Effect of machining on near surface microstructure and the observation of martensite at the fatigue crack tip in PWR environment of 304L stainless steel

Zaiqing Que; Caitlin Huotilainen; Tiia Seppänen; Jari Lydman; Ulla Ehrnstén

doi:10.1016/j.jnucmat.2021.153399

Effect of machining on near surface microstructure and the observation of martensite at the fatigue crack tip in PWR environment of 304L stainless steel

Zaiqing Que^*
, Caitlin Huotilainen
, Tiia Seppänen
, Jari Lydman
, Ulla Ehrnstén

^*Corresponding author for this work

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

18 Citations (Scopus)

180 Downloads (Pure)

Abstract

This work highlighted that a ground surface finish and the exposure to a pressurised water reactor (PWR) environment result in a decreased low-cycle fatigue lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 304 L austenitic stainless steel. A ground surface finish promotes fatigue crack initiation and short crack growth especially in a water environment, due to the highly deformed underlying microstructure with high-angle grain boundaries and the grinding marks on surface. Martensite was observed in the vicinity of secondary crack tips in specimens tested in a simulated PWR primary side environment. The aggregated presence of α′- and ε-martensite in the vicinity of the fatigue crack tip can enhance the material's susceptibility to hydrogen-assisted fatigue cracking. Martensite formation was rarely observed in specimens exposed to high temperature air. The phase transformation from γ-austenite to αꞌ-martensite in the PWR primary environment occurred via the intermediate ε-martensite phase.

Original language	English
Article number	153399
Journal	Journal of Nuclear Materials
Volume	558
DOIs	https://doi.org/10.1016/j.jnucmat.2021.153399
Publication status	Published - Jan 2022
MoE publication type	A1 Journal article-refereed

Funding

The project was funded by EU Horizon 2020 project INCEFA-PLUS from the Euratom research and training programme 2014-2018 under grant agreement N662320. The authors would like to sincerely thank M. Bruchhausen (JRC), M. Vankeerberghen (SCK-CEN), L. de Baglion (Framatome), J.C. le Roux (Electricité de France), L. Doremus (Framatome), A. McLennan (Jacobs), K. Mottershead (Jacobs), T. Lehtikuusi (VTT), J. Lukin (VTT) and all participants in the INCEFA-PLUS Project for their valuable contributions to this work.

Keywords

Environmentally assisted fatigue
Hydrogen
Martensite formation
Stainless steels
Surface finish

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title = "Effect of machining on near surface microstructure and the observation of martensite at the fatigue crack tip in PWR environment of 304L stainless steel",

abstract = "This work highlighted that a ground surface finish and the exposure to a pressurised water reactor (PWR) environment result in a decreased low-cycle fatigue lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 304 L austenitic stainless steel. A ground surface finish promotes fatigue crack initiation and short crack growth especially in a water environment, due to the highly deformed underlying microstructure with high-angle grain boundaries and the grinding marks on surface. Martensite was observed in the vicinity of secondary crack tips in specimens tested in a simulated PWR primary side environment. The aggregated presence of α′- and ε-martensite in the vicinity of the fatigue crack tip can enhance the material's susceptibility to hydrogen-assisted fatigue cracking. Martensite formation was rarely observed in specimens exposed to high temperature air. The phase transformation from γ-austenite to αꞌ-martensite in the PWR primary environment occurred via the intermediate ε-martensite phase.",

keywords = "Environmentally assisted fatigue, Hydrogen, Martensite formation, Stainless steels, Surface finish",

author = "Zaiqing Que and Caitlin Huotilainen and Tiia Sepp{\"a}nen and Jari Lydman and Ulla Ehrnst{\'e}n",

year = "2022",

month = jan,

doi = "10.1016/j.jnucmat.2021.153399",

language = "English",

volume = "558",

journal = "Journal of Nuclear Materials",

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T1 - Effect of machining on near surface microstructure and the observation of martensite at the fatigue crack tip in PWR environment of 304L stainless steel

AU - Que, Zaiqing

AU - Huotilainen, Caitlin

AU - Seppänen, Tiia

AU - Lydman, Jari

AU - Ehrnstén, Ulla

PY - 2022/1

Y1 - 2022/1

N2 - This work highlighted that a ground surface finish and the exposure to a pressurised water reactor (PWR) environment result in a decreased low-cycle fatigue lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 304 L austenitic stainless steel. A ground surface finish promotes fatigue crack initiation and short crack growth especially in a water environment, due to the highly deformed underlying microstructure with high-angle grain boundaries and the grinding marks on surface. Martensite was observed in the vicinity of secondary crack tips in specimens tested in a simulated PWR primary side environment. The aggregated presence of α′- and ε-martensite in the vicinity of the fatigue crack tip can enhance the material's susceptibility to hydrogen-assisted fatigue cracking. Martensite formation was rarely observed in specimens exposed to high temperature air. The phase transformation from γ-austenite to αꞌ-martensite in the PWR primary environment occurred via the intermediate ε-martensite phase.

AB - This work highlighted that a ground surface finish and the exposure to a pressurised water reactor (PWR) environment result in a decreased low-cycle fatigue lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 304 L austenitic stainless steel. A ground surface finish promotes fatigue crack initiation and short crack growth especially in a water environment, due to the highly deformed underlying microstructure with high-angle grain boundaries and the grinding marks on surface. Martensite was observed in the vicinity of secondary crack tips in specimens tested in a simulated PWR primary side environment. The aggregated presence of α′- and ε-martensite in the vicinity of the fatigue crack tip can enhance the material's susceptibility to hydrogen-assisted fatigue cracking. Martensite formation was rarely observed in specimens exposed to high temperature air. The phase transformation from γ-austenite to αꞌ-martensite in the PWR primary environment occurred via the intermediate ε-martensite phase.

KW - Environmentally assisted fatigue

KW - Hydrogen

KW - Martensite formation

KW - Stainless steels

KW - Surface finish

UR - https://www.scopus.com/pages/publications/85119265523

U2 - 10.1016/j.jnucmat.2021.153399

DO - 10.1016/j.jnucmat.2021.153399

M3 - Article

SN - 0022-3115

VL - 558

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

M1 - 153399

ER -

Effect of machining on near surface microstructure and the observation of martensite at the fatigue crack tip in PWR environment of 304L stainless steel

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Keywords

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