镁合金AZ91HP表面激光重熔Al2O3涂层的组织及性能

采用等离子喷涂和激光重熔复合工艺在AZ91HP镁合金表面制备了Al2O3陶瓷涂层.结果表明,由于受激光作用区温度场分布、陶瓷材料热物性参数和涂层厚度等因素的综合影响,激光重熔Al2O3涂层呈现出明显的分层结构特征.依据组织结构不同,可将其分为:由α-Al2O3柱状晶构成的表面熔凝区、具有团絮状形貌特征的烧结区以及保持原喷涂态结构特征的残留等离子喷涂层.由于激光重熔陶瓷涂层表面单相α-Al2O3柱状晶的形成,使其硬度及耐磨、耐蚀性均明显优于等离子喷涂Al2O3涂层和原始镁合金.

MICROSTRUCTURE AND PROPERTIES OF Al2O3 CERAMIC COATING BY PLASMA SPRAYING AND LASER REMELTING ON MAGNESIUM ALLOY

Al2O3 ceramic coating is prepared by plasma spraying and laser remelting on AZ91HP Mg alloy. The results show that the plasma-sprayed Al2O3 coating consists of -Al2O3 and -Al2O3 phases with the macrostructure of lamellar stacking. After laser remelting, the coating exhibited obvious layer characteristic due to influence of temperature distribution, thermophysical parameters and layer thickness. According to the microstructural difference, the coating can be divided into the melted zone composed of the -Al2O3 columnar crystal, the sintered zone with flocculent-structure characteristic, the residual plasma-sprayed layer with loosen structure, Al-Si transition layer and the substrate. Because of fine structure and high density, the hardness, wear and corrosion resistances of the laser remelted coating are much higher than those of the plasma-sprayed coating and as-received Mg alloy.