NSF-EC Cooperative Activity in Materials Research: Failure Mechanics of Layered Ceramics and Ceramic-Metal Coatings Due to Environmental Exposure

由于过早失效，多层陶瓷和陶瓷-金属涂层的实施受到限制。到目前为止，对这些失败还没有令人满意或充分的理解。大多数失效是由热机械载荷与一系列动态变化的材料特性的复杂相互作用引起的。材料性能的演变是由于热暴露、氧化、电迁移和/或环境攻击等因素产生的使用中的化学变化。这些变化导致较低的固有强度、内部应力重新分布和残余应力。本工作的重点是确定多层陶瓷和陶瓷-金属涂层的性能变化，并将其与早期失效联系起来。为了了解故障的力学和物理机制，将实验和建模相结合的研究工作是必不可少的。在实验上，将利用透射电子显微镜、扫描电子显微镜、纳米压痕和其他适当的方法在适当不同的空间尺度(如纳米、微观、介观)表征微结构的演变。在不同的温度循环下，将在不同的使用寿命阶段表征材料的空间分布、化学成分和其他影响热机械性能的因素。根据这一实验表征序列，将识别材料降解的演变状态以及相关的机械过程。将开发分析和数值模型来模拟失效机制，将基本原理与实验观察联系起来，并提供对这些复杂系统的更好理解。这些模型将发表在行业期刊上，使设计工程师能够提高多层组件的性能。多层陶瓷和陶瓷/金属涂层用于一系列工程应用，以提高组件和结构的性能和功能。例子包括保护燃气轮机叶片免受发动机高温燃烧气体影响的热障涂层，到髋关节或膝盖植入物上的生物兼容涂层，以提高人体的体内性能和生物兼容性。不幸的是，陶瓷涂层有时过早失效，限制了它们在这些先进材料系统中的用途。这项研究旨在了解故障并开发预测数学模型，以帮助设计工程师在这些重要产品的未来版本中消除此类缺陷。该NSF项目由多学科活动办公室、材料研究司(陶瓷)和国际办公室(西欧)共同资助，作为NSF和EC之间在材料研究方面的合作活动(NSF 03-565)。该项目是与西班牙加泰罗尼亚理工大学、西班牙陶瓷与玻璃研究所、斯洛伐克斯洛伐克科学院、意大利陶瓷技术研究所、奥地利结构和功能陶瓷研究所、比利时鲁汶天主教大学、德国航空航天中心和英国谢菲尔德大学合作开展的。

The implementation of multilayered ceramics and ceramic-metals coatings is limited due to premature failures. To date no satisfying or adequate understanding of these failures exists. Most failures are caused by an intricate interaction of thermo-mechanical loads with an array of dynamically evolving material properties. The material properties evolve due to in-use chemical changes generated by factors such as thermal exposure, oxidation, electro-migration, and/or environmental attack. These changes result in lower intrinsic strength, internal redistribution of stresses, and residual stresses. The present work focuses on determining and relating property changes to pre-mature failures of multilayered ceramics and ceramic-metals coatings. In order to understand the mechanical and physical mechanisms of failures, a research effort that integrates experiment and modeling is essential. Experimentally, the evolution of the microstructure will be characterized using TEM, SEM, nano-indentation and other appropriate methods at appropriately different spatial scales (e.g. nano, micro, meso). The spatial distribution, chemical composition, and other factors influencing thermo-mechanical properties will be characterized at various fractions of service life under different temperature cycles. From this experimental characterization sequence the evolving state of the material degradation will be identified along with the associated mechanical processes. Analytical and numerical models will be developed to simulate the failure mechanisms, to link fundamental principles with experimental observations, and to provide a greater understanding of these complex systems. The models will be published in industry journals to enable design engineers to enhance multilayer component performance.Multilayered ceramics and ceramic/metal coatings are used in a range of engineering application to improve the performance and functionality of components and structures. Examples ranges from thermal barrier coatings that protect gas turbine blades from the high combustion gas temperatures in the engine, to bio-compatible coatings on hip or a knee implants to improve the in-vivo performance and bio-compatibility in humans. Unfortunately, ceramic coatings sometimes fail prematurely, limiting their usefulness in these advanced material system. This research aims to understand the failures and to develop predictive mathematical models that will assist design engineers in eliminating such flaws in future versions of these important products.This NSF project is co-funded by the Office of Multidisciplinary Activities, and the Division of Materials Research (Ceramics) and the International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and EC (NSF 03-565). This project is being carried out in collaboration with the Polytechnic University of Catalonia, Spain; Institute of Ceramic and Glass, Spain; Slovak Academy of Sciences, Slovakia; Research Institute for Ceramic Technology, Italy; Institute for Structural and Functional Ceramics, Austria; the Catholic University of Leuven, Belgium; the German Aerospace Center, Germany; and the University of Sheffield, UK.