Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED): Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels

Ulla Ehrnsten, Wade Karlsen, Janne Pakarinen, Tapio Saukkonen, Hannu Hänninen

Research output: Chapter in Book/Report/Conference proceedingChapter or book articleProfessional

Abstract

Inhomogeneous microstructures, e.g. grain size, dislocation density etc., always occur in welded structures. Varying manufacturing methods leading to complex strain paths result in highly varying cold work and consequent residual strains. The role of strain localisation is probably playing a key role as a precursor for crack initiation but its mechanisms are still not fully known. If strain localisation occurs by a creep mechanism, the incubation time for crack initiation can be very long, as frequently observed in NPPs. EBSD employed to measure strain distributions in a Type 304 austenitic stainless steel weld shows a high variation in residual strain distribution, which was verified by hardness measurements as well as with residual stress measurements. Strain localisation investigations were also performed on specimens from Super Slow Strain Rate Test (SSSRT) using a very slow strain rate of 1 o 10-8 s-1. This is in the creep strain rate range, where diffusion along dislocation cores and grain boundaries occur together with grain boundary sliding. SSSRT's were performed in simulated BWR environment on sensitized Type 304 and non-sensitised Type 316L austenitic stainless steel either with or without cold deformation. Local variation in the amount of surface cold-work affects crack initiation. Local variations of grain size also affect strain localisation. During crack growth, strain localisation occurs at grain boundaries ahead of the crack tips.
Original languageEnglish
Title of host publicationSAFIR2010
Subtitle of host publicationThe Finnish Research Programme on Safety 2007-2010: Final Report
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Chapter27.2
Pages453-463
ISBN (Electronic)978-951-38-7690-6
ISBN (Print)978-951-38-7689-0
Publication statusPublished - 2011
MoE publication typeNot Eligible

Publication series

SeriesVTT Tiedotteita - Research Notes
Number2571
ISSN1235-0605

Fingerprint

Austenitic stainless steel
Strain rate
Microstructure
Crack initiation
Creep
Grain boundaries
Grain boundary sliding
Stress measurement
Dislocations (crystals)
Crack tips
Crack propagation
Residual stresses
Welds
Hardness

Cite this

Ehrnsten, U., Karlsen, W., Pakarinen, J., Saukkonen, T., & Hänninen, H. (2011). Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED): Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels. In SAFIR2010: The Finnish Research Programme on Safety 2007-2010: Final Report (pp. 453-463). Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Research Notes, No. 2571
Ehrnsten, Ulla ; Karlsen, Wade ; Pakarinen, Janne ; Saukkonen, Tapio ; Hänninen, Hannu. / Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED) : Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels. SAFIR2010: The Finnish Research Programme on Safety 2007-2010: Final Report. Espoo : VTT Technical Research Centre of Finland, 2011. pp. 453-463 (VTT Tiedotteita - Research Notes; No. 2571).
@inbook{05d03ec712ac40e1a81a3f19a8248e58,
title = "Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED): Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels",
abstract = "Inhomogeneous microstructures, e.g. grain size, dislocation density etc., always occur in welded structures. Varying manufacturing methods leading to complex strain paths result in highly varying cold work and consequent residual strains. The role of strain localisation is probably playing a key role as a precursor for crack initiation but its mechanisms are still not fully known. If strain localisation occurs by a creep mechanism, the incubation time for crack initiation can be very long, as frequently observed in NPPs. EBSD employed to measure strain distributions in a Type 304 austenitic stainless steel weld shows a high variation in residual strain distribution, which was verified by hardness measurements as well as with residual stress measurements. Strain localisation investigations were also performed on specimens from Super Slow Strain Rate Test (SSSRT) using a very slow strain rate of 1 o 10-8 s-1. This is in the creep strain rate range, where diffusion along dislocation cores and grain boundaries occur together with grain boundary sliding. SSSRT's were performed in simulated BWR environment on sensitized Type 304 and non-sensitised Type 316L austenitic stainless steel either with or without cold deformation. Local variation in the amount of surface cold-work affects crack initiation. Local variations of grain size also affect strain localisation. During crack growth, strain localisation occurs at grain boundaries ahead of the crack tips.",
author = "Ulla Ehrnsten and Wade Karlsen and Janne Pakarinen and Tapio Saukkonen and Hannu H{\"a}nninen",
year = "2011",
language = "English",
isbn = "978-951-38-7689-0",
series = "VTT Tiedotteita - Research Notes",
publisher = "VTT Technical Research Centre of Finland",
number = "2571",
pages = "453--463",
booktitle = "SAFIR2010",
address = "Finland",

}

Ehrnsten, U, Karlsen, W, Pakarinen, J, Saukkonen, T & Hänninen, H 2011, Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED): Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels. in SAFIR2010: The Finnish Research Programme on Safety 2007-2010: Final Report. VTT Technical Research Centre of Finland, Espoo, VTT Tiedotteita - Research Notes, no. 2571, pp. 453-463.

Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED) : Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels. / Ehrnsten, Ulla; Karlsen, Wade; Pakarinen, Janne; Saukkonen, Tapio; Hänninen, Hannu.

SAFIR2010: The Finnish Research Programme on Safety 2007-2010: Final Report. Espoo : VTT Technical Research Centre of Finland, 2011. p. 453-463 (VTT Tiedotteita - Research Notes; No. 2571).

Research output: Chapter in Book/Report/Conference proceedingChapter or book articleProfessional

TY - CHAP

T1 - Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED)

T2 - Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels

AU - Ehrnsten, Ulla

AU - Karlsen, Wade

AU - Pakarinen, Janne

AU - Saukkonen, Tapio

AU - Hänninen, Hannu

PY - 2011

Y1 - 2011

N2 - Inhomogeneous microstructures, e.g. grain size, dislocation density etc., always occur in welded structures. Varying manufacturing methods leading to complex strain paths result in highly varying cold work and consequent residual strains. The role of strain localisation is probably playing a key role as a precursor for crack initiation but its mechanisms are still not fully known. If strain localisation occurs by a creep mechanism, the incubation time for crack initiation can be very long, as frequently observed in NPPs. EBSD employed to measure strain distributions in a Type 304 austenitic stainless steel weld shows a high variation in residual strain distribution, which was verified by hardness measurements as well as with residual stress measurements. Strain localisation investigations were also performed on specimens from Super Slow Strain Rate Test (SSSRT) using a very slow strain rate of 1 o 10-8 s-1. This is in the creep strain rate range, where diffusion along dislocation cores and grain boundaries occur together with grain boundary sliding. SSSRT's were performed in simulated BWR environment on sensitized Type 304 and non-sensitised Type 316L austenitic stainless steel either with or without cold deformation. Local variation in the amount of surface cold-work affects crack initiation. Local variations of grain size also affect strain localisation. During crack growth, strain localisation occurs at grain boundaries ahead of the crack tips.

AB - Inhomogeneous microstructures, e.g. grain size, dislocation density etc., always occur in welded structures. Varying manufacturing methods leading to complex strain paths result in highly varying cold work and consequent residual strains. The role of strain localisation is probably playing a key role as a precursor for crack initiation but its mechanisms are still not fully known. If strain localisation occurs by a creep mechanism, the incubation time for crack initiation can be very long, as frequently observed in NPPs. EBSD employed to measure strain distributions in a Type 304 austenitic stainless steel weld shows a high variation in residual strain distribution, which was verified by hardness measurements as well as with residual stress measurements. Strain localisation investigations were also performed on specimens from Super Slow Strain Rate Test (SSSRT) using a very slow strain rate of 1 o 10-8 s-1. This is in the creep strain rate range, where diffusion along dislocation cores and grain boundaries occur together with grain boundary sliding. SSSRT's were performed in simulated BWR environment on sensitized Type 304 and non-sensitised Type 316L austenitic stainless steel either with or without cold deformation. Local variation in the amount of surface cold-work affects crack initiation. Local variations of grain size also affect strain localisation. During crack growth, strain localisation occurs at grain boundaries ahead of the crack tips.

M3 - Chapter or book article

SN - 978-951-38-7689-0

T3 - VTT Tiedotteita - Research Notes

SP - 453

EP - 463

BT - SAFIR2010

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Ehrnsten U, Karlsen W, Pakarinen J, Saukkonen T, Hänninen H. Influence of Material, Environment and Strain Rate on Environmentally Assisted Cracking of Austenitic Nuclear Materials (DEFSPEED): Deformation localisation and EAC in inhomogeneous microstructures of austenitic stainless steels. In SAFIR2010: The Finnish Research Programme on Safety 2007-2010: Final Report. Espoo: VTT Technical Research Centre of Finland. 2011. p. 453-463. (VTT Tiedotteita - Research Notes; No. 2571).