditions

The purpose of this study was to investigate the friction and wear behavior of Co- and Ni-based materials under low and high temperature environmental conditions. The ultimate goal was to identify the underlying interfacial processes leading to the observed tribological behavior. Experiments were conducted using a high temperature flat-on-flat fretting apparatus with uncoated pins against a Ni-based counterface. The results showed that the coefficient of friction for this tribocouple decreased with increase in temperature. Similarly, the wear is evidently lower at elevated temperatures compared to the tests performed at lower temperatures. The emphasis of this study was placed on the correlation between the tribological behavior of the Co-based alloy and the third body formation process, characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Ex situ cross-sectional analysis by means of optical microscopy and SEM revealed the formation of transferred oxidized material on the pin. The thickness and composition of the tribofilm varied depending on the sliding condition and correlated well with the friction and wear behavior. This behavior was consistent with the observation from the XPS. •The friction and wear behavior of Co- and Ni-based materials was investigated under extreme conditions.•Ex situ characterization by means of SEM and XPS revealed importance of third bodies.•Coefficient of friction for this tribocouple decreased with increase in temperature due to oxide-based tribofilm formation.