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

该研究的重点是了解一种创新的低温合成途径，用于抗氧化铝化物涂层，而不会降低合金钢在高温加工中的性能。必须解决在低温下能够形成大Al通量的机制，以提供基本的理解，从而实现稳健的工艺控制。Al5Fe2相似乎是反应途径的重要组成部分，其特征在于高的晶格缺陷含量。 将进行定量涂层生长动力学分析以确认Al5Fe2相在增强低温合成中的作用。的Al5Fe2相的稳定性的检查将允许的缺陷结构和扩散动力学的理解。虽然快速动力学在初始涂层合成中是一个优点，但在使用过程中它是一个问题，因为它导致Al的耗尽和氧化保护的损失。 为了解决寿命延长的多组分扩散途径将进行评估，以便一种新的动力学偏置策略可以采用开发原位扩散屏障和顺应层的一部分，集成coating design.The进步的理解和控制低温铝化物涂层合成反应的研究所产生的动力学机制将产生更深的基础知识。为了开发原位扩散阻挡层而引入新的动力学偏置策略将提供关键的缺失组分，该缺失组分是为了实施低温合成所需的，作为在能量转换应用中保护合金钢的有效手段，以允许增加发电量和效率。在这项研究中开发的涂层设计策略具有普遍的应用，作为一种具有成本效益的手段，以提高结构材料在高温下的侵蚀性环境下的抗降解性。该项目工作的一个重要组成部分将是研究生的教育。此外，关于涂料合成的讲座演示将纳入高中和即将入学的本科生的推广计划。

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.