High‐temperature self‐lubricating properties of single‐phase high‐entropy carbides under a vacuum environment.

It is an enormous challenge to develop single‐phase ceramics with satisfactory self‐lubricity because of the strong chemical bonding and difficult to shearing. In this study, (Hf0.2X0.2Nb0.2Ta0.2Ti0.2)C (X is Zr, W, and V, respectively) single‐phase high‐entropy ceramics can in situ formed tribo‐film on the contact region during sliding process to achieve an excellent self‐lubricating property. The friction coefficient is as low as 0.34 at 400°C. This originates from the carbon‐rich tribo‐films which are generated under the effect of high‐temperature tribo‐induced. With the test temperature increasing, the wear mechanism changes from abrasive wear to oxidative wear. For the 900°C, the tribo‐oxidative film limits the direct contact between tribo‐couple and enhances the tribological performances. Moreover, the compositions of the tribo‐films also have an important effect on the tribological behaviors. This novel design concept—using own constituent elements to generate a lubricating tribo‐film will provide a new strategy for the study of the single‐phase self‐lubricating ceramics. [ABSTRACT FROM AUTHOR]