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.

从多年来开始，表面涂层以改善组件的氧化和耐磨性是技术的状态。但是，存在着对新涂料材料进行研究的持续努力，这表明了最佳保护，从而导致了过程的优化，例如关于效率。 CR2ALC属于具有陶瓷和金属特性以及出色的氧化耐药性的最大浓度。因此，由于氧化和耐磨涂层，这种材料具有很大的潜力。涂层特征和寿命的关键影响因素是残留应力。在组件表面有选择性产生的残余应力，可以大大延长寿命。另一方面，热诱导的残留应力是由热循环暴露期间热膨胀系数较大的较大差异引起的，可能会导致灾难性的涂层破坏。到目前为止，还没有关于残余应力的稳定性以及CR2ALC涂层在升高和高温下的性质的持久性的发表。但是，对此问题的了解对于在热暴露时应用薄膜至关重要。由于CR2ALC的氧化以及残留的应力发展和膜特征，由于铝和氧化氧化而导致的碳化物和氧化铝相的影响尚无结果。尽管结构变化的大量变化似乎很清楚地影响了它。在当前提案中，稀薄的CR2ALC膜中残留应力发展和稳定性的研究依赖沉积参数，基板，热力学处理以及氧化以及包括与相形成和转化相关的所有过程。进行这些研究是为了有助于薄膜中残留应力发展的理解，并研究CR2ALC涂层作为氧化和耐磨性涂层的能力。在这个项目中，我们执行等温线和热环状原位高温X射线衍射（XRD）测量，并结合了异位和热环熔炉中长期处理的涂层的事前XRD分析。由于在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，以将热影响与通过氧化的影响分开。侵蚀实验应允许在机械和/或热暴露下评估CR2ALC涂层的耐药性，并考虑到残留应力和通过氧化的影响。分析薄膜中残留应力的松弛过程以及故障机制的残余应力过程。因此，它允许对热和机械负载期间的过程进行广泛的评估。