Development of strain tolerant aluminia scasles on MCr-AL-Basis high temperatur alloys and coatings

最近的研究结果表明，mcal型（M=Fe, Ni/CO）合金和涂层上的氧化铝保护膜的抗剥落性在很大程度上取决于保护膜的微观结构，因为含有微观结构缺陷（如纳米级孔隙和裂纹）的保护膜通常比几乎没有缺陷的均匀氧化铝膜具有更高的断裂韧性。氧化物的显微组织在很大程度上可以通过改变少量合金（涂层）成分和采用适当的表面预处理来控制。在拟议的项目中，后一种参数对氧化铝鳞片中氧化物晶粒尺寸和孔隙形成的影响将被定量评估。将推导出氧化物微观结构、等温氧化动力学和形成的鳞片断裂韧性之间的定量关联。尺度性质将通过一系列分析技术来表征，重点是定量SEM研究和应力测量。从这些研究中获得的知识可以作为开发具有延长使用寿命的mcal型合金（涂层）的指导方针。

Recently available results indicate that spallation resistance of the protective alumina scales on MCrAl-type (M=Fe, Ni/CO) alloys and coatings crucially depends on the scale microstructure because scales containing microstrutural defects, such as nano-sized pores and cracks often exhibit a higher fracture toughess, than virtally defect-free, uniform alumina films. The oxide microstructure can, to a large extent be controlled by modifying the minor alloy (coating) composition and by using suitable suface pre-treatments. In the proposed project the effect of the latter parameters on the oxide grain size and porosity formation in the alumina scales will be quantitatively assessed. A quantitative correlation between the oxide microstructure, isothermal oxidation kinetics and fracture toughness of the formed scales will be derived. The scale properties will be characterised by a range of analytical techniques with emphasis on quantitative SEM studies and piesospectroscopic stress measurements. The knowledge derived in these studies can be used as a guideline for development of MCrAl-type alloys (coatings) with extended service lives.