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Understanding and Mitigatin of Stress Corrosion Cracking of Reactor Vassel Materials in Oxidizing Supercritical Water Environments

氧化超临界水环境中反应堆容器材料应力腐蚀开裂的理解和缓解

基本信息

批准号：
13450290
负责人：
WATANABE Yutaka
金额：
$ 7.49万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Corrosion morphology and rates of various corrosion resistant alloys have been examined in simulated environments of supercritical water oxidation processes. Importance of physical property of water, in particular dielectric constant, to corrosion of metals in supercritical water have been demonstrated. It has been demonstrated that corrosion rate of metals in supercritical water is strongly dependent on applied pressure and can he uniquely arranged by dielectric constant of water including both supercritical state and sub-critical liquid phase.Scale oxides formed in supercritical water environments were in good agreement with thermodynamically predicted oxide. Corrosion rate was able to be correlated with types of the scale oxides.Slow strain rate tests have been performed in neutral to acidic supercritical water up to 550℃/6OMPa to evaluate stress corrosion cracking (SCC) behavior of alloys in supercritical water environments. Effects of applied pressure (water density or dielectric … More constant effect) and sulfuric acid have been demonstrated. For sensitized stainless steel -pure water system, effects of phase state of water and applied pressure, more essentially, physical property of water, were clearly observed. SCC did not occur in the oxygenated "gas-like" supercritical water at 400℃/25MPa. Cracking occurred at 400℃/30MPa and the cracking severity was more pronounced as applied pressure was increased up to 60MPa at the same temperature. The results gave a strong evidence of the "dissolution mechanism". In contrast, for non-sensitized stainless steel -sulfuric acid water system, severe cracking with IG occurred even in a "gas-like" supercritical water and dielectric constant did not affect cracking severity. The results would indicate "dissolution mechanism" is not very likely and might suggest "oxidation cracking".Importance of aging degradation in both mechanical properties and corrosion resistance in supercritical water environments has been pointed out.A new corrosion-inhibition method for supercritical water environments has been developed, where dependence of solubility of Cr oxides on temperature and dielectric constant of water is utilized. Less

研究了各种耐蚀合金在模拟超临界水氧化环境中的腐蚀形貌和腐蚀速率。水的物理性质，特别是介电常数，对金属在超临界水中的腐蚀的重要性已经被证明。研究表明，金属在超临界水中的腐蚀速率与压力密切相关，并且可以由水的介电常数（包括超临界状态和亚临界液相）唯一地决定，在超临界水环境中形成的氧化物与理论预测的氧化物相吻合。通过在中性至酸性的超临界水（550℃/60 MPa）中的慢应变速率试验，研究了合金在超临界水环境中的应力腐蚀开裂（SCC）行为。施加压力的影响（水密度或电介质 ...更多信息恒定效应）和硫酸。对于敏化不锈钢-纯水体系，可以清楚地观察到水的相态和压力，更重要的是水的物理性质的影响。在400℃/25 MPa的含氧“类气体”超临界水中没有发生应力腐蚀开裂。在400℃/30 MPa下发生开裂，在相同温度下，当施加的压力增加到60 MPa时，开裂的严重程度更明显。实验结果为“溶解机理”提供了有力的证据。相比之下，对于非敏化不锈钢-硫酸-水体系，即使在“气体状”超临界水中，IG也会发生严重的开裂，并且介电常数不影响开裂的严重性。结果表明，超临界水环境中Cr氧化物的溶解机理不太可能是“溶解机理”，而可能是“氧化开裂机理”;指出了超临界水环境中Cr氧化物的时效降解对力学性能和耐腐蚀性能的重要性;利用Cr氧化物的溶解度对温度和水的介电常数的依赖性，提出了一种新的超临界水环境缓蚀方法。少