热障涂层中热生长氧化物的固体反应流理论

Reactive flow in solids is the concurrent plastic flow with chemical reaction. It is different corresponding to different reaction mechanisms.There are already, some reactive flow theories now, such as on the lithium-ion batteries and on gels. However, there has not been perfect theory on the plastic flow with oxidation of metal. The following special features of metal oxidation induce the difference of reactive flow theory. (1) The phases of oxides coexist with phases of metals and there are sharp phase boundaries.(2) The oxidation occurs, in fact, in the oxide scale due to the inner diffusion of ions.(3) There may be phase transformation in the process of oxidation. The growth and plastic flow of TGO in thermal barrier coatings (TBCs) is a typical reative flow. This project is aimed to set up a reactive flow theory corresponding to the TGO in TBCs. Wagner's oxidation mechanism of solids are adopted. The chemo-thermo- mechanical coupled effect the phase transformation in oxidation process are considered in this theory. Firstly, we will investigat the oxidation mechanism, the morphology and the stress distribution in TGO through experiments. Then we will set up the reative flow theory by Gibbs's thermodynamical theory to predict the plastic deformation of TGO.The theoratical results will be testified by the experiments. This theory will not only be valid for the TGO growth in TBCs, but also valid for other solid reaction with phase transformation.

固体反应流指包含化学反应的固体塑性流动理论。不同的化学反应机理对应的反应流理论也有区别。目前关于锂电池与凝胶等化学反应变形方面已经有相应的固体反应流理论。然而金属氧化与塑性变形的固体反应流理论并未完全建立。金属氧化有以下特点导致其反应流理论的特殊性：（1）反应过程中氧化物相与金属相相共存，存在相边界；（2）反应在氧化物中发生；（3）随反应的进行，合金的氧化物可发生相变。热障涂层中TGO生长流动过程是典型的固体反应流过程。本研究拟建立热障涂层中TGO生长与变形的固体反应流理论。该理论满足Wagner氧化理论，包含化学-热-力耦合关系，并能够计及固体反应中的相变。首先通过实验分析TGO中的反应机理、形貌、及应力分布。利用Gibbs化学热力学原理建立固体反应流本构，预测TGO的反应流动，并用实验测试结果进行校核。该理论将不仅适用于热障涂层中TGO的反应流动，也适用于其他存在相分离的固体反应流动。

重型燃气轮机服役周期长，启停次数少，其高温叶片热障涂层长期处于等温氧化环境中，热生长氧化物不断生长累积，形成巨大的生长应力，其对热障涂层失效的影响不可忽略。本项目通过对热障涂层粘结层的氧化实验，发现了氧化铝生长的相变规律及应力影响规律；建立了计算模型，分析了热生长氧化物生长速度对界面强度的影响，指出了TGO生长速度是造成重型燃气轮机热障涂层失效的关键因素；建立了理论模型，分析了热障涂层界面损伤发生后，温度和热应力的分布规律，为热障涂层寿命评估与检测提供了依据。通过此项目的进行，明确了重型燃气轮机与航空发动机热障涂层的服役特征及设计指标的差别，为有针对性地改进重型燃气轮机热障涂层提供了依据。