Environmentally Assisted Cracking: Theory and Practice: Stress Corrosion Cracking I
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Bai Cui, University of Nebraska Lincoln; Raul Rebak, GE Global Research; Srujan Rokkam, Advanced Cooling Technologies, Inc.; Jenifer Locke, Ohio State University

Monday 2:00 PM
February 28, 2022
Room: 201D
Location: Anaheim Convention Center

Session Chair: Peter Andresen, Andresen Consulting; Yong Yang, University of Florida; Fei Wang, University of Nebraska Lincoln


2:00 PM  Invited
Stress Corrosion Cracking Guidelines Challenges: Peter Andresen1; 1Andresen Consulting
     As fatigue and overload have been quantified in design codes, environmental cracking (stress corrosion cracking (SCC) and corrosion fatigue) has become more common, and is less well understood than other corrosion phenomena. When environmental cracking develops rapidly, the challenges in quantification and modeling are not nearly as immense as when long life (such as 20 – 80 years) is a requirement. Short term tests that represent a time-acceleration of 100 – 2000X cannot be expected to be (nor are they) adequately sensitive, and tests that focus on initiation cannot account for the evolution of the surface over long-time environmental exposure – indeed, often the nature and consistency of engineering surfaces are poorly known. Functionality (on stress, concentration/pH, temperature, microstructure, etc.) cannot be extrapolated by 100 – 2000X in time with any confidence. Such tests have value, but their shortcomings must be understood. SCC growth rate tests with high resolution crack following hold the greatest promise for quantifying SCC susceptibility and identifying dependencies, and they characterize the response of the overall structure, not just the surface. Such tests involve experimental sophisticated and testing expertise, and a recently published SCC Guidelines (www.epri.com) provides detailed examples of historical errors and recommended practices.

2:35 PM  
Peening Technologies to Mitigate Initiation and Resurgence of Stress Corrosion Cracking in Dry Cask Storage Stainless Steel Canisters: John Lacy1; Hwasung Yeom1; Stan Bovid2; Micheal Kattoura2; Andrew Tieu3; Willie Bloom3; Jonathan Tatman4; Kenneth Ross5; Kumar Sridharan1; 1University of Wisconsin-Madison; 2LSP Technologies; 3VLN Advanced Technologies; 4Electric Power Research Institute ; 5Pacific Northwest National Laboratory
    Long-term storage of used nuclear fuel (UNF) is one of the key issues for sustainability of the current Light Water Reactor (LWR) fleet. The stainless-steel canisters used for storage in dry cask storage systems (DCSS) have a propensity for chloride-induced stress corrosion cracking (CISCC) due to combination of tensile stress at welds, susceptible microstructure, and corrosive chloride salt environment. This research is aimed at evaluating a variety of peening technologies, including, shot peening, laser shock peening, and pulsed water jet peening to mitigate initiation and growth of CISCC in DCSS canisters. Microstructural developments in the peened region including grain refinement and reorientation, deformation-induced martensite formation, and dislocation entanglements were examined. Compressive residual stress measurements and corrosion testing have been conducted to evaluate the effect peening has on pitting corrosion behavior and stress corrosion cracking.

2:55 PM  
NOW ON-DEMAND ONLY - An Investigation of Stress Corrosion Cracking Performance for Naturally Aged 5xxx Alloys: William Golumbfskie1; Matthew McMahon1; Emily Holcombe1; Mitra Taheri2; 1Naval Surface Warfare Center-Carderock Division; 2Johns Hopkins University
     Marine Grade (5xxx) aluminum alloys are considered sensitized when magnesium precipitates out of solution forming a deleterious β-phase (Mg2Al3) along the grain boundaries, rendering them susceptible to stress corrosion cracking (SCC). The extent and rate of sensitization is dictated by exposure to elevated temperatures. Current research uses accelerated heat treatments in laboratory settings to simulate sensitization occurring naturally at lower temperatures and longer times.This study will evaluate material performance of thin plate naturally aged 5xxx aluminum compared against laboratory aged specimens. Slow rising stress intensity testing is used to quantify the effect of sensitization on IG-SCC susceptibility, identifying differences in threshold stress intensity in potentiostatic conditions and full seawater immersion. The microstructure and extent of sensitization will be characterized using microscopy coupled with electron backscatter diffraction (EBSD) and sensitization testing. This study will evaluate naturally aged and lab aged specimens, providing insight for microstructures with increased resistance to SCC.

3:15 PM  
Effect of Water on Localized Corrosion and Stress Corrosion Cracking of Stainless Steels in Chloride Environments: Narasi Sridhar1; Liu Cao2; Angeire Huggins Gonzalez2; Ramgopal Thodla2; 1MC Consult LLC; 2DNV
    The activity of water is an important, but often underappreciated, aspect of localized corrosion and Environmentally Assisted Cracking (EAC). The effect of water activity in aqueous systems is difficult to study because of the ubiquity of water. The localized corrosion and stress corrosion cracking (SCC) resistance of stainless steels in methanolic environments are examined in this paper from the perspective of the role of water activity. The SCC of stainless steels in methanolic environments occur in conjunction with localized corrosion. The effect of environmental chemistry in terms of water and chloride concentration on the SCC of stainless steels is presented. The localized corrosion and SCC became less severe in methanolic solutions with the addition of water and more severe with the increase in chloride concentration.