Characteristics of premature creep failure in over-tempered base metal of grade 91 steel weldment

Yiyu Wang; Wei Zhang; Yanli Wang; Zhili Feng

doi:10.1016/j.ijpvp.2021.104396

Characteristics of premature creep failure in over-tempered base metal of grade 91 steel weldment

Yiyu Wang, Wei Zhang, Yanli Wang, Zhili Feng

Research output: Contribution to journal › Article › peer-review

8 Scopus citations

Abstract

In this work, characteristics of premature creep failure in the over-tempered base metal (OT-BM) of a Grade 91 steel weldment are investigated with specially designed creep experiments and advanced microstructure characterization. In situ digital image correlation (DIC) strain measurements reveal that local creep strain as high as 100% accumulated in the OT-BM, compared with only 10% nominal strain over the gauge length. The creep strain rate in the OT-BM is identical to that in the intercritical heat-affected zone and fine-grained heat-affected zone at the secondary creep stage and early tertiary stage, but faster at the late tertiary stage. Microstructural analysis shows that highly recovered microstructure in the OT-BM leads to the lowest hardness, the largest grain size, the lowest fraction of coincidence site lattice boundaries, and the lowest localized strain energy. Dislocation creep and transgranular creep fracture are the dominant deformation and fracture mechanisms in the OT-BM under the current creep testing condition of a low temperature (550 °C) and a high stress (215 MPa).

Original language	English
Article number	104396
Journal	International Journal of Pressure Vessels and Piping
Volume	192
DOIs	https://doi.org/10.1016/j.ijpvp.2021.104396
State	Published - Aug 2021

Funding

Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Preprint submitted to International Journal of Pressure Vessels and Piping September 14, 2020. This work is funded by a Department of Energy R&D Award ( FWP-FEAA118 ). The research and development work were performed at Oak Ridge National Laboratory, which is managed by UT-Battelle LLC for the US Department of Energy under contract DE-AC05-00OR22725 . The authors would like to thank Mr. Doug Kyle for his assistance in the creep testing experiments, and Dr. Wei Tang and Dr. Xiang Chen for their discussion and review.

Funders	Funder number
U.S. Department of Energy	DE-AC05-00OR22725, FWP-FEAA118
Oak Ridge National Laboratory
UT-Battelle

Keywords

Creep strength
Digital image correlation
Grade 91 steel
Heat affected zone
Microstructure
Over-tempered base metal
Type IV Cracking

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10.1016/j.ijpvp.2021.104396

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title = "Characteristics of premature creep failure in over-tempered base metal of grade 91 steel weldment",

abstract = "In this work, characteristics of premature creep failure in the over-tempered base metal (OT-BM) of a Grade 91 steel weldment are investigated with specially designed creep experiments and advanced microstructure characterization. In situ digital image correlation (DIC) strain measurements reveal that local creep strain as high as 100% accumulated in the OT-BM, compared with only 10% nominal strain over the gauge length. The creep strain rate in the OT-BM is identical to that in the intercritical heat-affected zone and fine-grained heat-affected zone at the secondary creep stage and early tertiary stage, but faster at the late tertiary stage. Microstructural analysis shows that highly recovered microstructure in the OT-BM leads to the lowest hardness, the largest grain size, the lowest fraction of coincidence site lattice boundaries, and the lowest localized strain energy. Dislocation creep and transgranular creep fracture are the dominant deformation and fracture mechanisms in the OT-BM under the current creep testing condition of a low temperature (550 °C) and a high stress (215 MPa).",

keywords = "Creep strength, Digital image correlation, Grade 91 steel, Heat affected zone, Microstructure, Over-tempered base metal, Type IV Cracking",

author = "Yiyu Wang and Wei Zhang and Yanli Wang and Zhili Feng",

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year = "2021",

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doi = "10.1016/j.ijpvp.2021.104396",

language = "English",

volume = "192",

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AU - Wang, Yiyu

AU - Zhang, Wei

AU - Wang, Yanli

AU - Feng, Zhili

PY - 2021/8

Y1 - 2021/8

N2 - In this work, characteristics of premature creep failure in the over-tempered base metal (OT-BM) of a Grade 91 steel weldment are investigated with specially designed creep experiments and advanced microstructure characterization. In situ digital image correlation (DIC) strain measurements reveal that local creep strain as high as 100% accumulated in the OT-BM, compared with only 10% nominal strain over the gauge length. The creep strain rate in the OT-BM is identical to that in the intercritical heat-affected zone and fine-grained heat-affected zone at the secondary creep stage and early tertiary stage, but faster at the late tertiary stage. Microstructural analysis shows that highly recovered microstructure in the OT-BM leads to the lowest hardness, the largest grain size, the lowest fraction of coincidence site lattice boundaries, and the lowest localized strain energy. Dislocation creep and transgranular creep fracture are the dominant deformation and fracture mechanisms in the OT-BM under the current creep testing condition of a low temperature (550 °C) and a high stress (215 MPa).

AB - In this work, characteristics of premature creep failure in the over-tempered base metal (OT-BM) of a Grade 91 steel weldment are investigated with specially designed creep experiments and advanced microstructure characterization. In situ digital image correlation (DIC) strain measurements reveal that local creep strain as high as 100% accumulated in the OT-BM, compared with only 10% nominal strain over the gauge length. The creep strain rate in the OT-BM is identical to that in the intercritical heat-affected zone and fine-grained heat-affected zone at the secondary creep stage and early tertiary stage, but faster at the late tertiary stage. Microstructural analysis shows that highly recovered microstructure in the OT-BM leads to the lowest hardness, the largest grain size, the lowest fraction of coincidence site lattice boundaries, and the lowest localized strain energy. Dislocation creep and transgranular creep fracture are the dominant deformation and fracture mechanisms in the OT-BM under the current creep testing condition of a low temperature (550 °C) and a high stress (215 MPa).

KW - Creep strength

KW - Digital image correlation

KW - Grade 91 steel

KW - Heat affected zone

KW - Microstructure

KW - Over-tempered base metal

KW - Type IV Cracking

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ER -

Characteristics of premature creep failure in over-tempered base metal of grade 91 steel weldment

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