Exceptional Wear Resistance and Unique Friction Behavior in High‐Entropy Rare‐Earth Dodecaboride Composite

ABSTRACT A high‐entropy dodecaboride composite (HEDC), i.e., (Dy 1/6 Ho 1/6 Er 1/6 Tm 1/6 Lu 1/6 Hf x )B 12 matrix reinforced by HfB 2 particles, was prepared by spark plasma sintering technique to explore its friction and wear behaviors under various conditions. The wear measurements indicate that its volume wear rates are not only far smaller than those of widely used abrasive materials, including SiO 2 , but also lower than the typical values reported recently for high‐entropy ceramics, making the HEDC the most wear‐resistant known high‐entropy conductor with metallic electrical conductivity. We demonstrate that the high‐entropy effect significantly improves the inherent wear resistance of the dodecaboride matrix, and the introduction of HfB 2 reinforcement grains suppresses the initiation and propagation of microcracks to further enhance the wear‐resisting performance. The ball‐on‐disc tests show that the average friction coefficients of the HEDC increase with rising sliding speeds and applied loads, completely opposite to the variation trend of the single‐phase high‐entropy dodecaboride. Through detailed microstructure analysis, it is found that the wear behaviors of the HEDC ceramics comply well with the characteristics of fatigue wear. This study promises to open a new avenue toward super wear‐resistant materials by forming particle‐reinforced high‐entropy composites.