Abstract: Many cases investigated so far have offered solutions to overcome high-temperature wear issue of alloys, but achieving both satisfactory mechanical and high-temperature tribological properties remains a challenge. In the present work, we fabricate a simply model Ni20Cr-based alloys with well-balanced mechanical and high-temperature tribological properties by using mechanical alloying and spark plasma sintering. We find that the alloy with 30 wt.% Co and 3 wt.% Al (NA30C) shows a room temperature compressive strength of up to 2532 MPa. The wear rate of NA30C at 600 °C and 800 °C is two orders of magnitude and seven times lower, respectively, than that of the alloy lacking Co (NA). Such exceptional performance is mainly attributed to the synergy of heterostructure, characterized by multi-level grain size, and tribo-oxidation of Co and Al with optimum content. The addition of 30 wt.% Co appropriately upgrades grain size differentiation and promotes precipitates dispersion, which saliently improves strength and plasticity of the alloy. During sliding, the formation of a protective double-layered tribo-oxide layer, consisting of a Co-rich nanocrystalline surface layer and an α-Al₂O₃ inner one, supplies sufficient lubricity, high oxidation resistance, and ideal interfacial bonding. By elucidating the mechanisms above, this study provides a new thinking for designing high-temperature self-lubricating alloys through synchronous regulation of microstructure and tribo-oxidation behavior.

Key words: Oxidation, Nanocrystalline, Wear, Spark plasma sintering, Heterogeneous structure