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Oxidation Damage at a Crack Tip and Its Significance in Crack Growth under Fatigue-Oxidation Conditions

疲劳氧化条件下裂纹尖端的氧化损伤及其在裂纹扩展中的意义

基本信息

批准号：
EP/K026844/1
负责人：
Liguo Zhao
金额：
$ 31.1万
依托单位：
Loughborough University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FK026844%2F1
关键词：
Oxidation Damage Crack Tip Its

项目摘要

Nickel-based alloys are widely used in power generation, nuclear and aerospace industries due to their superior mechanical properties at high temperature. As structural materials, a strong resistance to crack initiation and propagation is particularly required for safe-life design and assessment of their components. At elevated temperature, crack growth rates in such alloys exposed to air can be drastically accelerated, by two and even three orders of magnitude, due to the attack of oxidation. Over time, significant effort has been made to investigate the crack tip oxidation mechanism in order to provide a basis for the development of quantitative models that predict crack growth under operational temperatures and loading conditions. However, this problem has been neither fundamentally nor fully understood, and current lifing practice in industries is still predominantly empirical and relies on expensive and extensive experimental data on crack growth.This research aims to investigate the physical process of oxidation damage at a crack tip and the associated crack growth behaviour for nickel alloys, which will provide a direct insight, for the first time, into the oxidation-embrittlement phenomenon at crack tip. Oxidation damage at a crack tip is a combined effect of time, temperature, local deformation and material microstructure. Knowledge of this process is vital to assess crack propagation behaviour under the attack of oxidation. In the proposed work, single crystal, directionally solidified and polycrystal nickel alloys will be used for crack growth testing under fatigue-oxidation conditions in controlled environments (vacuum, air, oxygen-18). Advanced microscopy analyses will be carried out to characterise and measure the oxygen penetration and microstructural damage at a crack tip, and the results will be used to calibrate important diffusion and damage parameters during oxidation. Numerical analyses will be carried out to model such processes at a microscopic scale using a coupled mechanical-diffusion model. Effects of loading condition and grain boundary character on oxygen diffusion will be fully investigated, especially the connection between oxidation damage and crack growth. A crack propagation model will be ultimately developed and validated for accurate fatigue-oxidation life prediction.The work draws together three established groups to tackle these fundamental problems in a collaborative, systematic and multi-scale manner. Interaction between oxidation damage and crack tip deformation requires carefully designed specialist testing on fatigue crack growth in a controlled environment, which is the expertise of UoS. The problem also requires advanced microscopy characterisation and physical measurements of the phenomena using the established techniques at IC. The new models will be developed, with validation against these experimental results, by UoP who has a strong background in material and crack growth modelling. Owing to our complementary skills, this joint project should establish a physically based connection between oxidation damage and crack growth for fatigue design and safe life prediction of nickel alloy components. The research will generate unique and practically-useful data and models which can be quickly exploited through our committed industrial collaborators including E.On, Alstom, NASA and Dstl. The results will also be of generic use to other industries striving to achieve maximum service life and temperature capabilities of critical high-temperature components. Researchers and academics working on high-temperature materials and related areas will also directly benefit from our targeted dissemination activities including workshops, conferences and journal papers. A wider audience will be reached via specially designed public engagement programmes and continuously updated web sites.

镍基合金因其优越的高温机械性能，在发电、核能和航空航天工业中得到了广泛的应用。作为结构材料，对其构件的安全寿命设计和评估尤其要求具有较强的抗裂纹萌生和扩展能力。在高温下，由于氧化作用，暴露在空气中的这种合金的裂纹扩展速度会急剧加快，速度可达两个甚至三个数量级。随着时间的推移，人们对裂纹尖端氧化机理进行了大量的研究，以便为在工作温度和载荷条件下预测裂纹扩展的定量模型的发展提供基础。然而，这个问题既没有从根本上理解，也没有完全理解，目前工业上的生活实践仍然主要是经验主义的，依赖于昂贵而广泛的裂纹扩展实验数据。本研究旨在研究镍合金裂纹尖端氧化损伤的物理过程和相关的裂纹扩展行为，这将首次为裂纹尖端氧化脆化现象提供直接的见解。裂纹尖端氧化损伤是时间、温度、局部变形和材料显微组织的综合作用。了解这一过程对于评估氧化作用下裂纹扩展行为是至关重要的。在这项工作中，单晶、定向凝固和多晶镍合金将在受控环境（真空、空气、氧-18）的疲劳氧化条件下进行裂纹扩展试验。先进的显微分析将用于表征和测量裂纹尖端的氧气渗透和微观结构损伤，结果将用于校准氧化过程中重要的扩散和损伤参数。数值分析将在微观尺度上使用耦合的机械扩散模型来模拟这些过程。研究了加载条件和晶界特征对氧扩散的影响，特别是氧化损伤与裂纹扩展之间的关系。裂纹扩展模型将最终开发和验证，以准确预测疲劳氧化寿命。这项工作将三个已建立的小组聚集在一起，以协作、系统和多尺度的方式解决这些基本问题。氧化损伤和裂纹尖端变形之间的相互作用需要在受控环境中对疲劳裂纹扩展进行精心设计的专业测试，这是UoS的专长。该问题还需要使用IC已建立的技术对现象进行先进的显微镜表征和物理测量。UoP将开发新模型，并根据这些实验结果进行验证，UoP在材料和裂纹扩展建模方面具有强大的背景。由于我们的技术互补，本次合作项目将建立基于物理的氧化损伤与裂纹扩展之间的联系，用于镍合金部件的疲劳设计和安全寿命预测。这项研究将产生独特而实用的数据和模型，这些数据和模型可以通过我们承诺的工业合作者，包括意昂、阿尔斯通、美国宇航局和Dstl，迅速加以利用。研究结果也将普遍用于其他行业，努力实现关键高温部件的最大使用寿命和温度能力。高温材料及相关领域的研究人员和学者也将直接受益于我们有针对性的传播活动，包括研讨会、会议和期刊论文。我们将透过特别设计的公众参与节目和不断更新的网站，接触更广泛的受众。