外加应力及含水蒸气环境中CoNiCrAlY涂层表面氧化层的生长机制研究

活性元素（如Y，Hf等）掺杂CoNiCrAl涂层高温生成致密氧化层，是结构部件或热障涂层抗氧化腐蚀的保证。高温燃气中水蒸气含量增加的同时，外加应力也成为影响CoNiCrAl涂层氧化行为的重要因素。为了理解新环境中涂层的抗氧化性能，本项目研究外加应力和含H2O气氛同时对CoNiCrAlY涂层氧化层生长行为的影响，主要内容包括：不同外加应力（集中应力或循环应力）和H2O对活性元素(如Y和Hf)掺杂CoNiCrAl涂层的动力学定量影响，以及对氧化铝晶界和界面缺陷生长的影响规律，氧化初期外加应力和水蒸气对θ→α-Al2O3相变过程中能垒大小的影响；外加应力和H2O对α-Al2O3的组织结构（晶粒取向和尺寸分布）交互影响，氧化过程中H2O和外加应力对涂层表面尖晶石和其它氧化物形核和生长的影响机制；明确新条件下氧化铝界面的弱化机理，明确H2O和外加应力对合金氧化膜宏观缺陷演化的影响。

Dense oxide layer formed on the surface of CoNiClAl alloy coating doped by reactive elements (REs) could increase oxidation resistance properties of the components or thermal barrier coatings at high temperature under applied stress. With increasing of water vapor content in the combustion fuel, applied stress is becoming one of important factors to affect the oxidation behavior of CoNiCrAl coatings compared to that oxidized in dry air. Effect of reactive elements within the coatings on the oxidation behavior of CoNiCrAl alloy will be investigated during steam exposure at high temperature under complex applied stress (such as stress value, type and frequency) in this project...Effect of water vapor at high temperature on the thermodynamics and kinetics of CoNiCrAl alloy doped by REs, e.g. Y, Zr and Hf will be studied under applied stress. The detailed mechanism of influence of applied stress and water vapor on the defects within the alumina layer will be clearly analyzed. The phase transformation θ→α-Al2O3，especially the energy barrier during the above phase transformation, affected by REs and water vapor at the initially oxidation stage for the coatings under applied stress will be focused in this project. ..Another important research work in this project is how applied stress and water vapor affect the microstructure (grain orientation and size) of alumina layer and defects along alumina grain boundies as well as voids located at interface of the alumina/alloy coating. The detrimental oxides, e.g. spinel and others oxides nucleation and growth promoted by water vapor will also be studied through the measurement and calculation in order to suppress or hinder spinel formation...Residual stress concentration and cracks growth in the alumina oxide layer during the increasing and decreasing temperature stage within one cycling in humid air, especially under applied stress environment, will be the third research work in this project. The reason for the decreasing adhrence of alumina on the condition that the above new environment will be focused in this project. The mechanism about the effect of water vapor and applied stress on the defects (such as holes and cracks) within alumina on the CoNiCrAl alloy will be investigated in detail.