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以常规和纳米团聚体ZrO2-7%Y2O3陶瓷粉末为原料,采用等离子喷涂和等离子喷涂+激光重熔复合工艺在TiAl合金表面制备了常规和纳米结构热障涂层。用扫描电镜(SEM)分析了粉末结构及制备工艺对涂层显微组织的影响。结果表明:用常规等离子喷涂法制备的陶瓷涂层为典型的层状堆积特征;而用等离子喷涂法制备的纳米结构涂层则由纳米颗粒完全熔化区和部分熔化区组成,呈两相结构。由于受到激光功率、能量密度、激光作用区温度场分布、陶瓷导热系数和涂层厚度等因素的综合影响,经激光重熔后,涂层呈现出明显的分层结构特征:上部为致密的柱状晶重熔区,下部为残余等离子喷涂区。由于激光重熔纳米结构涂层重熔区中残余纳米粒子的增韧作用,其晶界强度较高,从而导致断口有相当数量的穿晶断裂,而激光重熔常规涂层重熔区的断口基本是沿晶断裂。
Conventional and nanostructured ZrO2-7% Y2O3 ceramic powders were used as raw materials to prepare conventional and nano-structured thermal barrier coatings on TiAl alloy by plasma spraying and plasma spraying + laser remelting. The effect of powder structure and preparation process on the microstructure of the coating was analyzed by scanning electron microscopy (SEM). The results show that the ceramic coating prepared by the conventional plasma spraying method is a typical lamellar stacking characteristic. The nanostructured coating prepared by plasma spraying method is composed of a completely melted region and a partially melted nanoparticle, and has a two-phase structure. Due to the combined influence of laser power, energy density, temperature field distribution in laser action zone, thermal conductivity of ceramic and thickness of coating, the coating shows obvious layered structure after laser remelting: the upper part is dense columnar Crystal heavy melting zone, the lower part of the residual plasma spraying zone. Due to the toughening effect of residual nanoparticles in the remelted zone of the laser remelted nanostructured coating, the grain boundary strength is higher, resulting in a considerable amount of transgranular fracture of the fracture, whereas the fracture of the remelted zone of the laser remelted conventional coating The basic is along the crystal break.