Microstructures and Wear Resistance of Al-25 wt.%Si Coatings Prepared by High-Efficiency Supersonic Plasma Spraying

Hypereutectic Al-Si alloy is an ideal surface strengthening material for aluminum alloy cylinder body. However, the coarse eutectic silicon phase and primary silicon particles in Al-Si alloys prepared by traditional methods lead to poor mechanical properties of the alloys, and the high cost of preparation limits the practical application of hypereutectic Al-Si alloys. In this study, Al-25 wt.%Si coatings were prepared on substrate 7075 by high-efficiency supersonic plasma spraying (HESP). The micromorphology, Vickers hardness, bonding strength and wear resistance of the coatings were measured and characterized by experiments. The results show that the Al-25 wt.%Si coatings prepared by HESP have a denser structure, and the primary silicon phase in the coatings is refined. The hardness of the coatings is 235 HV0.1, and the bonding strength between the coatings and the substrate is 44.1 MPa. The wear rate of the coatings is reduced by 20 times compared with that of the substrate, and the wear mechanism is mainly adhesion wear and oxidation wear.