Residual stress development and stability of Cr2AlC MAX phase coatings under thermal loading

热载荷下 Cr2AlC MAX 相涂层的残余应力发展和稳定性

• 批准号: 345199731
• 负责人: Professor Dr.-Ing. Christoph Leyens
• 金额: --
• 依托单位: Institut für Werkstoffwissenschaft
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/345199731?language=en
• 关键词: Residual; stress; development; stability; Cr2AlC

Surface coatings to improve oxidation and wear resistance for components are state of technology since many years. However, a continuous effort in research of new coating material is present, which show an optimal protection and thus lead to an optimization of processes e.g. concerning the efficiency. Cr2AlC, belongs to MAX-phases which have ceramic and metallic properties as well as excellent oxidation resistance. Hence this material has great potential as oxidation and wear resistant coatings.A crucial impact factor on coating characteristics and lifetime are residual stresses. With a selective generation of residual stresses in the component's surface it is possible to extend lifetime in a great amount. On the other hand thermal induced residual stresses caused by large differences in thermal expansion coefficients during thermo-cyclic exposure may result in catastrophic coating failure. Up to now, there is no work published about the stability of residual stresses and therefore the durability of the properties of Cr2AlC coatings at elevated as well as high temperatures. However, the knowledge of this issue is crucial for the application of thin films at thermal exposure. Additional there are no results known about the influence of chromium carbide and alumina phase formation due to the selective oxidation of aluminum as a result of oxidation of Cr2AlC and the residual stress development and film characteristics. Although the great amount in structural changes seem to influence it clearly.In the present proposal the research of the residual stress development and stability in thin Cr2AlC films in dependency of the deposition parameters, the substrate, the thermal and thermomechanical treatment as well as the oxidation including all processes associated with phase formation and transformation is conducted. These investigations are performed to contribute to the understanding in residual stress development in thin films as well as to investigate the ability of Cr2AlC coatings as oxidation and wear resistance coatings. In this project we perform isotherm and thermocyclic in situ high temperature x-ray diffraction (xrd) measurements combined with ex situ xrd analysis of coatings from long term treatments in isotherm and thermocyclic furnaces. Due to the complex processes which occur during oxidation, the experiments will be done in vacuum and oxidation atmosphere, to separate the thermal influence from the impacts through oxidation. Erosion experiments should permit an evaluation of the resistance of Cr2AlC coatings under mechanical and/or thermal exposure, taking into account the influence of residual stresses and phase development through oxidation.The analysis of the relaxation processes of residual stresses in thin films as well as failure mechanism are carried out additionally. Therefore it allows a widespread evaluation of processes during thermal and mechanical load.

多年来，用于提高部件抗氧化性和耐磨性的表面涂层一直是技术发展水平。然而，人们不断努力研究新的涂层材料，这显示出最佳的保护，从而导致工艺的优化，例如：关于效率。 Cr2AlC属于MAX相，具有陶瓷和金属特性以及优异的抗氧化性。因此，这种材料作为抗氧化和耐磨涂层具有巨大的潜力。影响涂层特性和寿命的一个关键因素是残余应力。通过在部件表面选择性地产生残余应力，可以大大延长使用寿命。另一方面，热循环暴露期间热膨胀系数的巨大差异引起的热诱导残余应力可能导致灾难性的涂层失效。到目前为止，还没有关于残余应力稳定性以及 Cr2AlC 涂层在高温和高温下性能耐久性的研究发表。然而，了解这个问题对于薄膜在热暴露方面的应用至关重要。此外，还没有关于由于 Cr2AlC 氧化导致铝选择性氧化而导致的碳化铬和氧化铝相形成的影响以及残余应力发展和薄膜特性的结果。尽管大量的结构变化似乎对其产生了明显的影响。在本提案中，研究了 Cr2AlC 薄膜中残余应力的发展和稳定性与沉积参数、基材、热处理和热机械处理以及氧化的关系。包括进行与相形成和转变相关的所有过程。进行这些研究是为了有助于了解薄膜中残余应力的发展，并研究 Cr2AlC 涂层作为抗氧化和耐磨涂层的能力。在该项目中，我们对在等温炉和热循环炉中长期处理的涂层进行等温和热循环原位高温 X 射线衍射 (xrd) 测量，并结合异位 xrd 分析。由于氧化过程中发生的复杂过程，实验将在真空和氧化气氛中进行，以将热影响与氧化影响分开。侵蚀实验应允许评估 Cr2AlC 涂层在机械和/或热暴露下的耐受性，同时考虑残余应力和氧化相发展的影响。薄膜中残余应力的松弛过程以及失效分析机制额外进行。因此，它可以对热负载和机械负载期间的过程进行广泛的评估。