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首页> 外文会议>12th International Conference on Environmental Degradation of Materials in Nuclear Power Systems: Water Reactors 2005 vol.2 >THE MECHANISM AND MODELING OF INTERGRANULAR STRESS CORROSION CRACKING OF NICKEL-CHROMIUM-IRON ALLOYS EXPOSED TO HIGH PURITY WATER
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THE MECHANISM AND MODELING OF INTERGRANULAR STRESS CORROSION CRACKING OF NICKEL-CHROMIUM-IRON ALLOYS EXPOSED TO HIGH PURITY WATER

机译：高纯水中镍铬铁合金晶间应力腐蚀开裂的机理与模型

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This investigation combines microstructural characterization, fracture mechanics analyses, atomistic modeling, and experimental crack growth rate data to better elucidate the mechanism of stress corrosion cracking of nickel-based alloys exposed to high temperature, high purity deaerated water. Additionally, this paper develops a mechanistically based equation that is suggested to be generally applicable to SCC of Alloy 600-type alloys exposed to high purity water. Results show that stress corrosion crack tips are truly intergranular, sharp (～5-10 nm crack tip openings), and are well described by moving crack fracture mechanics. These findings, combined with the clear dependency of the crack growth rate on the electrochemical potential and the constancy of the apparent activation energy (see Morton's paper in these proceedings) suggest that the stress corrosion crack growth rate in high purity water is governed by the supply rate of an embrittling species to the crack tip process zone and by the tearing resistance of the material immediately in front of the crack tip (I.e. the local J-R curve). Consideration of both hydrogen and oxygen embrittlement show that both mechanisms are feasible, although there is somewhat more support for a hydrogen mechanism. An example of the crack growth rate model and data fitting procedures are given for Alloy 600 heat affected zone (HAZ) material. Results show that the fitting procedure can have a large effect on model parameters and subsequent extrapolations. For the data considered, nonlinear curve fitting in real space (vice log space) resulted in the most accurate fit. The Alloy 600 HAZ modeling shows that the apparent activation energy for crack growth is lower than is typically reported (91.2 kJ/mol ± 27.4|_(95%) kJ/mol vice ～130 kJ/mol), the crack growth rate is weakly dependent on the applied stress intensity factor (SCCGR ∝ K~1), and the effect of electrochemical potential is significant (～3.6X near Ni/NiO).
机译：这项研究结合了微观结构表征，断裂力学分析，原子模型和实验裂纹扩展速率数据，以更好地阐明暴露于高温，高纯度脱气水的镍基合金的应力腐蚀开裂机理。此外，本文提出了一种基于机械的方程式，该方程式通常适用于暴露于高纯水的合金600型合金的SCC。结果表明，应力腐蚀裂纹尖端确实是晶间的，尖锐的（约5-10 nm裂纹尖端开口），并且通过移动裂纹断裂力学得到了很好的描述。这些发现，再加上裂纹扩展速率对电化学势和表观活化能的恒定性的明确依赖性（请参阅这些程序中的莫顿论文）表明，高纯水中的应力腐蚀裂纹扩展速率受供水的控制。脆性物质到达裂纹尖端加工区的速率以及裂纹尖端之前材料的抗撕裂性（即局部JR曲线）。对氢和氧脆化的考虑都表明这两种机理都是可行的，尽管对氢机理有更多的支持。给出了合金600热影响区（HAZ）材料的裂纹扩展速率模型和数据拟合程序的示例。结果表明，拟合过程对模型参数和随后的外推影响很大。对于所考虑的数据，实际空间（副测井空间）中的非线性曲线拟合导致最准确的拟合。 Alloy 600 HAZ模型表明，裂纹扩展的表观活化能比通常报道的要低（91.2 kJ / mol±27.4 | _（95％）kJ / mol副〜130 kJ / mol），裂纹扩展速率较弱取决于施加的应力强度因子（SCCGR ∝ K〜1），电化学势的影响很明显（Ni / NiO附近为〜3.6倍）。

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