High-temperature sliding wear behavior of nitrided Ni45(CoCrFe)40(AlTi)15 high-entropy alloys

Abstract

The nitrided layer on Ni 45 (CoCrFe) 40 (AlTi) 15 high-entropy alloys (HEAs) was prepared by plasma nitriding. The microstructure, hardness, the effect of temperature on the tribological properties and adhesive strength of the nitride layer were investigated. The results revealed that the as-cast alloy was composed of a single FCC phase, and the hardness measured by nano-indentation was 8.8 GPa. After nitriding, the hard phases, such as AlN, CrN, Fe 3 N, and TiN, appeared, the surface hardness was increased to 14.9 GPa, and the hardness distribution of the cross section of the nitrided layer was uniform. Moreover, the scratch test showed that the nitrided layer had good bonding properties with the substrate. The friction coefficient and the wear rate were significantly reduced, compared to the as-cast alloys due to the generation of unique nitride particles on the surface of the nitrided alloys. At low temperatures, the friction mechanism of as-cast and nitrided alloys was dominated by the adhesive wear and abrasive wear. Subsequently, the friction mechanism was changed to the oxidative wear and delamination wear with increasing the temperature. • Hard particles of AlN, CrN, Fe 4 N, and TiN phases were produced after nitriding. • The surface hardness of HEAs increased from 8.8 GPa to 14.9 GPa after nitriding. • The thickness of the nitrided layer on Ni 45 (FeCoCr) 40 (AlTi) 15 HEAs was 11.5 μm. • The wear resistance of nitrided HEAs was superior than that of as-cast HEAs. • Oxidative behavior played a dominant role in high wear resistance of HEAs.