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.

这一学术联系机会奖(GOALI)支持基础研究，以揭示搅拌摩擦处理奥氏体不锈钢中Sigma相和碳化铬形成的机制。将使用欧拉有限元方法来预测搅拌区的温度、应变和应变率，从而可以预测不同刀具速度和进给速度下的分数再结晶。建模工作将与实验相结合，以验证在避免动态再结晶的条件下进行搅拌摩擦处理可以最大限度地减少或消除Sigma相和碳化铬形成的假设。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物相鉴定，以验证模型的有效性。对辐照不锈钢进行的热室实验将检验第二个假设，即可以在搅拌区域的热影响区进行摩擦搅拌处理，而不会导致氦破裂。本研究将对搅拌摩擦处理奥氏体不锈钢中再结晶对Sigma相和碳化铬形成的影响提供基础性的认识。基础性研究成果将为修复核构件应力腐蚀裂纹开辟新的途径。由于当前的熔化焊接工艺会在修复辐照了20年或更长时间的部件时导致氦气破裂，这种新方法有可能克服在维护我们的老化反应堆机队方面的重大技术挑战，这对国家能源基础设施和经济至关重要。其他社会福利包括对准备为核工业做出贡献的学生的教育，以及一个与高中教师合作开发新课程的外联计划，旨在鼓励女学生从事科学和工程职业。