Temperature-dependent tribological performance of HVOF-thermal sprayed FeCoCrNiAl HEA coating deposited on TC4 alloy

Abstract A FeCoCrNiAl high-entropy alloy (HEA) coating was deposited on a Ti-6Al-4V (TC4) alloy substrate by high-velocity oxygen fuel (HVOF) thermal spraying to enhance its sliding wear performance. Reciprocating sliding tests were conducted from 25 to 300 °C, and the temperature-dependent friction behavior, wear morphology, and damage evolution were examined. Meanwhile, an Archard-based finite element model incorporating the arbitrary Lagrangian–Eulerian adaptive mesh technique was established to reproduce the progressive wear process. The coating exhibited a compact lamellar microstructure, a BCC-dominated phase constitution, and higher hardness than the TC4 substrate. Although friction and wear increased with temperature for both materials, the coated specimens consistently showed lower coefficients of friction and less severe surface damage. Compared with the TC4 substrate, the HEA coating reduced the maximum wear depth and wear volume by 30.7% and 23.7%, respectively, at 25 °C, while the corresponding reductions reached 41.2% and 40.8% at 300 °C. Notably, the maximum reductions of 49.3% and 42.4%, respectively, were obtained at 200 °C, demonstrating that the protective effect of the coating became more pronounced at elevated temperatures. The wear of TC4 evolved from ploughing and plastic deformation to oxidation-assisted fatigue damage, whereas the coating mainly underwent mild abrasion, oxidation, and localized inter-splat delamination. The simulated wear profiles agreed well with the experimental results, with deviations below 5%, and revealed a reduced stress concentration in the coated specimens. These findings demonstrate that HVOF-sprayed FeCoCrNiAl coatings can effectively suppress temperature-induced wear degradation of TC4 alloy.