Resisting Degradation from the Environment: A Symposium Honoring Carolyn M. Hansson’s Research and Pioneering Experiences as a Woman in STEM: Talks to Introduce Posters I
Sponsored by: TMS: Corrosion and Environmental Effects Committee, TMS: Steels Committee
Program Organizers: Jenifer Locke, Ohio State University; Brendy Rincon Troconis, University of Texas at San Antonio; Ashley Paz y Puente, University of Cincinnati; George Gray, Los Alamos National Laboratory; Suveen Mathaudhu, Colorado School of Mines; David Shifler, Office of Naval Research
Monday 8:00 AM
October 10, 2022
Room: 404
Location: David L. Lawrence Convention Center
Funding support provided by: Office of Naval Research
Session Chair: Jenifer Locke, Ohio State University
8:00 AM
The Effect of Microstructural Surface States on the Corrosion of Additively Manufactured 316 Stainless Steel: Nicole Tailleart1; G. Cheek2; Carlos Hangarter1; Andrew Geltmacher1; S. Feng1; S. Olig1; 1US Naval Research Laboratory; 2US Naval Academy
Using AM (Powder Bed Fusion) 316 stainless steel, this work seeks to sort out the nuanced differences in surface chemistry, microstructure and/or corrosion electrochemistry changes resulting from refined electropolishing operations by combining minimal material removal with selective localized electrochemistry and chemical surface analyses of the printed microstructures. SEM, EDS, and confocal scanning laser (CSLM)/digital microscope, and cyclic polarization were utilized as the primary characterization methods. SEM investigations indicated that the sample material was unexpectedly contaminated with residual Inconel 718 during the printing process. With increasing depth from the as-printed surface, observed metastable pitting, surface roughness, and passive current all decreased. This process was repeated for uncontaminated AM 316 stainless steel. Other on-going AM corrosion efforts are also introduced, including in-situ XCMT corrosion experiments of AM 316 stainless and full immersion studies of AM samples in a marine environment.
8:20 AM
Galvanic Corrosion of Active and Passive Steel Bars with Different Area Ratios: Amir Poursaee1; Zheng Dong2; 1Clemson University; 2Zhejiang University of Technology
The present study investigated the corrosion behavior of coupled active and passive steel bars in a concrete simulated environment. Three different active-to-passive areas (A/P) ratios, i.e., A/P=1/1, 1/3, 1/20, were studied. Three cells were prepared for each group of A/P ratio: an individual cell with active steel specimens, individual cell with passive steel specimens, and a coupled cell that connected active and passive steel bars. All specimens were immersed in a concrete pore solution for 14 days; then, 3 wt.% NaCl was added to the cells. Results of the electrochemical tests indicated that coupling changed the corrosion behavior of the active steel. In the case of A/P=1/1, the corrosion was mainly in the form of localized corrosion, whereas in the case of A/P=1/20, more general and severe corrosion was observed. In addition, the coupling increased the anodic and cathodic Tafel slopes, which are closely related to the iron oxidation rate.
8:40 AM
Corrosion and Environmentally Assisted Cracking (EAC) Evaluation of Additively Manufactured (AM) High Strength Precipitation Hardened Steel (UNS S17400): Michelle Koul1; Conner Panick2; 1United States Naval Academy; 2U.S. Navy
AM 17-4PH steel heat treated to the H1100 condition was characterized using the constant extension rate testing method in 3.5 wt.% NaCl solution. Results were examined as a function of specimen orientation with respect to the build direction and compared to the H1100 wrought condition. Select AM specimens showed susceptibility to corrosion which correlated with a significantly decreased ductility and strength. Scanning electron microscopy of these specimens indicated the presence of unfused powder particles and voids in the bulk AM material that appear to be susceptible to corrosion. As-melted surfaces within these voids contained Si oxides, large Nb particles, Cu precipitates and Cr depletion from the subsurface. AM materials contained a grain boundary phase that correlated with microscopically ductile intergranular fracture. Elemental grain boundary segregation/depletion was not observed but (reverted) austenite was identified in electron backscatter diffraction images.
9:00 AM
Evaluating the Sensitivities of SCC Susceptibility in Stainless-steel Nuclear Waste Storage Containers: Sarah Blust1; James Burns1; 1University of Virginia
Used nuclear fuel (UNF) is currently stored across the US in passively cooled stainless steel dry storage canisters (DSC). Due to the design of the DSC, aerosols from the outside environment are able to deposit on the stainless-steel canisters. Over time the deposited aerosols will deliquesce on the canisters to form concentrated salt brines resulting in localized corrosion, which when coupled with the high residual stress around the welds can lead to stress corrosion cracking (SCC). The scope of the work presented is to investigate the boundaries of SCC to varying sensitivities such as environmental factors, microstructure variability, and material composition. These sensitivities will allow for recommendations to be made for canister environmental monitoring and which variables are of the greatest concern for SCC of the UNF canisters.
9:20 AM
Corrosion of Fe-Cr-Mn Stainless Steel in Supercritical Water: Joey Kish1; Shooka Mahboubi1; Yinan Jiao1; 1Mcmaster University
Corrosion of an austenitic Fe-Cr-Mn stainless steel (Nitronic® 32, N32) in supercritical water (25 MPa), relative to Fe-Cr-Ni stainless steel (Types 310 and 316L) was determined. Mass change measurements revealed N32 is less susceptible to corrosion than Type 316L, but more susceptible than Type 310 stainless steel after 500 h immersion at 550 °C. The relative difference in corrosion cab be explained by the protective ability of the oxide scales formed, which, for N32, consists of an outer Mn-rich (Mn,Cr)2O3 layer residing on a Cr-rich (Cr,Mn)3O4 inner layer, as revealed by X-ray diffraction and electron microscopy techniques. A rather significant Mn depletion zone accompanies corrosion, which transforms the near-surface region from austenite to ferrite. The suitability of Fe-Cr-Mn alloy fuel claddings for the supercritical water-cooled reactor concept is discussed within the context of the findings.
9:40 AM
Oxidation Behavior of Model FeCrAl Steel and APMT Alloy After Exposure in Steam: Kinga Unocic1; Kenneth Kane1; Yukinori Yamamoto1; Bruce Pint1; 1Oak Ridge National Laboratory
Over past few years, number of research has been conducted to address accident tolerant fuel cladding for light water nuclear reactors. Alloys with lower Cr contents are desired for radiation damage resistance during the operation.Thus, a model wrought ferritic Fe-12Cr-6Al-2Mo-0.2Si-0.03Y (wt%) steel (C26M) alloy was studied. For comparison, a commercial Kanthal® APMT alloy (Fe-22Cr-5Al-3Mo-0.6Si-0.18Y) was also evaluated. Both alloys were exposed for a short-time (4 hours) in a) steam and b) air between 1200-1475°C temperature range. Characterization of the alumina scales using scanning transmission electron microscopy (STEM) found that the scale morphology formed in steam was affected by the alloy Y content, which segregated along scale grain boundaries at 1200°C. However, after 4 hours at 1475°C, the scale morphology was drastically different and reactive elements along grain boundaries were diminished. Further, differences in scale morphology in both alloys between air and steam will be discussed.
10:00 AM Break
10:20 AM
Corrosion and Biocompatibility of 316L Stainless Steels Fabricated by Selective Laser Melting: Erica Murray1; 1Louisiana Tech University
Surgical grade stainless steel, 316L was fabricated by selective laser melting at a laser power of 100 W where the laser scan speed was varied from 800 – 1200 mm/s resulting in samples with different microstructural features. Electrochemical impedance spectroscopy was used to characterize the corrosion behavior 316L samples during exposure to simulated body fluid (Locke’s solution) at approximately 37 °C over 15 days. The role of microstructure on corrosion of the 316L stainless steel samples in simulated body fluid was evaluated with respect to: pitting initiation and cessation, localized and intergranular corrosion, and passivation and repassivation kinetics. Also, biocompatibility was investigated on samples placed in 2D cultures of bone marrow related stem/stromal cells (MC3T3) to evaluate the toxic response of the 316L SLM samples. Coverage of MC3T3 on 316L surfaces was correlated with electrochemical corrosion data.
10:40 AM
Investigation of Crack Initiation in Hydrogen Embrittled Ni-base Alloy 725: Mengying Liu1; Lai Jiang2; Michael Demkowicz3; 1Washington and Lee University; 2Texas A&M University ; 3Texas A&M University
The factors responsible for hydrogen embrittlement (HE) of metals remain imperfectly understood, with prevailing theories emphasizing H-induced decohesion or H-enhanced localized plasticity (HELP). We use in situ tensile testing to clarify the role of slip in the initiation of intergranular cracks in alloy 725. We quantitatively assess the HELP hypothesis using melt extraction to measure H content and digital image correlation (DIC) to analyze localized plastic strains during in situ tensile tests in a scanning electron microscope (SEM). We find localized slip is neither necessary nor sufficient for crack initiation. The role of slip is likely to reduce local cohesive strength and create local stress concentrations that promote decohesion. Understanding the mechanism can help with improving future alloy design and lifetime prediction.
11:00 AM
Characterization of Internal Oxidation in Alloy 690 and Model Ni Alloys: Masoud Zakeri1; Ibrahim Ogunsanya1; Ali Ashrafriahi1; Roger Newman1; 1University of Toronto
Oxidation behavior of Alloy 690 and model Ni alloys (Ni-30Cr-10Fe and Ni-35Cr-10Fe) was investigated after exposure to hydrogenated steam at 480 °C and 1 atm, considered to simulate primary water in pressurized water reactor. The alloys underwent internal oxidation intragranularly, resulting in the expulsion of Ni to the surface. In Alloy 690, protective external Cr-rich oxides formed around grain boundaries and hindered oxygen penetration and intergranular oxidation. Over time, a compact Cr-rich healing layer developed at internal oxidation front initiating at the grain boundary surface oxide, effectively stopping further internal oxidation penetration into the bulk alloy. In Ni-30Cr-10Fe and Ni-35Cr-10Fe, their increased Cr concentration resulted in increased intergranular carbides. These carbides served as Cr-reservoir and caused higher outward Cr flux and significant reduction of internal oxidation depth. Short circuit diffusion along grain boundaries and diffusion-induced grain boundary migration dramatically increased diffusion of reactive components and promoted protective oxide layer formation.
11:20 AM Fireside Chat with Prof Carolyn Hansson