Environmentally Assisted Cracking: Theory and Practice: Stress Corrosion Cracking II
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
Wednesday 2:00 PM
February 26, 2020
Room: Theater A-10
Location: San Diego Convention Ctr
Session Chair: Yiren Chen, Argonne National Laboratory; Srujan Rokkam, Advanced Cooling Technologies, Inc.
2:00 PM
On the Stress Corrosion Cracking Behavior of a Precipitation-hardened Martensitic Stainless Steel under Atmospheric Exposure Conditions: Zachary Harris1; Keiko Amino1; Patrick Steiner1; James Burns1; 1University of Virginia
The stress corrosion cracking (SCC) behavior of the precipitation-hardened martensitic stainless steel, Custom 465-H900, under atmospheric exposure conditions was assessed via a slow-rising stress intensity (K) testing framework coupled with electrochemical potential measurements. Three experimental configurations were evaluated in this study using 0.6 M NaCl solution as the bulk electrolyte: (1) continuous misting, (2) direct wicking of solution into the specimen starter notch, and (3) full immersion. Experiments revealed that the threshold stress intensity was reduced in atmospheric environments relative to full immersion testing, with the following order from least to most susceptible: full immersion > misting > wicking. Conversely, the Stage II crack growth rate was found to be nominally identical across all tested environments. These results are assessed in the context of proposed hydrogen embrittlement mechanisms, with particular focus on the contributions of the electrolyte geometry and open circuit potential evolution during testing to the local crack-tip conditions.
2:20 PM
Understanding the Effect of Anodic Polarization on SCC Resistance of AA6111-T8 used for Automotive Applications: Katrina Catledge1; Mark Nichols2; Gerald Frankel1; Jenifer (Warner) Locke1; 1The Ohio State University; 2Ford Research and Advanced Engineering
6xxx Al-Mg-Si alloys are age-hardenable and considered resistant to stress corrosion cracking (SCC) in comparison to other age-hardened aluminum alloys. For greatest weight savings, joining of 6xxx alloys with carbon fiber reinforced polymer (CFRP) is being considered. However, galvanic coupling may reduce the SCC resistance of 6xxx alloys. This research addresses the effect of anodic polarization on the SCC resistance of AA6111-T8 to simulate galvanic coupling with CFRP. Slow rising displacement testing in 3.5 wt.% sodium chloride shows that the SCC threshold stress intensity (KTH) decreases from 16-18 MPa√m when held at the freely corroding potential (OCP), to less than 6 MPa√m at 100mVSCE above OCP. Constant stress intensity testing at OCP conditions and at applied anodic polarization levels is used to verify expected cracking behavior based on determined KTH. This work is supported by the Department of Energy under award number DE-EE0007760 through a sub-award under PPG Industries, Inc.
2:40 PM
Modeling of Corrosion Damage, Crack Dynamics and Fracture using a Physics-based Meshless Peridynamics Approach: Srujan Rokkam1; Masoud Behzadinasab1; Max Gunzburger2; Nam Phan3; Sachin Shanbhag2; Kishan Goel3; 1Def-Aero, Advanced Cooling Technologies Inc; 2Florida State University; 3Naval Air Systems Command
Environmental assisted corrosion cracking is a major cause for structural damage in many engineering applications. In this work, we discuss a Peridynamic (PD) approach for physics-based modeling of corrosion damage phenomena which can be applied to model crack growth and failure due to either stress corrosion cracking (SCC) or corrosion fatigue (CF). PD approach is a reformulation of classical computational mechanics that enables modeling of crack growth problem without the need to re-mesh the domain. The presentation will focus on two aspects: (i) how multiphysics aspects of corrosion damage can be modeled using nonlocal PD approach, (ii) demonstration of corrosion crack dynamics in surrogate aluminum alloys. The developed framework captures ductile damage behavior as well crack path dynamics without the drawbacks of conventional theories. This work was funded by U.S. Navy/NAVAIR through STTR program, Contract N68335-15C-0032, awarded to Advanced Cooling Technologies, Inc. The simulations used NSF-XSEDE allocation grants TG-SBR150001.
3:00 PM
Stress Corrosion Cracking Behavior of Austenitic Stainless Steel SS304 for Dry Storage Canisters in Simulated Sea-water: Nilesh Kumar1; Leonardi Tjayadi2; Korukonda Murty2; 1University of Alabama, Tuscaloosa; 2North Carolina State University
A number of recent studies have suggested that dry storage canisters (DSCs) made of austenitic stainless steel SS304 to store spent nuclear fuel located along coastal region may undergo stress corrosion cracking (SCC) if their useful life is extended due to lack of a permanent underground burial repository. It, therefore, becomes necessary to understand SCC behavior of SS304 in marine environment. We report here our results on SCC of SS304H in a simulated sea-water using fracture mechanics approach as a function of temperature. The average crack growth rates were noted to be 0.975 x 10^-10 ± 9.528 x 10^-12, 3.258 x 10^-10 ± 9.551 x 10^-11 and 1.580 x 10^-9 ± 2.593 x 10^-10 m/s at 22, 37, and 60 °C, respectively. The activation energy of the crack-growth process was estimated to be 60.9 kJ/mol corresponding to diffusion of hydrogen in steel. Optical microscopy revealed intergranular nature of the crack-growth.
3:20 PM Break
3:40 PM Invited
Cracking of Reactor Core Internal Materials in LWR Environments: Yiren Chen1; 1Argonne National Laboratory
The service performance of reactor core internal components is critical for the long-term availability and stability of light water reactors (LWRs). Subject to intensive neutron irradiation and corrosive high-temperature coolant, core internal materials are vulnerable to irradiation- and environment-induced degradations during power operation. To evaluate the long-term effects of neutron irradiation on the cracking behavior of reactor core materials, crack growth rate and fracture toughness J-resistance curve tests are performed on a Type 304 stainless steel harvested from a decommissioned pressurized water reactor. These decommissioned materials provide an excellent opportunity to assess the extent of material degradation under prototypical LWR irradiation and service conditions, eliminating any uncertainties associated with laboratory irradiation experiments. The tests are performed at ~315°C in low-corrosion-potential environments. The results are compared with the current crack growth models for irradiated stainless steels and are discussed in the context of cracking mechanisms under LWR relevant conditions.
4:20 PM
Pitting Corrosion Analysis on Austenitic Stainless Steel Welds in Brine for Understanding of Chloride-induced Stress Corrosion Cracking of Spent Nuclear Fuel Dry Storage Canisters: Seunghyun Kim1; Gidong Kim1; Chang-Young Oh1; Ji Hyun Kim2; Sang-Woo Song1; 1Korea Institute of Materials Science; 2Ulsan National Institute of Science and Technology
This study aims to investigate pitting corrosion behavior of gas-tungsten arc welded (GTAW) austenite stainless steels in brine. The austenitic stainless steels (e.g., 304L, 316L) have been considered as a promising candidate material for spent nuclear fuel dry storage canisters. By the combination of decay heat from stored fuels, deliquescence of salts by humidity from flying seawater, and residual stress from welds, chloride-induced stress corrosion cracking (CISCC) has been considered as potential threat in long-term service of the system. As pitting corrosion is known as to initiate CISCC, we investigated the pitting corrosion behavior of the stainless steels in brine condition. Specimens were manufactured by GTAW and the pitting corrosion was analyzed by multiple electrochemical techniques. The effects of microstructure, residual stress on pitting corrosion will be further investigated.
4:40 PM
Mechanistic Studies of Intergranular Stress Corrosion Cracking in Al-Mg Alloys under Atmospheric Exposure Conditions: Patrick Steiner1; James Burns1; 1University of Virginia
To date the majority of IG-SCC studies have been performed in electrochemically controlled immersion environments. These can differ drastically from atmospheric environments, that are more typical of real-life service conditions, and have been seen to highly affect the underlying IG-SCC mechanism and crack growth rates as compared to analogous immersion studies. Atmospheric environments are generally characterized by three key parameters: 1) a decrease in solution volume and water layer thickness 2) an increase in solution ion concentrations, especially chloride, and 3) the removal of any external governing potentiostat or cathodic source. The resulting effects of these key characteristics are complex and often contradictory, thus in order to gain a clear picture of the governing factor(s) controlling atmospheric environment IG-SCC growth an effort has been made to individually isolate the effects of each of the key parameters to better inform pertinent modelling and mitigation strategies originally derived from full immersion environments.