Quantifying cracking and strain localisation in a cold spray chromium coating on a zirconium alloy substrate under tensile loading at room temperature
Quantifying cracking and strain localisation in a cold spray chromium coating on a zirconium alloy substrate under tensile loading at room temperature
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DOI：
10.1016/j.jnucmat.2024.154899
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发表时间：
2024-01
影响因子：
3.1
通讯作者：
Ioannis Alakiozidis;Callum Hunt;R. Thomas;D. Lunt;Albert D. Smith;Mia Maric;Zaheen Shah;A. Ambard;Philipp Frankel
中科院分区：
文献类型：
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作者：
Ioannis Alakiozidis;Callum Hunt;R. Thomas;D. Lunt;Albert D. Smith;Mia Maric;Zaheen Shah;A. Ambard;Philipp Frankel
采用冷喷涂（CS）技术在优化的ZIRLO TM基体上制备了Cr涂层，并通过原位扫描电子显微镜（SEM）对涂层进行了室温拉伸试验，研究了涂层的力学性能和开裂行为。为了实现这一点，弯曲的微拉伸样品从包层管加工，并在涂层表面上施加苯乙烯辅助的金重塑图案。通过自动化SEM图像处理对施加轴向应变的涂层的宏观裂纹密度进行量化，同时用高分辨率数字图像相关（HRDIC）监测应变的局部化。与大多数沉积在韧性基底上的脆性薄膜一样，在施加的外部应力下，平行裂纹通道出现在涂层表面上，垂直于加载方向。在0.5%轴向应变下捕获第一裂纹，而在1.5%时观察到饱和。发现涂层中的单裂纹形成导致局部应变松弛并向未开裂段的中点重新分布。涂层的局部断裂应变随裂纹间距的减小而增大，而涂层表面在与加载方向成35°和145°角处出现剪切带，这是塑性变形的证据。弯曲样品几何形状的裂纹密度与管使用修改后的剪切滞后模型，考虑通过X射线衍射（XRD）测量的涂层中的残余应力。CS Cr涂层显示出高水平的结合和与基材的机械互锁，即使在3%的轴向应变。
The mechanical and cracking behaviour of a Cr coating, deposited on an Optimized ZIRLO T M substrate using the Cold Spraying (CS) technique, was investigated by in-situ scanning electron microscopy (SEM) tensile testing at room temperature. To achieve this, curved micro-tensile samples were machined from cladding tubes, and a styrene-assisted gold remodelled pattern was applied on the coating surface. The macroscopic crack density of the coating with applied axial strain was quantified through automated SEM image processing, whilst the localisation of strain was monitored with High Resolution Digital Image Correlation (HRDIC). Like with most brittle thin films deposited on ductile substrates, under applied external stress, parallel crack channelling appeared on the coating surface, perpendicular to the loading direction. The first crack was captured at 0.5% axial strain, whilst saturation was observed at 1.5%. Single crack formation in the coating was found to cause relaxation of local strains and redistribution towards the uncracked segment's midpoint. The local fracture strain of the coating was found to increase with the decreasing crack spacing, whilst shear bands appeared on the coating's surface at 35° and 145° with respect to the loading direction, which is evidence of plastic deformation. The crack density of the curved sample geometry was correlated with the tubes using a modified shear-lag model, considering the residual stresses in the coating measured by X-ray Diffraction (XRD). The CS Cr coating showed high levels of bonding and mechanical interlocking with the substrate, even after 3% axial strain.