Al-20Si/Cu-8P high‑silicon aluminum alloy coating enhanced by laser remelting and refinement: Microstructure, mechanical properties and wear resistance

Abstract

An Al-20Si/Cu-8P high‑silicon aluminum alloy coating was prepared on A356 aluminum alloy by plasma spraying and was remelted by laser technology subsequently. Whereupon, the microstructure, mechanical properties and wear resistance of the coating before and after remelting were comparatively studied, aiming to investigated the combined enhancement effect of remelting and refining on high‑silicon aluminum alloy coatings. The results showed that the laser remelting basically eliminated the defects in the sprayed coating, and produced a metallurgical bonding interface between the coating and the substrate. The microstructure of the coatings before and after remelting was both composed of primary silicon and eutectic structure (α-Al + Si). Nevertheless, the Cu8P dissolved more fully and dispersed more evenly in the remelted coating, which was conducive to fully utilizing its refinement effect on primary silicon. Thus, the primary silicon in the remelted coating was obviously reduced in size compared with that in the sprayed coating, and its distribution was more even. Accordingly, the hardness, elastic modulus and fracture toughness of the remelted coating were greatly enhanced compared with the sprayed coating. Under dry friction condition, the wear resistance of the two coatings was significantly superior to that of the substrate. Compared with the sprayed coating, the friction coefficient of the remelted coating was slightly smaller, and the wear volume was reduced by 33.1 %. Therefore, the microstructure of Al-20Si/Cu-8P high‑silicon aluminum alloy coating was significantly improved and its properties was obviously enhanced by laser remelting and refinement.