Exploring ambient and elevated temperature fretting wear behavior of laser-cladding (FeCrCoNi)84AlxNby high-entropy alloy coatings

In this work, (FeCrCoNi)84AlxNby (x = 12, 8, 4 and y = 4, 8, 12 (at. %)) high-entropy alloy (HEA) coatings were successfully deposited on 316 stainless steel via laser cladding (LC). FCC/BCC + Laves structure was introduced into FeCrCoNi HEA system by designing different Al/Nb ratios, aiming to improve the fretting wear resistance. The phase constituents, microstructure, and fretting wear resistance of (FeCrCoNi)84AlxNby HEA coatings at ambient temperature and 285 °C were respectively analyzed. Results confirmed that the microstructure of three HEA coatings displayed the interdendritic (IR) - dendritic (DR) structure. With the Al/Nb ratio decreased from 3/1 to 1/3, the phase constituents of HEA coatings transformed from the BCC solution to FCC solution and Laves phase, and the content of the Laves phase gradually increased. Moreover, the average grain size decreased from 16.9 μm to 4.6 μm, while the average geometrically necessary dislocations (GNDs) density increased from 1.842 × 1010 m−2 to 2.821 × 1010 m−2. The microhardness of the HEA coatings was improved from 210 HV0.2 to 361–647 HV0.2 compared with that of the substrate. The decrement of Al/Nb ratio improved the fretting wear resistance of HEA coatings both at ambient temperature and 285 °C, especially at 285 °C. The wear volume decreased from 0.8 × 105 μm3 to 0.39 × 105 μm3 and the fretting wear mechanism changed from severe fatigue wear to slight abrasive wear at 285 °C. In the Al4Nb12 HEA coating, the soft structure (FCC) and the hard structure (Laves) were combined into a wear-resistant skeleton, and the Laves structure was massively distributed along the FCC phase to prevent the FCC phase from further slipping in the fretting wear process, which in turn minimizes the fretting damage. The present work provides a theoretical basis for the related research on the fretting wear characteristics of laser cladding HEA coatings. •The (FeCrCoNi)84AlxNby high-entropy alloy coatings are successfully fabricated via laser cladding technology.•The change of Al/Nb ratio has a great impact on the microstructure and elevated temperature fretting wear resistance.•The fretting wear volume is reduced about 4.05 times at 285 °C.•The synergistic effect of the FCC structure and Laves structure results in excellent fretting wear resistance.