Stress Induced Fracture Transition in High-Temperature 9% Cr–CrMoV Dissimilar Welded Joint
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The creep behavior and microstructure of 9% Cr–CrMoV dissimilar welded joints were investigated in the present study. The results showed that the fracture occurred in the CrMoV-HAZ under 150 MPa at 839 K with necking, yet transformed to the fusion line under 120 MPa without obvious necking. The life of the sample ruptured under 150 MPa was 2512 h, while the sample ruptured under 120 MPa was 8041 h. The microhardness of the base metal of 9% Cr was ~275 HV, and the zone adjacent to the fusion line exhibited the highest hardness value (~320 HV). Numerous voids formed at the grain boundaries during the stress rupture test. The second particles at the grain boundaries acted as the initiation sites of the voids. In summary, the precipitation and coarsening of the second phase particles on grain boundaries were deemed as the crucial factors to result in this fracture mode transition.
KeywordsFracture transition Stress rupture Dissimilar welded joint Initiation site second phase particles
The authors gratefully acknowledge the National Natural Science Foundation of China (Grant no. U1760102), the financial support by the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, and Shanghai Science and Technology Committee (Grant no. 13DZ1101502).
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