Microstructure and tribological properties in Al–Si–Cu alloy friction-surfaced coatings processed by submerged fast multiple-rotation rolling

Al–Si–Cu alloy coatings were deposited on AA1010 aluminum by friction surfacing and post-treated using submerged fast multiple-rotation rolling (FMRR). The effect of tool rotational speed (200–1100 rpm) on microstructure and tribological behavior was systematically evaluated. Increasing rotational speed raised interface temperature from 372 to 425 °C, reduced coating thickness from 2.21 ± 0.04 to 1.61 ± 0.02 mm, and increased the thickness of the refined surface layer from 53.8 ± 1.1 to 98.3 ± 1.2 µm. Optimal refinement occurred at 800 rpm, producing fine equiaxed grains (3.74 ± 0.11 µm), uniformly distributed Al 2 Cu precipitates, and fragmented silicon particles. This condition yielded the highest nano-hardness (5.56 ± 0.12 GPa) and reduced wear rate by 52% and 79% compared to the consumable rod and AA1010 substrate, respectively.