超高温蠕变过程中含Ru镍基单晶合金性能退化的微观动力学机制

Super-high temperature creep damage under extreme conditions is one of the main reasons that lead to the degradation of properties of Ni-base single crystal superalloys. The project will be carried out with the aid of advanced high temperature creep tester, scanning electron microscope (SEM) and high resolution scanning transmission electron microscope (HRSTEM). In order to obtain an in-depth understanding of the creep behavior of Ru-containing Ni-base single crystal superalloy under the non-isothermal and isothermal super-high temperature conditions, the effects of strengthening elements, such as Ru et al., will be clarified. And then, the microstructural evolution of the widening of γ phase, the precipitation of small γ′ phase and topologically close-packed (TCP) phase, the dissolution, re-precipitating and rafting of γ′ phase will be revealed to understand the intrinsic creep damage during the non-isothermal super-high temperature creep. Apart from those, as important deformation mechanisms, the roles of dislocation configuration and creep holes during super-high temperature creep also will be emphasized. Based on these analyses, the micro-dynamic mechanisms of properties degradation of Ru-containing Ni-base single crystal superalloy during super-high temperature creep will be rationalized and the super-high temperature creep damage will be quantitatively evaluated. This project may offer a theory support for the development of advanced Ni-base single crystal superalloys.

超高温条件下蠕变损伤是导致镍基单晶合金性能退化的关键因素之一。本项目拟借助先进（超）高温蠕变试验机、扫描电镜（SEM）、高分辨扫描透射电镜（HRSTEM）等实验分析手段，系统研究含Ru镍基单晶高温合金的非等温和等温超高温蠕变行为，明确Ru等强化元素在超高温蠕变过程中的作用，揭示镍基单晶高温合金超高温蠕变过程中γ基体相的宽化、细小γ′相的析出、γ′相的溶解、析出以及筏化、拓扑密排（TCP）相的析出等微观结构的演化，阐明位错、孔洞等缺陷在蠕变过程中的作用机制。在此基础上，探讨超高温过程中镍基单晶高温合金的蠕变性能退化的微观动力学机制，定量评估超高温对合金造成的损伤，为发展高性能的镍基单晶高温合金材料提供理论依据。

镍基单晶高温合金由于具有优异高温强度、良好的抗氧化腐蚀性能等而被广泛用于制造先进航空发动机和燃气轮机的涡轮叶片，是目前先进动力推进系统不可或缺的关键材料。超高温蠕变性能是衡量镍基单晶高温合金力学性能的重要指标之一，也是发动机涡轮叶片材料选择的基础。超高温必然会导致单晶合金的微观组织发生变化，进而会影响高温结构部件的长期服役可靠性。本项目以下一代发动机用含Ru先进镍基单晶高温合金为研究对象，主要研究了合金的等温和非等温超高温蠕变行为。研究表明，合金在等温超高温蠕变寿命显著降低（1个数量级），而在非等温蠕变条件且不同蠕变阶段（第一、二阶段）短时超温不同时间后合金的蠕变寿命基本保持不变，蠕变应变增量与蠕变阶段的选择基本无关，且在一定的蠕变超温时间内蠕变应变增量基本保持不变，这与先前报道（出现明显的超温蠕变损伤）明显不同，表明实验合金具有优异的抗高温蠕变损伤性能。上述研究对于揭示含Ru镍基单晶合金的真实蠕变行为、定量评估超高温对含Ru镍基单晶合金服役行为的影响提供了重要数据支撑，同时亦为发展新型单晶高温合金合金材料及其实际服役提供了参考。