Investigation of Early Cracking of Dissimilar Metal Welds in a 1000-MW Ultra-supercritical Power Plant Close to the Sea
- 20 Downloads
The early cracking of dissimilar metal welds (DMWs) between T91 martensitic steel and austenitic steel in a 1000-MW ultra-supercritical power plant was investigated in this article. Optical microscopy and scanning electron microscopy were used to characterize the microstructures of DMWs. The result shows that the breakdown of DMWs was brittle rupture along the prior austenite crystal boundary. The crack extended from T91 heat-affected zone to T91 base metal. Compared with the spare DMWs, its tensile strength and bending properties met the standard for DMWs. Hardness of T91 HAZ from failed DMWs was much higher than that of spare DMWs. Some pitting was observed at the T91 HAZ. Associating the high hardness of DMWs and particular service environment, it is concluded that the failure of DMWs was caused by the stress-corrosion crack.
KeywordsDissimilar metal welds Post-weld heat treatment Brittle rupture
This work is supported by the National Natural Science Foundation of China (51806166), the Innovative Talents Support Plan of China Postdoctoral Foundation (BX2019269) and the Fundamental Research Funds for the Central Universities (xjj2018064). We would like to thank anonymous reviewers for their helpful comments and suggestions in improving the paper.