A heat-resistant NiCo_0.6Fe_0.2Cr_1.5SiAlTi_0.2 overlay coating for high-temperature applications

This paper proposes an overlay coating based on the high-entropy alloy composition NiCo_0.6Fe_0.2Cr_1.5SiAlTi_0.2 [high-entropy alloy coating (HEAC)]. HEAC samples underwent spark-plasma sintering processes and were subjected to oxidation tests, high-temperature hardness tests, and thermal conductivity and thermal expansion measurements. Experimental results indicated that the HEAC can form protective α-Al₂O₃ at 1100°C and exhibits oxidation behavior similar to that of MCrAlY. Furthermore, compared to MCrAlY, the HEAC possesses better thermal stability, higher hot hardness, lower thermal conductivity, and smaller thermal expansion. The potential of the HEAC as an overlay coating for high-temperature applications is discussed.