Microstructure, mechanical property, reciprocating sliding wear and electrochemical corrosion of AlCoCrFeNi high entropy alloy coatings with Si addition prepared by HVOF spraying

AlCoCrFeNi and AlCoCrFeNiSi high entropy alloy (HEA) coatings have been prepared by high velocity oxygen fuel spraying, and the microstructure, mechanical properties as well as wear behaviors of the two HEA coatings were studied. With Si element addition, the surface and cross-sectional microstructure of HEA coating are refined, and it was found that both HEA coatings have a body-centered cubic structure, and the X-ray diffraction peaks of AlCoCrFeNiSi HEA coating deviate to the right. The microhardness, bonding strength nanohardness and elastic modulus of AlCoCrFeNi HEA coating increased with addition of Si element due to the fact that Si promotes uniformly distribution of other elements. In terms of wear properties, coefficient of friction and the wear rate were reduced with Si element addition, and the two HEA coatings have similar wear mechanism at the same loads. And at lower loads, the wear mechanism is abrasive wear, adhesive and slight oxidative wear, it is turn to oxidative wear and severe abrasive wear while the load is increased. The AlCoCrFeNiSi HEA coating has a higher corrosion potential and a lower corrosion current density, indicating improved corrosion resistance. This enhancement is attributed to the presence of Si, which reduces interatomic spacing and results in a more compact atomic arrangement. Consequently, element migration and chemical reactions are reduced, leading to the formation of a denser and more uniform passivation film.