Transition and fracture shift behavior in LCF test of dissimilar welded joint at elevated temperature
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2018年第4期
论文作者：Xiongfei Wang Chendong Shao Xia Liu Fenggui Lu
文章页码：720 - 731
摘 要：This work focused on the low-cycle fatigue（LCF） behavior of modified 9Cr/CrMoV dissimilar welded joint at elevated temperature. Narrow gap submerged arc welding（NG-SAW） process via multi-pass and multi-layer techniques was employed to fabricate the welded joint. LCF tests at different strain amplitude range from 0.22% to 0.75% were performed at strain ratio R =-1. The two-slope behavior based on fracture location shift was presented both on the cyclic stress-strain（CSS） curve and Manson-Coffin（M-C） curve, which could be applied to predict the fatigue life more precisely especially at relatively low strain amplitude. The results indicated that the joint failed in CrMoV-base metal（BM） at relatively low strain amplitude below 0.4% while failure shifted to CrMoV-over tempered zone（OTZ） at higher strain amplitude above 0.4%. Fatigue failure occurred in CrMoV-BM at low strain amplitude could be attributed to temperature softening effect in CrMoV-BM combined with cyclic strengthening in CrMoV-OTZ. While CrMoV-OTZ with a comparable number of grain boundaries and much lower hardness than that of CrMoV-BM was deemed to be the weakest zone across the welded joint at higher strain amplitude.EBSD investigations also revealed that CrMoV-BM experienced more fatigue damage at relatively low strain amplitude, while CrMoV-OTZ accumulated more plastic strain at higher strain amplitude.
Xiongfei Wang1，Chendong Shao1，Xia Liu2，Fenggui Lu1
1. Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University2. Shanghai Turbine Plant of Shanghai Electric Power Generation Equipment Co.Ltd.
摘 要：This work focused on the low-cycle fatigue（LCF） behavior of modified 9Cr/CrMoV dissimilar welded joint at elevated temperature. Narrow gap submerged arc welding（NG-SAW） process via multi-pass and multi-layer techniques was employed to fabricate the welded joint. LCF tests at different strain amplitude range from 0.22% to 0.75% were performed at strain ratio R =-1. The two-slope behavior based on fracture location shift was presented both on the cyclic stress-strain（CSS） curve and Manson-Coffin（M-C） curve, which could be applied to predict the fatigue life more precisely especially at relatively low strain amplitude. The results indicated that the joint failed in CrMoV-base metal（BM） at relatively low strain amplitude below 0.4% while failure shifted to CrMoV-over tempered zone（OTZ） at higher strain amplitude above 0.4%. Fatigue failure occurred in CrMoV-BM at low strain amplitude could be attributed to temperature softening effect in CrMoV-BM combined with cyclic strengthening in CrMoV-OTZ. While CrMoV-OTZ with a comparable number of grain boundaries and much lower hardness than that of CrMoV-BM was deemed to be the weakest zone across the welded joint at higher strain amplitude.EBSD investigations also revealed that CrMoV-BM experienced more fatigue damage at relatively low strain amplitude, while CrMoV-OTZ accumulated more plastic strain at higher strain amplitude.
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