Enhanced microstructure, mechanical, and tribological properties of Al, Ti, and nano-hBN-modified CoCrFeMnNi high-entropy alloy composites at elevated temperatures

Abstract

This study investigates the microstructure, mechanical properties, and tribological performance against Si₃N₄ ball of CoCrFeMnNi high-entropy alloy (HEA) matrix composites modified with 2 wt% Al, 2 wt% Ti, and varying nano-hBN contents. Spark plasma sintering (SPS) was employed to achieve grain refinement, the formation of Cr₂B and TiN phases, and improved hardness and yield strength. The composites demonstrated exceptional wear resistance, especially at elevated temperatures. At 900 °C, a continuous oxide layer enhanced wear protection, while at room temperature (RT), the hBN lubrication film reduced wear. The 0.5 wt% hBN composite exhibited optimal performance, combining reduced wear rates, improved mechanical properties, and a consistent tribological response across a wide temperature range.