Tribo-oxidation-mediated wear resistance in high-entropy metallic glass coatings

Two Fe-Ni-Cr-Mo-Nb-B-Si high-entropy metallic glass coatings, denoted Fe35 and Fe25, were fabricated by high-velocity air-fuel spraying, and their microstructures and tribological behavior under reciprocating dry sliding against a Si 3 N 4 ball were investigated. Increasing the Ni content from 10 to 20 at.% increased the amorphous fraction from approximately 75.1% to 82%. Although Fe25 exhibited slightly lower hardness, it showed lower wear rates than Fe35 at 15 and 20 N, a lower energy wear coefficient at higher loads, and a more continuous oxygen-rich tribolayer. FIB–TEM revealed that the tribolayer above the amorphous region was about 80 nm thick and clearly stratified, whereas that above the crystallized region was about 30 nm thick. Representative density functional theory calculations showed more favorable O 2 adsorption on the amorphous model than on the crystalline model. Pronounced dislocation activity in FCC regions also provided local plastic accommodation during sliding. Under the present room-temperature dry-sliding conditions, these results indicate that the microstructural heterogeneity of Fe25 is associated with more favorable initial O 2 adsorption, the formation and retention of a thicker oxygen-rich tribolayer, and enhanced local plastic accommodation in FCC regions, thereby reducing material removal at higher loads.