Investigation of microstructural evolution and creep rupture behaviour of 9% Cr MarBN steel welds

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:791

Article

Xu, X.¹  Benaarbia, A.²  Allen, D. J.¹  Jepson, M. A. E.¹  Sun, W.³ 

[1] Loughborough Univ, Dept Mat, Loughborough LE11 3TU, Leics, England

[2] Univ Lorraine, Arts & Metiers Inst Technol, LEM3, CNRS, F-57000 Metz, France

[3] Univ Nottingham, Dept Mech Mat & Mfg Engn, Nottingham NG7 2RD, Notts, England

关键词: 9% Cr Tempered martensitic steel;    Heat affected zone;    Multi-pass welding;    High temperature creep;    Failure mechanism;   

DOI  :  10.1016/j.msea.2020.139546

来源: Elsevier

【 摘 要 】

The weldments made from the 9-12% Cr tempered martensitic steel are associated with a complex micro-structure arising from complicated thermal histories of the fusion and heat affected zones. The complicated microstructural and micro-mechanical states in these critical regions provide a challenge for the determination of creep failure mechanisms. Based on detailed metallographic examination, the microstructural distribution in the heat affected zone of the welds constructed using a recently developed 9% Cr MarBN steel, IBN-1, has been identified and classified into Equiaxed Zone (EZ), Duplex Zone (DZ) and Over-tempered Zone (OZ). Cross-weld testing performed at 650 degrees C has revealed a significant reduction in creep life as compared to bulk material. Creep rupture has been shown to occur in the parent metal region with a ductile manner at a high stress, whereas creep rupture initiates in the DZ region in an intergranular manner at a low stress. Detailed metallographic investigation has further revealed a higher damage susceptibility in the regions along the pre-existing Prior Austenite Grain Boundaries (PAGBs). The diffusional reaustenitisation of local microstructure along the PAGBs leads to a lower strength of matrix in combination with a lack of intergranular precipitates as compared to the surrounding microstructure formed after displacive reaustenitisation.

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