Microstructure and cavitation erosion characteristics of Al-Si alloy coating prepared by electrospark deposition

With a high-power electrospark deposition (ESD) processing unit, an Al-Si coating was prepared on ZL101 aluminum alloy substrate. The Al-Si coating was composed of many thin deposited layers with the thickness of 30-40 μm and showed peculiar microstructural characteristics. The eutectic Si phase, which was homogenously distributed in the coating, existed in the form of latticed morphology with characteristics of being composed of many fine (~ 50 nm size) spherical Si particles. Hardness tests showed that the microhardness of the coating was in the range of 100-110 HV with a small fluctuation, which implied that the deposited coating possess a uniform strength through the whole coating. After 4 hours' cavitation erosion tests, the cumulative volume loss of Al-Si coating (9.03 mm³) was only 31.5% of the substrate (28.66 mm³), which indicated that the Al-Si coating possessed better cavitation erosion resistance than ZL101 substrate. The excellent performance of Al-Si coating was mainly attributed to the peculiar microstructure and the formation of fine spherical Si particles.