Effects of Nb additions on the microstructure and tribological properties of Al0.25CrFeNi1.75 high-entropy alloy

The microstructure evolution and tribological properties of the Al0.25CrFeNi1.75Nbx (x is molar ratio, x = 0, 0.3, 0.6, 0.66, 0.69, 0.72 and 0.75, denoted by Nb0.3, Nb0.6, Nb0.66, Nb0.69, Nb0.72, and Nb0.75, respectively) high entropy alloys (HEAs) were investigated. The results indicated that the microstructure of Al0.25CrFeNi1.75Nbx was composed of orthogonal structure phase of AlCrNi type, Laves phase of FeCrNb type and tetragonal structure phase of AlNi3 type. These alloys shows superior hardness and promising wear resistance. When Nb (the molar ratio of Nb is 0.66) were introduced into Al0.25CrFeNi1.75 alloy, the alloy showed a low wear rate which was 4.2 ± 0.40 × 10−4 mm3 N−1 m−1, and the hardness reaches 727 HV. The research finding of hardness and tribological properties demonstrated that the addition of Nb can effectively improve the hardness and wear resistance of the Al0.25CrFeNi1.75 alloy. •The microstructure and tribological properties of the Al0.25CrFeNi1.75Nbx alloys were investigated.•With the increase of Nb content to 0.6–0.72, the alloy containing three major phases: orthogonal structure phase (AlCrNi type), tetragonal phase (AlNi3 type) and Laves phase (FeCrNb type).•The average size of the coarse block phase is gradually refined with the increase of Nb content in Al0.25CrFeNi1.75 alloys.•When Nb (the molar ratio of Nb is 0.66) were introduced into Al0.25CrFeNi1.75 alloy, this alloy exhibited a low friction coefficient and wear rate, which was 0.62 and 4.2 × 10−4 mm3 N−1 m−1, and the hardness of the Nb0.66 alloy reach to 727 HV.