Examination of Variable Frequency Drive Transformer Copper Cooling Line Failures from Nuclear Power Plants

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• 作者：Andrew Ruminski
• 关键词：Intergranular cracking ; Fatigue cracking ; Scanning electron microscope ; Metallography ; Microhardness ; Copper ; Failure analysis
• 刊名：Journal of Failure Analysis and Prevention
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：16
• 期：2
• 页码：310-315
• 全文大小：2,222 KB
• 参考文献：1.M. Stevenson, M. Barkey, J. McDougall, Stresses in bent copper tubing: application to fatigue and stress-corrosion cracking failure mechanisms. J. Fail. Anal. Prev. 5, 25–29 (2005)CrossRef
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  6.Y. Yagodzinskyy, E. Malitckii, T. Saukkonem, H. Hänninen, Hydrogen-enhanced creep and cracking of oxygen-free phosphorus-doped copper. Scr. Mater. 67, 931–934 (2012)CrossRef
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• 作者单位：Andrew Ruminski (1)
  
  1. Westinghouse Electric Company - Materials Center of Excellence, 1332 Beulah Road, Pittsburgh, PA, 15235, USA
  
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Materials Science
  Tribology, Corrosion and Coatings
  Characterization and Evaluation Materials
  Mechanics
  Structural Mechanics
  Quality Control, Reliability, Safety and Risk
  
• 出版者：Springer Boston
• ISSN：1864-1245

文摘

The findings from a failure examination on copper cooling lines from nuclear power plant transformer cooling systems are discussed in this article. The failures occurred prior to regular service at two different nuclear power plants during installation and qualification testing. A failure examination including—light optical microscopy, scanning electron microscopy, metallography, and microhardness—was conducted on the fractured lines. The fractures predominately had fatigue striation morphologies, but were found to have initiated in areas exhibiting intergranular cracking, secondary cracking, and surface pitting. Additionally, evidence of phosphorus rich particles was found in the IG crack regions. The failures are hypothesized to be the result of outside diameter environmentally initiated cracking, assisted by residual stresses from brazing, and propagated by fatigue.