Self-lubrication of high-entropy carbide matrix composites over a wide temperature range: The synergistic effect of silver and molybdenum component

High-entropy carbide ceramics are promising candidates for the structural applications in aerospace and aviation fields. However, theirs tribological properties still need to be further improved. Inspired by the toughening effect of Ag and the tribo-chemical reactions generated lubricating phases between Ag and the constituent elements of ceramics, self-lubricating high-entropy carbide composites over a wide temperature range were prepared by tailoring the contents of Ag and Mo. The results indicate the fracture toughness of H4 sample (with 10 wt% Ag and 10 wt% Mo) reaches 4.71 MPam1/2. Meanwhile, the tribological performances of high-entropy carbide composites against Al2O3 balls are effectively enhanced over a wide temperature range. Especially at 300 ◦C, the friction coefficient and wear rate of H4 are reduced to 0.46 and 1.93 × 10􀀀 7mm3/Nm, which are 58.2% and 72% lower than that of the pure (Hf0.2Mo0.2Nb0.2Ta0.2Ti0.2)C ceramic, respectively. The primary self-lubrication mechanisms are the tribo-chemical reactions generating multi-component lubricating films.