Tribological Behaviors and Typical Wear Mechanisms of Nearly Single FCC Phase AlCoCrFeNi High-Entropy Alloy at Ambient Temperature

The friction and wear properties and behaviors of nearly single face-centered cubic (FCC) phase AlCoCrFeNi high-entropy alloy and its shot-blasting samples at ambient temperature were investigated in detail by SRV-IV micro-vibration friction and wear testing machine. The variation in the wear of the AlCoCrFeNi high-entropy alloy showed a positive correlation with both friction frequency and normal load. With the increase of friction frequency (6~40 Hz), the atomic arrangement of the friction interface of the high-entropy alloy gradually changed from mainly along (100) crystal plane to along (111) plane, showing a significant preferred orientation, and the main wear mechanism of the high-entropy alloy gradually varied from oxidative and delamination wear to plastic deformation and delamination wear. Raman spectrum analysis showed that complex oxides exist in the wear tracks formed at all the tested friction frequencies except 30 Hz, and their crystalline structures were similar to Al₂O₃ and Cr₂O₃. With the increase of normal load (10~200 N), the crystalline grains at the friction interface of the alloy became finer, and the atomic arrangement of the friction interface tended to be along (111) plane. The dominant wear mechanism of the alloy changed from oxidative wear to fatigue wear, and finally to adhesive wear. Due to the strengthening effect of fine grains, the surface micro-hardness of the AlCoCrFeNi high-entropy alloy after shot blasting was up to 403 HV, which was nearly twice as high as that before shot blasting. The surface strengthening layer formed by shot blasting treatment would reduce the wear of the alloy, and its thickness was about 25 μm. With the increase of friction time, the primary wear mechanism of the high-entropy alloy shot-blasting specimens gradually changed from plastic deformation and delamination wear to simultaneous oxidative wear (in some extent); the combination of plastic deformation and delamination wear mechanism would lead to the fantastic zero wear behavior of the alloy shot-blasting sample. The nearly single FCC phase AlCoCrFeNi high-entropy alloy and its shot-blasting samples revealed various and typical wear behaviors and mechanisms for special element composition and atomic arrangement. In this study, several typical wear mechanisms of the high-entropy alloy at ambient temperature were clarified, and the actual impact of shot blasting on it was evaluated. This work provides important basis for the rational application of the high-entropy alloy system and the composite structure high-entropy alloys containing FCC phase in the field of wear protection and in-depth understanding of their service behaviors.