激光熔覆制备单晶MCrAlY涂层微结构调控及高温氧化行为研究

单晶MCrAlY涂层可缓解涂层与单晶高温合金基体之间的性能不匹配，提高叶片的服役寿命。前期研究结果表明，利用激光熔覆技术可以在单晶高温合金基体上外延生长单晶组织，这使制备MCrAlY单晶涂层成为可能。本项目拟在已有研究工作的基础上，以γ'单相组成的MCrAlY涂层材料为研究对象，采用实验验证和数值模拟相结合的方法，探明激光熔覆工艺参数与MCrAlY涂层枝晶生长行为和显微组织的响应关系，分析涂层外延生长过程中柱状晶向等轴晶转变这一激光熔覆关键问题的热力学和动力学，构建熔覆工艺参数与涂层微观组织结构的内在关系图，提出涂层微观组织结构的控制策略。在此基础上，研究激光熔覆MCrAlY涂层的高温氧化行为，阐明该MCrAlY涂层的损伤过程和失效机理，为今后发展单晶MCrAlY涂层奠定理论基础。

Single crystal MCrAlY coatings can reduce the property mismatch between the coating and single crystal superalloy substrate, and thus improve the component life time. Our previous study indicated that laser cladding can allow the epitaxial growth of a single-crystalline structure on a single crystal superalloy substrate, which makes the deposition of a single-crystal MCrAlY coating be technically feasible. However, the main limit to achieving a single crystalline structure in the deposition material is the possibility of a columnar to equiaxed solidification transition occurring when the solidification front approaches the surface. So, it is necessary to study the dendrite-growth rule to obtain a single crystal coating produced by laser cladding. Based on the previous research results, the present study will investigate the relation between the cladding processing parameters and the dendrite growth in the corresponding γ'-constituted MCrAlY coating through both experimental investigation and numerical computation. The thermodynamic and dynamic of the columnar to equiaxed transition during epitaxial deposition will also be analyzed, and the microstructure-processing map for the solidification of the multi-component MCrAlY coating alloy will be proposed. According to these results, the microstructure control strategy of the single crystal MCrAlY coating during laser cladding process will be suggested. Furthermore, the selective oxidation behavior and failure mechanisms of the single crystal MCrAlY coating at high temperatures will be investigated. The results obtained in the present study are expected to instruct the development of the single crystal MCrAlY coating deposition.