Formation mechanism and high-temperature self-lubricating behavior of (HfMoNbTaTi)C system single-phase high-entropy ceramics

• Published in: Journal of the European Ceramic Society 2023-09, Vol.43 (12), p.5099-5107
• Main Authors: Chen, Wenbang, Zhu, Zongxiao, Zheng, Min, Sun, Qichun, Zhu, Shengyu, Cheng, Jun, Yang, Jun, Liu, Weimin
• Format: Article
• Language: English
• Subjects: Elevated temperature; High-entropy carbide; Self-lubrication mechanisms; Single-phase ceramic
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2023.04.015

It is a substantial challenge to obtain single-phase ceramics with self-lubricating properties. Most conventional lubricated ceramics benefit from the addition of solid lubricants, which largely deteriorate theirs mechanical properties. Here, we report a single-phase (HfMoNbTaTi)C system high-entropy ceramic with self-lubricity inspired by the novel high-entropy design concept and regulation of high-temperature lubrication components (with different Mo contents). The formation mechanism of the single-phase structure is ascribed to the increasing of carbon vacancies with the increasing of Mo content. Meanwhile, the tribological performances are greatly enhanced at high temperature. Especially for (Hf0.149Mo0.404Nb0.149Ta0.149Ti0.149)C0.745 ceramic (with 20 wt% Mo) against Al2O3 ball at 900 °C, the average friction coefficient is as low as 0.6, and its wear rate is reduced an order of magnitude. The results show that the self-lubrication mechanisms are tribo-chemical reactions to generate lubricating tribo-films. •Single-phase (Hf-Mo-Nb-Ta-Ti)C system ceramic with self-lubricity was prepared.•The formation mechanism of the single-phase structure was investigated.•Regulation of Mo content has a significant effect on tribological properties.•Tribo-films with lubricity have a vital impact on friction reduction and anti-wear.