In-situ synthesized age-hardenable high-entropy composites with superior wear resistance

This work reports a new approach to in-situ synthesize high-entropy composite (HEC) with high age-hardening ability and superior wear resistance. The as-cast FeNiCrMoTiC composite consists of a face-centred cubic (FCC) solid solution matrix with in-situ formed randomly-distributed carbides and FCC/intermetallics eutectic structures. Aging at 800 °C for 96 h effectively increases the hardness and compressive yield strength of the composite due to the precipitation strengthening of intermetallics. The peak-aged composite thus shows significantly enhanced wear resistance, even higher than the high-chromium cast iron (HCCI) with much higher hardness. In contrast to the severe delamination in the HCCI, the peak-aged HEC shows moderate abrasive wear and minor delamination under sliding friction due to its unique microstructure. The in-situ formed carbides, eutectic structures and precipitates effectively hardens the soft FCC matrix of the HEC and thus decreases the material loss caused by abrasive wear. The relatively lower cracking susceptibility of the finer reinforced particles in HEC can also prevent severe brittle delamination. In addition, propagation of micro-cracks from the brittle particles is inhibited by the ductile FCC matrix, which suppresses the delamination behaviour. During the wear test, the spalled carbides or intermetallics were welded onto the surface of the FCC phase, which further strengthened the matrix and thus decreased the abrasive wear. The developed composite also exhibited superior oxidation and corrosion resistance, indicating a strong application potential in extreme environments associated with abrasion, corrosion and oxidation.