Session: MF-16-02 Creep and Creep-Fatigue Interaction-2

Paper Number: 123166

123166 - Microstructural Evolution and Creep Behavior of T92/hr3c Dissimilar Welds Used in China Plants 

   Dissimilar metal welds between T92 ferritic steels and HR3C austenitic alloys are commonly used in ultra-supcritical power plants in China. Premature failure of such dissimilar welds can occur, resulting in unplanned plant outages that can cause huge economic losses. Most researches focus on the creep test of dissimilar welded joint in the laboratory. There is little research on the creep behavior of T92/HR3C welded joints used for a long time in practical power plants.

   In this article, microstructural evolution and creep behavior of T92/HR3C dissimilar welds after long-term service were studied involving in optical microscope, SEM, EBSD. The results show, the creep failure occurs in the fine-grained heat affected zone (FGHAZ) on T92 side. In this zone, the grain size of the fracture area increases, the number of subgrains decreases and the dislocation density decreases. With the increase of creep time, the particle size of Laves phase in the FGHAZ on T92 side gradually increases, M₂₃C₆ phase coarsens rapidly. At the same time, the martensite lath degenerates and the cavities size increases. The hardness distribution also shows that the fine-grained heat affected zone of T92 after creep has the lowest hardness in the whole welded joint. These microstructure degredation directly lead to the decrease of creep strength in FGHAZ.

Presenting Author: Chang Che China Special Equipment Inspection And Research Institute

Presenting Author Biography: Dr CHE CHANG, received doctorate in materials science from Beihang University in 2005, then became a post-doctoral scholar in the department of thermal engineering, Tsinghua University. Now she works as a senior engineer in China Special Equipment Inspection & Research Institute, academic leader of in safety evaluation of power station boilers. Research field focuses on high temperature properties of advanced heat-resistant steels and superalloys, microstructural evolution during high-temperature service, phenomenological understanding of creep and fracture processes, as well as failure analysis and life prediction of boiler materials.

Authors:

Chang Che China Special Equipment Inspection And Research Institute
Yu Cong University of Science and Technology Beijing
Jianming Yu China Special Equipment Inspection And Research Institute
Xinzhong Chen China Special Equipment Inspection And Research Institute
Hao Wang University of Science and Technology Beijing