Environmentally Assisted Cracking: Theory and Practice : Environment Assisted Cracking
Sponsored by: TMS Corrosion and Environmental Effects Committee
Program Organizers: Jenifer Locke, Ohio State University; Wenjun Cai, Virginia Polytechnic Institute and State University; Bai Cui, University of Nebraska Lincoln; Srujan Rokkam, Advanced Cooling Technologies, Inc.; Kaila Bertsch, University of Wisconsin-Madison
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 30
Location: MS&T Virtual
Session Chair: Bai Cui, University of Nebraska-Lincoln; Kaila Bertsch, Lawrence Livermore National Laboratory
8:00 AM
Introductory Comments: Environmentally Assisted Cracking: Theory and Practice: Jenifer Locke1; 1Ohio State University
Introductory Comments
8:05 AM Invited
Cracking Mechanism of Carbon Steel in Presence of H2S/CO2 and H2S Scavenger, a Theory Based on Electrochemistry, Raman, and Tensile Testing: Vinicio Ynciarte1; Leonardo Caseres2; James Dante2; Brendy Rincon Troconis1; 1University of Texas at San Antonio; 2Southwest Research Institute
Injecting H2S scavenger is a common practice to reduce H2S. However, failures in the form of SCC of steel pipes have been reported. However, there is no knowledge about the effects of this chemistry on the corrosion and cracking mechanism of carbon steel. Based on literature related to corrosion in bicarbonate containing environments and the results of this work, it is suggested that SCC is governed by a possible transition from passive to active kinetics. This transition is a complicated function of sour gas concentration and amine adsorption. In this work, in-situ Raman spectroscopy was used to identify the chemical species present in the test solution prior to and following the scavenging process. In-situ surface enhanced Raman spectroscopy and electrochemical techniques were utilized to measure specific adsorption of amine by-products on the steel, as well as, changes in the surface film composition. Finally, ssrt was performed to evaluate SCC susceptibility.
8:45 AM
Analyzing High-angle Grain Boundary Network Connectivity Using Graph Theory: Syeda Noor E Sumaiya1; Matthew Steiner1; 1University of Cincinnati
Special boundaries with low interfacial energies, such as annealing twins in FCC metals, typically possess enhanced corrosion resistance and can inhibit stress corrosion cracking when incorporated into a microstructure in ways that break up the connectivity of more susceptible interfaces. Such grain boundary engineered microstructures are typically analyzed using parameters than can be readily extracted from EBSD data, notably the fraction of coincident site lattice (CSL) boundaries, or the ratio of triple junctions categorized by how many CSL boundaries they are coordinated with. Other techniques such as fractal analysis have been utilized in a limited number of cases, but none of these methods provides the type of local or directional specificity necessary to address gradated or heterogeneous microstructures. We will present preliminary results using graph theory based boundary connectivity measurements that are better suited to handle non-uniform microstructures and can be automated to run on standard EBSD data.
9:05 AM
Elucidating the Loading Rate Dependence of Hydrogen Environment-assisted Cracking Behavior in Ti, Fe, Al, and Ni-based Structural Alloys: Zachary Harris1; Erin Dubas1; James Burns1; 1University of Virginia
While literature indicates that the applied loading rate (dK/dt) can affect hydrogen environment-assisted cracking (HEAC) behavior, the quantification of dK/dt dependencies and mechanistic understanding of why the applied dK/dt influences HEAC remain limited. In this study, a slow-rising stress intensity (K) framework was utilized to measure HEAC kinetics over dK/dt ranging from 0.2 to 20 MPa√m/hr in Beta-C Ti, AA7075-T651, AA5456-H116, Monel K-500, and Custom 465-H900 stainless steel immersed in 0.6 M NaCl at applied potentials known to promote modest HEAC susceptibility. Results demonstrate that the crack growth rate (da/dt) exhibits two characteristics regimes of behavior with increasing dK/dt across multiple alloys. In particular, a ‘plateau’ regime where da/dt is independent of dK/dt was observed for elevated dK/dt, while a ‘linear’ regime where da/dt linearly scales with dK/dt was noted for slow dK/dt. The implications of these findings on recent testing standardization efforts for HEAC are then discussed.
9:25 AM
Pit-to-Crack Transition in Stress Corrosion Cracking of Type 304 Stainless Steels Under Marine Exposure Conditions: Alana Parey1; 1Sandia National Laboratories; The Ohio State University
Stress corrosion cracking (SCC) poses a threat to austenitic stainless steels when exposed to chloride containing environments during the storage of nuclear waste. The temperature of the canisters decreases over time, during which dust and deliquescent salts lead to the formation of a chloride-rich brine surface environment. Previous laboratory studies often focus on either pit initiation and growth or on crack growth kinetics from a fatigue fractured pre-crack, however, these studies often focus on either pit initiation and growth or on crack growth from a precrack. This study aims to identify the mechanism for the pit-to-crack transition in SCC for type 304 stainless steel in atmospheric marine environments. Experiments will focus on seawater brine conditions that produce microcracking in the absence of externally applied stresses, which is due to residual stresses present on the surface resulting from surface finishing. Testing of these conditions will follow intermittent ripple loading techniques.