GOALI: Crack Repair of Irradiated Stainless Steel by Friction Stir Processing

GOALI：通过搅拌摩擦加工修复辐照不锈钢裂纹

• 批准号: 1405508
• 负责人: Michael Miles
• 金额: $ 30万
• 依托单位: Brigham Young University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1405508&HistoricalAwards=false
• 关键词: GOALI; Crack; Repair; Irradiated; Stainless

This Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research to uncover the mechanisms of sigma phase and chromium carbide formation in friction stir processed austenitic stainless steel. An Eulerian finite element approach will be used to predict temperatures, strains, and strains rates in the stir zone so that fraction recrystallization can be predicted for different tool speeds and feed rates. The modeling work will be combined with experiments to test the hypothesis that sigma phase and chromium carbide formation can be minimized or eliminated when friction stir processing is done under conditions that avoid dynamic recrystallization. Phase identification will be performed on processed specimens by electron backscatter diffraction and by transmission electron microscopy for model validation. Hot cell experiments on irradiated stainless steel will test a second hypothesis that friction stir processing can be done without causing helium cracking in the heat affected zone of the stirred region. This research will provide fundamental understanding of the role of recrystallization on sigma phase and chromium carbide formation in friction stir processed austenitic stainless steel. A new approach for repairing stress corrosion cracks in nuclear components will emerge from the fundamental research results. As current fusion welding processes cause helium cracking during repair of components that have been irradiated for twenty or more years, this new approach has the potential of overcoming a major technical challenge in maintaining our fleet of aging reactors, which is critical to the national energy infrastructure and the economy. Additional societal benefits include the education of students who will be prepared to contribute to the nuclear industry, and an outreach program working with high school teachers on new curriculum development, aimed at encouraging female students to pursue careers in science and engineering.

该学术与工业联络机会 (GOALI) 奖项支持基础研究，以揭示搅拌摩擦加工奥氏体不锈钢中西格玛相和碳化铬形成的机制。欧拉有限元方法将用于预测搅拌区的温度、应变和应变速率，以便可以预测不同工具速度和进给速率的分数再结晶。建模工作将与实验相结合，以检验以下假设：当在避免动态再结晶的条件下进行搅拌摩擦加工时，可以最大限度地减少或消除西格玛相和碳化铬的形成。将通过电子背散射衍射和透射电子显微镜对处理后的样品进行相鉴定，以进行模型验证。辐照不锈钢的热室实验将检验第二个假设，即搅拌摩擦加工可以在搅拌区域的热影响区不引起氦裂纹的情况下进行。这项研究将为搅拌摩擦加工奥氏体不锈钢中再结晶对西格玛相和碳化铬形成的作用提供基础了解。基础研究成果将出现一种修复核部件应力腐蚀裂纹的新方法。 由于当前的熔焊工艺在修复已辐照二十年或更长时间的部件时会导致氦气裂纹，因此这种新方法有可能克服维护老化反应堆群的重大技术挑战，这对国家能源基础设施至关重要和经济。其他社会效益包括教育准备为核工业做出贡献的学生，以及与高中教师合作开发新课程的外展计划，旨在鼓励女学生从事科学和工程职业。