Analysing the coupled effects of compressive and diffusion induced stresses on the nucleation and propagation of circular coating blisters in the presence of micro-cracks
Analysing the coupled effects of compressive and diffusion induced stresses on the nucleation and propagation of circular coating blisters in the presence of micro-cracks
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DOI：
10.1016/j.engfailanal.2016.07.003
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发表时间：
2016-12-01
影响因子：
4
通讯作者：
Stokes, K.
中科院分区：
文献类型：
--
作者：
Nazir, M. H.;Khan, Z. A.;Stokes, K.
本文提出了在残余压应力和扩散诱导应力的作用下微裂纹涂层分层的研究。涂层中的微裂纹为腐蚀性物质提供了通向涂层-基材界面的通道，进而在涂层中产生扩散诱导应力。由于热膨胀失配阻碍了物质向界面扩散，随着涂层中残余压应力的增加，微裂纹逐渐收缩。这种行为减少了涂层中扩散引起的应力，同时压缩残余应力增加。随着压缩残余应力的进一步增加，微裂纹达到无法进一步收缩的程度，高压缩残余应力导致涂层从基材上弯曲，导致分层，从而引发起泡。起泡导致收缩的微裂纹再次张开，这增加了扩散引起的应力以及高压缩残余应力。涂层中的高合成应力导致气泡以轴对称圆形图案传播。采用两部分理论方法将热力学概念与力学概念结合起来。热力学概念涉及腐蚀性物质在不断增加的压力下通过微裂纹的传输，最终导致起泡，而断裂力学概念用于将气泡生长视为圆形缺陷传播。讨论了模量比、厚度比、热失配比、泊松比和界面粗糙度对气泡生长的影响。报道了起泡实验，以允许界面可视化并允许在整个感兴趣范围内涂层中的耦合（扩散和残余）应力。模型的预测与实验结果显示出极好的定量一致性。 (C) 2016 Elsevier Ltd. 保留所有权利。
This paper presents a study of delamination of coating with micro-cracks under compressive residual stress coupled with diffusion induced stress. Micro-cracks in coating provide a passage for corrosive species towards the coating-substrate interface which in turn produces diffusion induced stress in the coating. Micro-cracks contract gradually with increasing compressive residual stress in coating due to thermal expansion mismatch which blocks the species diffusion towards the interface. This behaviour reduces diffusion induced stress in the coating while compressive residual stress increases. With further increase in compressive residual stress, micro-cracks reach to the point, where they cannot be constricted any further and a high compressive residual stress causes the coating to buckle away from the substrate resulting in delamination and therefore initiating blistering. Blistering causes the contracted micro-cracks to wide open again which increases diffusion induced stress along with high compressive residual stress. The high resultant stress in coating causes the blister to propagate in an axis-symmetric circular pattern. A two-part theoretical approach has been utilised coupling the thermodynamic concepts with the mechanics concepts. Thermodynamic concepts involve corrosive species transportation through micro-cracks under increasing compression, eventually causing blistering, while fracture mechanics concepts are used to treat the blister growth as a circular defect propagation. The influences of moduli ratio, thickness ratio, thermal mismatch ratio, poisson's ratio and interface roughness on blister growth are discussed. Experiment is reported for blistering to allow visualisation of interface and to permit coupled (diffusion and residual) stresses in the coating over a full range of interest. The predictions from model show excellent, quantitative agreement with the experimental results. (C) 2016 Elsevier Ltd. All rights reserved.