Effect of TiC Addition on the High-Temperature Hardness and the Carbide Stability in Al 0.2 CoCrFeNi 1.5 Ti High-Entropy Alloy

High-entropy alloys (HEAs) are an emerging and rapidly developing family of alloys with appealing properties, such as excellent mechanical properties at room temperature and elevated temperatures. To obtain new HEAs with better high-temperature hardness than typical commercial high-speed steels, we prepared the (Al 0.2 CoCrFeNi 1.5 Ti) 100 – x (TiC) x ( x = 0, 0.05, 0.1, 0.2, 0.3) HEAs and analyzed their microstructure, room-temperature hardness, and high-temperature hardness. The HEAs demonstrated stable FCC + η + TiC phases and presented increased hardness with the addition of TiC, and the high-temperature hardness slowly decreased with elevated temperature. The x = 0.3 HEA exhibited ~590 HV at 973 K, which is higher than typical commercial high-speed steels and tungsten cemented carbide. The TiC showed good phase stability in the HEAs, and a thermodynamic model was proposed to explain and predict the phase stability of carbides in the current and other HEAs, which showed good agreement with experimental results. The (Al 0.2 CoCrFeNi 1.5 Ti) 100 – x (TiC) x HEAs can be applied as promising high-temperature tool materials, and the model may be beneficial in the design of new high-hardness HEAs with desired stable carbides.