A (CrFeNi)83(AlTi)17 high-entropy alloy matrix solid-lubricating composite with exceptional tribological properties over a wide temperature range

High-entropy alloy matrix solid-lubricating composites (HSLCs) are promising anti-wear and friction -reduced materials to meet the demands of complicated engineering applications. Here we present a strat-egy to develop HSLCs by using the coupled high-entropy phases of (BCC + FCC + L2 1 ) with near-equal volume fraction as the matrix material, instead of using the usual single phase-dominated high-entropy phases, which can preserve the intrinsic strength and deformability of the matrix while activating adap-tive wear protection during sliding. This enables a low coefficient of frictions of 0.23-0.31 and wear rates within the order of 10 -6 -10 -5 mm3 N m -1 for the (CrFeNi)83(AlTi)17-Ag-BaF2/CaF2 HSLC between room -temperature and 800 degrees C, considerably outperforming the reported HSLCs and conventional alloy matrix solid-lubricating composites. At low and moderate temperatures, the synergistic Ag-BaF2/CaF2 lubricat-ing films eliminate the surface stress concentration upon wear, thus suppressing three-body abrasion and surface roughening during the groove multiplication process. At elevated temperatures, the high-entropy composite tribo-layers provide the friction interface with strong and deformable stress shielding, which avoids the oxidative and adhesive wear triggered by the delamination of the tribo-layer. Developing sim-ilar coupled high-entropy matrix phases may open an avenue for further optimization of the tribological properties of the HSLCs. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.