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Investigation on the weakest zone in toughness of 9Cr/NiCrMoV dissimilar welded joint and its enhancement

Published online by Cambridge University Press:  13 June 2017

Xia Liu ,
Zhipeng Cai ,
Xionglin Deng  and
Fenggui Lu
Xia Liu
Affiliation:
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People’s Republic of China
Zhipeng Cai*
Affiliation:
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, People’s Republic of China
Xionglin Deng
Affiliation:
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
Fenggui Lu*
Affiliation:
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
*
a)Address all correspondence to these authors. e-mail: czpdme@mail.tsinghua.edu.cn
b)e-mail: Lfg119@sjtu.edu.cn
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Abstract

The impact toughness and related microstructure of the dissimilar 9Cr/NiCrMoV welded joint fabricated by narrow-gap submerged arc welding were systematically investigated in the paper. Results indicated that the fracture appearance transition temperature (50% FATT) for weld metal was −11 °C, while low and scattered absorbed energies determined by different crack growth paths for the heat affected zone of 9Cr were gained which could not satisfy the requirement of service. However, a dramatically enhanced impact toughness was obtained by optimizing the post-weld heat treatment (PWHT) process. Microstructure characterization revealed that the microstructure evolution from martensitic laths in the previous PWHT metals to a softer ferrite matrix with the supersaturated carbon precipitating from the matrix led to higher toughness in the optimized PWHT materials. In addition, the observation of the fracture morphology found that the fractography varied from brittle fracture to a fracture mode with both brittle and ductile fracture feature with the change of crack growth paths in 9Cr-HAZ.

Keywords

the weakest zone in toughnessdissimilar welded jointoptimized PWHTdramatically enhancementmicrostructure evolution
Type
Articles
Information
Journal of Materials Research , Volume 32 , Issue 16 , 28 August 2017 , pp. 3117 - 3127
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Copyright
Copyright © Materials Research Society 2017 

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Footnotes

Contributing Editor: Jürgen Eckert

References

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