The Design and Analysis of Aluminide Surface Layers for Low Temperature Synthesis

这项研究的重点是了解一种创新的低温合成方法，以获得在高温处理过程中不会导致合金钢性能退化的抗氧化铝化物涂层。必须解决在低温下形成大铝熔剂的机制，以提供基本的理解，从而实现强有力的过程控制。Al5Fe2相是反应途径的重要组成部分，具有较高的晶格缺陷含量。定量的涂层生长动力学分析将证实Al5Fe2相在促进低温合成方面的作用。检查Al5Fe2相的稳定性将有助于了解缺陷结构和扩散动力学。虽然快速动力学在初始涂层合成中是一个优势，但在使用过程中它是一个令人担忧的问题，因为它会导致铝的耗尽和氧化保护的丧失。为了解决延长寿命的问题，将对多组分扩散路径进行评估，以便采用新的动力学偏置策略来开发原位扩散势垒和柔顺层，作为综合涂层设计的一部分。该研究在理解和控制低温铝化物涂层合成反应方面的进展将产生对支配动力学机制的更深层次的基础知识。引入一种新的动力学偏置策略以开发原位扩散势垒，将提供实现低温合成所需的关键缺失成分，作为在能源转换应用中保护合金钢的有效手段，从而提高发电量和效率。本研究开发的涂层设计策略作为一种经济有效的手段，在提高结构材料在高温侵蚀性环境下的耐降解性方面具有普遍的应用价值。该项目努力的一个重要组成部分将是研究生的教育。此外，有关涂料合成的讲座演示将被纳入高中和即将入学的本科生的外展计划中。

The focus of the research is to develop an understanding of an innovative low temperature synthesis pathway for oxidation resistant aluminide coatings without degradation of alloy steel properties that occurs with high temperature processing. The mechanism that enables the development of a large Al flux at low temperature must be resolved to provide the fundamental understanding that will allow for a robust process control. The Al5Fe2 phase appears to be an important component of the reaction pathway and is characterized by a high lattice defect content. A quantitative coating growth kinetics analysis will be conducted to confirm the role of the Al5Fe2 phase in enhancing low temperature synthesis. An examination of the stability of the Al5Fe2 phase will allow for an understanding of the defect structure and diffusion kinetics. While the rapid kinetics is an advantage in initial coating synthesis, it is a concern during service since it results in depletion of Al and the loss of oxidation protection. In order to address the lifetime extension the multicomponent diffusion pathways will be assessed so that a novel kinetic biasing strategy can be employed to develop in-situ diffusion barriers and compliant layers as part of an integrated coating design.The advancement in the understanding and control of low temperature aluminide coating synthesis reactions resulting from the research will yield a deeper fundamental knowledge of the governing kinetic mechanisms. The introduction of a novel kinetic biasing strategy in order to develop an in-situ diffusion barrier will provide a key missing component that is required in order to implement low temperature synthesis as an effective means to protect alloy steels in energy conversion applications to allow for increased power generation and efficiency. The coating design strategies developed in this research have a general application as a cost effective means to enhancing the resistance of structural materials to degradation under aggressive environments at high temperature. An important component of the project effort will be the education of a graduate student. Further, lecture demonstrations on coating synthesis will be incorporated into outreach programs for high school and incoming undergraduate students.