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Title: Irradiation-assisted cracking of SA508-304L weldments with 308L groove filler and 309L butter in hot water immersion constant rate extension tests

Journal Article · · Journal of Nuclear Materials
 [1];  [1];  [2]; ORCiD logo [3];  [4]
  1. University of Illinois, Urbana, IL (United States)
  2. Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA (United States)
  3. University of Illinois, Urbana, IL (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
  4. Electric Power Research Institute, Charlotte, NC (United States)

Low alloy SA508 bainitic steel is often welded to 300 series austenitic stainless steel in nuclear power plants. These dissimilar metal weldments use 309L butter applied to the low alloy steel and 308L groove filler material to join the 309L to austenite. High alloy steels (such as the 308L and 309L material used here) have been identified as having greater susceptibility to irradiation-assisted stress corrosion cracking (IASCC). Evidence is presented here of cracking under tensile loads in 309L weldment butter in LWR hydrothermal conditions that correlates irradiation induced changes at δ ferrite–γ austenite phase boundaries and γ–γ grain boundaries; specifically intergranular Cr23C6 precipitates. Cracking is not observed in irradiated 308L groove filler under the same conditions. Both the 309L butter and 308L filler material have a duplex or mixed δ–γ phase microstructure due to solidification during the welding procedure. We have performed constant extension rate autoclave immersion tests in BWR normal water chemistry hot water (288 °C, 10 MPa, 2000 wt. ppb dissolved oxygen, <100 nS/cm conductivity, neutral pH) of proton irradiated (2 MeV, approximately 3 displacements per atom at a depth of 10 μm) tensile specimens. Proton irradiation to the dpa levels used here induced Cr23C6 carbide precipitation at γ–γ grain boundaries and δ–γ phase boundaries in the 309L butter but not the 308L filler. Cracking was observed in the proton-irradiated volume of 309L at these interfaces in the vicinity of the Cr23C6 precipitates. We hypothesis the SA508 is the source of carbon in the 309L butter. Cr depletion at γ–γ grain boundaries was also observed and may also be a root cause of cracking. Furthermore, the 309L butter is under significant tensile residual stress in the weldment that adds to applied tensile loads and this too may be a contributing factor.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE), Nuclear Energy University Program (NEUP); USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
AC05-00OR22725; NE0008699; DE NE0008699
OSTI ID:
2000349
Alternate ID(s):
OSTI ID: 1971158
Journal Information:
Journal of Nuclear Materials, Vol. 581, Issue 1; ISSN 0022-3115
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (27)

Assessment of radiation-induced segregation mechanisms in austenitic and ferritic–martensitic alloys journal April 2011
Irradiation response of delta ferrite in as-cast and thermally aged cast stainless steel journal November 2015
Corrosion of phase and phase boundary in proton-irradiated 308L stainless steel weld metal in simulated PWR primary water journal April 2020
Microstructure, Hardness, and Residual Stress of the Dissimilar Metal Weldments of SA508-309L/308L-304L journal March 2021
Comparison of the microstructure, deformation and crack initiation behavior of austenitic stainless steel irradiated in-reactor or with protons journal January 2015
Theory and experimental background on dimensional changes in irradiated alloys journal October 1994
Dose dependence of the microstructural evolution in neutron-irradiated austenitic stainless steel journal November 1993
A high-resolution characterization of irradiation-assisted stress corrosion cracking of proton-irradiated 316L stainless steel in simulated pressurized water reactor primary water journal May 2022
A historical perspective on understanding IASCC journal April 2019
A review of irradiation effects on LWR core internal materials – IASCC susceptibility and crack growth rates of austenitic stainless steels journal February 2011
Novel features of radiation-induced segregation and radiation-induced precipitation in austenitic stainless steels journal February 2011
Role of irradiated microstructure and microchemistry in irradiation-assisted stress corrosion cracking journal February 2005
Radiation-induced segregation in binary and ternary alloys journal August 1979
Isolating the effect of radiation-induced segregation in irradiation-assisted stress corrosion cracking of austenitic stainless steels journal April 2002
Microstructural development and solidification cracking susceptibility of austenitic stainless steel welds journal January 1991
Theory of transitions in dose dependence of radiation effects in structural alloys journal November 1993
Stress Corrosion Cracking Behavior of Alloys in Aggressive Nuclear Reactor Core Environments journal January 2007
A thermodynamic study of the chromium-carbon system journal October 1987
Modified microstructures in proton irradiated dual phase 308L weldment filler material journal May 2021
On the use of SRIM for computing radiation damage exposure journal September 2013
Quantitative linkage between the stress at dislocation channel – Grain boundary interaction sites and irradiation assisted stress corrosion crack initiation journal May 2019
Impact of localized deformation on IASCC in austenitic stainless steels journal January 2011
Formation and stability of radiation-induced phases in neutron-irradiated austenitic and ferritic steels journal December 1989
Effect of post-irradiation annealing on microstructure and corrosion of proton-irradiated 308L stainless steel weld metal journal October 2020
A theory of radiation-induced segregation in concentrated alloys journal August 1979
An examination of the precipitation behavior of proton irradiated dual phase 308L weldment filler materials journal April 2023
Welding Metallurgy book October 2002