Effect of silicon microalloying on microstructure and HVOF spraying behavior of AlCrFeCoNi high-entropy alloy coating

This study investigates the effect of 0.11 wt. % Si microalloying on AlCrFeCoNi high-entropy alloy coatings produced via mechanical alloying and HVOF spraying. Optimal milling times were 7.5 h for the base alloy and 10 h for the Si-modified one. Spark plasma sintering revealed mixed Body-Centered Cubic and Face- Centered Cubic structures with silicide precipitates. Preliminary abrasive wear tests indicated a tendency for surface stabilization in the Si-modified alloy due to tribo-oxide films. Crucially, during HVOF, Si preferentially oxidized, shielding Cr from burnout (17.64 vs. 14.16 % in the base coating) and significantly improving coating adhesion by eliminating through-cracking, forming a monolithic structure.