高溫純水中82合金與304低碳不銹鋼異材銲件之應力腐蝕研究

An Investigation into Stress Corrosion Cracking of Dissimilar Metal Welds of 304L Stainless Steel and Alloy 82 in High Temperature Pure Water

黃冠儒(G. R. Huang) ； 葉宗洸(T. K. Yeh) ； 蔡春鴻(C. H. Tsai)

《防蝕工程》 23卷3期 (2009/09) Pp. 213-226

https://doi.org/10.6376/JCCE.200909.0213

摘要

近年來，許多商用輕水式反應器(Light Water Reactor, LWR)的結構組件陸續出現異材金屬銲件的應力腐蝕龜裂(Stress Corrosion Cracking, SCC)問題，世界各國的研發機構也因此投入相當大的人力進行相關議題的研究。國內電廠結構組件上銲件所使用沃斯田不銹鋼（304與304L）與82合金，亦非常可能面臨類似的SCC問題，因此值得在模擬國內核一、二廠水化學環境中，針對此類銲件進行殘留應力與SCC分析研究。本研究主要探討沃斯田系304L不銹鋼與鎳基合金Alloy 82異材銲件之應力腐蝕龜裂敏感性(Susceptibility)及腐蝕抑制技術。銲件經熱敏化處理(Thermal sensitization treatment)、珠擊(Shot peening)處理、固溶退火(Solution annealing)處理與表面研磨(Surface polishing)，分別對於防治應力腐蝕效益的測試評估比較。經由慢應變速率拉伸實驗結果得知，實驗試樣82合金與304低碳不銹鋼異材銲件不易產生沿晶SCC的破裂型態。另外也得知，經由(650℃/24hrs)熱敏化處理的試樣抑制SCC效果不佳，而珠擊處理與固溶退火處理的抑制SCC效果不錯。珠擊處理明顯使試樣強度提升，固溶退火則是明顯使試樣伸長量提升。經由本實驗結果得知，欲加強異材銲接組件抵抗應力腐蝕的能力，珠擊處理或固溶退火處理將是相對有效的選擇。

關鍵字

輕水式反應器 ； 異材金屬焊件 ； 應力腐蝕龜裂 ； 殘留應力

並列摘要

Structural components with dissimilar metal welds in commercial light water reactors have been increasingly experiencing stress corrosion cracking (SCC) in recent years. A great deal of efforts have been devoted to research on the mechanisms and countermeasures of this problem worldwide. Austenitic stainless steels (SS) such as Type 304 SS and Type 304L SS coupled with alloy 82 are extensively used in the structural components of domestic nuclear power plants and are therefore susceptible to similar SCC problems. Accordingly, it is worth looking into the residual stress and SCC behavior of dissimilar metal welds of the foregoing two types of alloys in simulated reactor water environments. In the current study, SCC susceptibility and corrosion mitigation techniques for dissimilar metal welds of austenitic 304L SS and nickel-based alloy 82 were investigated. Test samples with welds were prepared under various conditions of thermal sensitization treatment, shot peening, solution annealing, and surface polishing and then underwent destructive corrosion tests. According to the results from slow strain rate tensile tests, dissimilar metal welds of 304L SS and alloy 82 did not show any significant intergranular SCC. Among all test samples, the one that was thermally sensitized at 650 ℃ for 24 hr exhibited the highest susceptibility to SCC. On the other hand, the one that underwent shot peening or was solution annealed showed no sign of SCC. It was also found that the shot peening process enhanced the strength of the sample, and the solution annealing process induced a greater elongation of the sample. For a better resistance to SCC, the processes of shot peening and solution annealing would be relatively effective choices.

並列關鍵字

Light Water Reactor ； Dissimilar metal weld ； Stress Corrosion Cracking ； Residual stress