1 Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China 2 Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084, China 3 State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China 4 Collaborative Innovation Center of Advanced Nuclear Energy Technology, Tsinghua University, Beijing 100084, China 5 China Datang Corporation Science and Technological Research Institute, Thermal Power Technology Research Institute, Beijing 100040, China
Oxidation damage and interfacial failure of dissimilar metal welds containing ferritic heat resistant steels
1 Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China 2 Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084, China 3 State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China 4 Collaborative Innovation Center of Advanced Nuclear Energy Technology, Tsinghua University, Beijing 100084, China 5 China Datang Corporation Science and Technological Research Institute, Thermal Power Technology Research Institute, Beijing 100040, China
摘要 The ex-service steam tubes containing dissimilar metal weld (DMW) between high Cr ferritic steel T91 and austenitic stainless steel TP347H and the ex-service steam tubes containing DMW between low Cr ferritic steel G102 and austenitic stainless steel TP347H were obtained from coal-fired thermal power plants in China, and their microstructures at the nickel-based weld metal (WM)/ferritic steel interfaces and oxidation characteristics were investigated. After operating for 15,000 h at steam temperature of 541 C and steam pressure of 17.5 MPa, a G102/TP347H DMW failed along the WM/ G102 steel interface, which was a dangerous premature failure mode without obvious plastic deformation. This interfacial failure was attributed to the interaction between oxidation and cracking along the interface, where fracture appeared to be related with the strain concentration at the interface. Oxide notch along the WM/G102 steel interface was the precursor of premature interfacial failure of DMW involving G102. For the DMW involving high Cr ferritic steel T91, ferritic steel side could form a Cr-rich passive film during service and thus would not be further oxidized after operating for 67,000 h at steam temperature of 541 C and steam pressure of 3.5 MPa. It was concluded that oxidation played a more important role in failure of these DMWs, and retarding the development of oxidation and avoiding the interfacial oxide notch would dramatically improve the service performance of steam tubes containing DMWs.
Abstract：The ex-service steam tubes containing dissimilar metal weld (DMW) between high Cr ferritic steel T91 and austenitic stainless steel TP347H and the ex-service steam tubes containing DMW between low Cr ferritic steel G102 and austenitic stainless steel TP347H were obtained from coal-fired thermal power plants in China, and their microstructures at the nickel-based weld metal (WM)/ferritic steel interfaces and oxidation characteristics were investigated. After operating for 15,000 h at steam temperature of 541 C and steam pressure of 17.5 MPa, a G102/TP347H DMW failed along the WM/ G102 steel interface, which was a dangerous premature failure mode without obvious plastic deformation. This interfacial failure was attributed to the interaction between oxidation and cracking along the interface, where fracture appeared to be related with the strain concentration at the interface. Oxide notch along the WM/G102 steel interface was the precursor of premature interfacial failure of DMW involving G102. For the DMW involving high Cr ferritic steel T91, ferritic steel side could form a Cr-rich passive film during service and thus would not be further oxidized after operating for 67,000 h at steam temperature of 541 C and steam pressure of 3.5 MPa. It was concluded that oxidation played a more important role in failure of these DMWs, and retarding the development of oxidation and avoiding the interfacial oxide notch would dramatically improve the service performance of steam tubes containing DMWs.
Xiao-gang Li,Zhi-peng Cai,Xin Chen, et al. Oxidation damage and interfacial failure of dissimilar metal welds containing ferritic heat resistant steels[J]. Journal of Iron and Steel Research International, 2021, 28(11): 1439-1450.
2021, Vol. 28 
