Kinetics Analysis of Thermally Activated Elementary Processes in Stress Corrosion Cracking Crack Growth

为了弄清结构材料在轻水反应堆环境中应力腐蚀开裂的热激活元素过程，测量了稳态裂纹扩展速率，并计算了表观激活能。基于应力腐蚀裂纹扩展的多个速率决定过程，分析了观测到的表观激活能。对奥氏体合金及其焊缝金属裂纹扩展速率随温度变化的几种类型进行了分类。讨论了定义和测量表观活化能的不同方法。对于镍基合金及其焊缝金属在模拟压水堆环境中的裂纹扩展，其表观激活能较高，接近于正常氧化过程的表观激活能。敏化304不锈钢在含氧高温纯水环境中的裂纹扩展速率随温度的升高而单调增加。另一方面，a p…在含有化学添加剂或杂质的高温水中，裂纹扩展速率随温度变化的峰值较大。表观活化能取决于试验条件。应变硬化低碳不锈钢在纯水中的应力腐蚀裂纹扩展速率在200~288℃范围内随温度单调增加，表明裂纹扩展主要受热激活过程控制。表观激活能在不同的温度范围内不同，这可能与温度对参与裂尖氧化动力学的多元过程的影响有关。所有试件在升温或降温后都观察到了时滞裂纹扩展周期。考虑到温度对参与裂纹尖端氧化动力学的多元素过程的影响，分析了温度、外加载荷和材料强度对表观激活能的影响。较少

In order to clarify the thermal activated element processes involved in stress corrosion cracking of structural materials in light water reactor environments, steady state crack growth rates were measured and the apparent activation energies were evaluated. The observed apparent activation energies are analyzed based on multiple rate-determining processes involved in stress corrosion crack growth. Several types o f temperature-dependence for crack growth rates of austenitic alloys and their weld metals are classified. Different ways of defining and measuring apparent activation energy are discussed. For the crack growth of Ni-based alloys and their weld metals in simulated pressurized water reactor environments, the apparent activation energy is relatively high and close to those for normal oxidation processes. The crack growth rates of sensitized 304 stainless steels in oxygenated high temperature pure water environments increased monotonically with temperature. On the other hand, a p … More eak in crack growth rate versus temperature was observed in high temperature water containing chemical additions or impurities. The apparent activation energy depends on testing conditions. The stress corrosion cracking growth rates for strain-hardened low-carbon stainless steels in pure water increase monotonically with temperature in the range 200-288°C, which show that crack growth is mainly controlled by thermally-activated processes. The apparent activation energies are different in different temperature ranges, and could be related to the effects of temperature on multiple-element processes that are involved in the crack-tip oxidation kinetics. Time-lag crack growth periods after increasing or decreasing the temperature were observed in all the tested specimens. The effects of temperature, applied loading and material strength on apparent activation energy are analyzed by taking into consideration the effects of temperature on the multiple element processes involved in the crack tip oxidation kinetics. Less