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

该研究的重点是开发一种创新的低温合成途径，用于抗氧化铝化物涂层，而不会因高温加工而导致合金钢性能下降。必须解决在低温下开发大铝通量的机制，以提供基本的理解，从而实现稳健的过程控制。Al5Fe2相是反应途径的重要组成部分，其特点是晶格缺陷含量高。将进行定量的涂层生长动力学分析，以证实Al5Fe2相在增强低温合成中的作用。检查Al5Fe2相的稳定性将有助于了解缺陷的结构和扩散动力学。虽然快速动力学在初始涂层合成中具有优势，但由于它会导致Al的消耗和氧化保护的丧失，因此在使用过程中是一个值得关注的问题。为了解决寿命延长的问题，我们将评估多组分扩散路径，以便采用一种新的动力学偏置策略来开发原位扩散屏障和柔性层，作为集成涂层设计的一部分。在对低温铝化物涂层合成反应的理解和控制方面取得的进展将使我们对控制反应的动力学机制有更深入的认识。为了开发原位扩散屏障，引入了一种新的动力学偏置策略，这将提供一个关键的缺失组件，这是实现低温合成所需的一个有效手段，以保护合金钢在能量转换应用中，从而提高发电量和效率。本研究中开发的涂层设计策略作为一种经济有效的手段，在高温侵蚀环境下增强结构材料的抗降解能力，具有普遍的应用价值。项目工作的一个重要组成部分将是研究生的教育。此外，有关涂层合成的讲座示范将纳入高中和即将入学的本科生的拓展计划。

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.