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

多层陶瓷和陶瓷-金属涂层的实施由于过早失效而受到限制。 迄今为止，对这些故障还没有令人满意或充分的了解。 大多数故障是由热机械载荷与一系列动态演变的材料特性的复杂相互作用引起的。 由于热暴露、氧化、电迁移和/或环境侵蚀等因素产生的使用中化学变化，材料特性会发生变化。 这些变化导致固有强度降低、内部应力重新分布和残余应力。 目前的工作重点是确定和相关的性能变化，过早失效的多层陶瓷和陶瓷-金属涂层。 为了了解故障的机械和物理机制，将实验和建模相结合的研究工作是必不可少的。 在实验上，微结构的演变将使用TEM、SEM、纳米压痕和其他适当的方法在适当的不同空间尺度（例如纳米、微米、介观）下表征。 空间分布，化学成分，和其他影响热机械性能的因素将在不同的温度循环下的使用寿命的各个部分进行表征。 根据该实验表征序列，将沿着相关机械过程识别材料降解的演变状态。 将开发分析和数值模型来模拟故障机制，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。 示例范围从保护燃气涡轮机叶片免受发动机中的高燃烧气体温度影响的热障涂层，到髋关节或膝关节植入物上的生物相容性涂层，以改善人体内的体内性能和生物相容性。 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。以及材料研究部（陶瓷）和国际办公室（西欧）作为NSF和EC之间的材料研究合作活动（NSF 03-565）。该项目是与下列机构合作执行的：西班牙加泰罗尼亚理工大学;西班牙陶瓷和玻璃研究所;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;德国德国航空航天中心;以及联合王国谢菲尔德大学。

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.