镍基单晶合金力学-氧化/热腐蚀耦合作用下的损伤失效机理和寿命模型

The need for carrier-based aircraft is very urgent with the implementation of the marine power strategy of our nation. The service conditions are harsher for the matching engine. The nickel base single crystal superalloy is the key material of the engine blade. It has to bear the salt spray corrosion caused by the sea environment in addition to high temperature and high load working conditions. The mechanical behavior and high temperature oxidation/hot corrosion interact with each other, which leads to the changes of material performance. Traditional performance data and analytic method are no longer applicable. In this project, the performance and damage failure of the material will be studied considering the mechanics-oxidation/hot corrosion interaction under corrosion environment and loading condition on the sea. The influences of load on the oxidation/hot corrosion properties as well as the influences of corrosion medium on the strength and life of the material will be investigated. The microstructure and its evolution will be studied experimentally and theoretically using thermal dynamics, element diffusion and phase field calculation theories. The mechanisms of damage and failure will be revealed under mechanics-oxidation/hot corrosion interaction. The micro-controlling factors will be quantitatively extracted as representative variables to describe deformation, damage and failure of the material. Based on the micro-mechanisms, the consititutive model and life prediction model will be established and implemented into finite element program. The study can reveal the failure mechanism of the nickel based single crystal alloy under mechanics-oxidation/hot corrosion interaction. Experimental data and theoretical model can be directly used for analysis of blade strength and life under corrosion environment. Therefore, this project has important theoretical research value and broad application prospect.

海洋强国战略的实施给配备于舰载机的发动机提出更为恶劣的服役环境。镍基单晶合金作为发动机涡轮叶片的关键材料，除了承受高温高载还必须承受海上的盐雾腐蚀作用。高温氧化/热腐蚀和力学行为之间相互影响，导致材料性能变化，传统性能数据和分析方法不再适用。本项目拟针对海上服役腐蚀环境和载荷工况，开展力学-氧化/热腐蚀耦合作用下的材料性能及损伤失效研究：探究载荷工况下的氧化/热腐蚀动力学特性和腐蚀介质对强度/寿命的影响规律；从细微观组织结构及其演化出发，结合热动力学、元素扩散和相场计算等理论，揭示力学-氧化/热腐蚀耦合作用下的损伤失效机理；提取控制材料变形、损伤和失效的细微观特征量，基于晶体塑性理论，建立本构模型和寿命模型；完成相应的有限元程序开发。该研究可揭示力学-氧化/热腐蚀耦合作用下的失效机理，试验数据和理论模型可直接用于腐蚀环境下的叶片强度/寿命分析，具有重要的理论研究价值和广泛的工程应用前景。

镍基单晶涡轮叶片是航空发动机最关键的核心部件，在一定程度上直接决定了发动机的性能。随着我国海洋强国战略的实施，舰载机的投入使用，需要考虑海洋环境引起的高温热腐蚀对镍基单晶合金性能的影响。本项目针对这种高温热腐蚀环境，考虑工作时的载荷工况，研究其力学-氧化/热腐蚀耦合作用下的力学性能。采用目前广泛应用的第二代镍基单晶合金材料，进行了氯化钠、硫酸钠以及混合盐作用下的试验研究。采用扫描电子显微镜对试样的微观组织形貌及其演化进行了分析。采用相场理论，力学-化学耦合理论进行了微观结构演化的模拟分析。理论和试验结合揭示氧化/热腐蚀作用下的失效机理。试验结果表明，低温盐雾腐蚀对镍基单晶合金的细微观形貌基本没有影响，而高温下的热腐蚀尤其是氯化钠腐蚀下对材料的破坏非常严重。涂敷腐蚀盐的试样其蠕变寿命均比未涂敷试样大幅度降低。微观形貌分析表明，高温氧化环境导致材料微观结构发生分层和筏化，而由于腐蚀盐造成的化学反应导致腐蚀产物出现，元素扩散加剧，尤其是含有氯元素时还将生成氯气，在试件内部造成大量的孔洞，从而造成了材料性能的进一步劣化。在试验研究的基础上，基于元素扩散和化学反应，建立了力学-化学耦合的蠕变本构模型及寿命模型，并结合商用有限元软件ABAQUS，实现了模型的程序化。本项目的研究可为镍基单晶叶片在海上或类似的腐蚀服役环境下的提供宏观力学性能数据，并为其强度/寿命分析设计提供理论方法和程序，具有重要的理论价值和工程应用前景。