Tribological behavior of boronized Al0.1CoCrFeNi high-entropy alloys under dry and lubricated conditions

High-entropy alloys (HEAs) with a single-phase face-centered cubic (FCC) structure generally have excellent plasticity. However, its limited room temperature strength and hardness result in lower wear resistance, which hinders tribological and engineering applications. In this paper, the pack-boronizing method was used to improve the tribological properties of Al0·1CoCrFeNi HEAs with a single-phase FCC structure. The boronizing treatment was carried out at 900 °C for 2, 4, 6, and 8 h, respectively. The structure and phase formation of boronized alloys were studied. Moreover, the reciprocating sliding wear behavior of boronized alloys against Si3N4 balls in dry and deionized water was investigated. A boronized layer with a double-layer structure was formed on the HEA surface, with a total thickness of about 17.3–58.5 μm. The wear mechanism of boronized alloy was transformed from the abrasive and delamination wear to the polishing effect with increasing the boronizing time in air. In contrast, the wear mechanism of boronized alloys in the deionized water gradually changed from the two-body to three-body wear with increasing the boronizing time. Meanwhile, the wear mechanism of the Si3N4 counterface was also transformed to three-body wear gradually. •The maximum hardness of boronized HEAs is higher 7 times than that of annealed HEAs.•The wear rate of boronized HEAs was much lower than that of as-cast HEAs.•The wear mechanism of boronized HEAs in air was abrasive wear and polishing effect.•Wear mechanism of HEAs in deionized water was two-body and three-body abrasive wear.•The lubrication of deionized water led to lower friction coefficient and wear rate.