Tribolayer integrity controls the wear behaviour of FeCrNi, CoCrNi, and FeCoCrNi alloys up to 1000 °C

The design of high-temperature wear-resistant materials generally relies on mechanically dominated strategies, while the properties and integrity of tribolayers are often overlooked. Here, we decouple the mechanical properties and tribolayer integrity by assessing FeCrNi, CoCrNi, and FeCoCrNi medium-entropy alloys. Glaze layers form on all alloys at 1000°C, yet FeCrNi exhibits a wear rate five times that of CoCrNi and three times that of FeCoCrNi. High-temperature hardness of the matrices and nanoindentation hardness of the glaze layers vary modestly across the three alloys, suggesting that wear deterioration in FeCrNi is not governed solely by the mechanical properties of the matrix or glaze layer. Instead, a glaze layer rich in nanoscale intergranular voids, together with interfacial voids and a thick oxide scale, promotes the exfoliation of the protective glaze layer. Our findings provide a tribolayer-focused design criterion for high-temperature wear-resistant alloys.