Environmentally Assisted Cracking: Theory and Practice: Innovative Techniques in Corrosion Research
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
Tuesday 8:00 AM
March 21, 2023
Room: Sapphire 410B
Location: Hilton
Session Chair: Khalid Hattar, University of Tennessee Knoxville; Yongfeng Lu, University Of Nebraska - Lincoln
8:00 AM Invited
In-situ Electron Microscopy Degradation in Extreme Environments: Eric Lang1; Kathryn Small1; Ryan Schoell1; Nathan Madden1; Nan Li2; Benjamin Derby2; Khalid Hattar1; 1Sandia National Laboratories; 2Los Alamos National Lab
The degradation of materials in coupled environments is often complex, non-intuitive, and highly debated. To this day, the mechanisms underlying the failure in processes ranging from the relatively simplistic hydrogen embrittlement through the much more complex irradiation-assisted stress corrosion cracking (IASCC) are hotly debated and are nuanced depending on the material system and details of the environmental exposure. In this presentation, we will detail our recent development of in-situ electron microscopy techniques to gain greater insight into the active mechanisms at the appropriate length scales. At the nanoscale, we will highlight efforts exploring in-situ transmission electron microscopy (TEM) liquid cell corrosion studies, mechanical testing in gas environments, and mechanical testing during ion irradiation. Similarly, at the microscale, we will highlight recent developments permitting in-situ scanning electron microscopy (SEM) experiments coupling irradiation, fatigue, irradiation, and corrosion. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
8:30 AM
Creep Degradation of Austenitic Steels in CO2 Environment: Kyle Rozman1; Richard Oleksak2; Ömer Doğan2; 1Site Support Contractor; 2National Energy Technology Laboratory
Determining the mechanical properties for materials in CO2 environments is critical for structural alloys in supercritical CO2 power cycle applications. Additionally, to realize the efficiency gains provided by supercritical CO2 power cycles, micro-channel heat exchangers are necessary to transfer heat. In other words, both the mechanical degradation of alloys exposed to CO2 and the effect of material thickness need to be investigated. The authors’ previous research shows the creep life of martensitic steels is degraded in gaseous CO2 environments. The authors also showed that thinner sections of 9Cr-steels and 347h displayed losses of tensile ductility after exposure to gaseous CO2, which is critical for heat exchanger applications with thin sections. This research presents the creep lifetime of austenitic stainless steel, 347H tested in a gaseous CO2 environment. Furthermore, the effect of specimen thickness was investigated with specimens ranging from 2mm to 0.5 mm thick.
8:50 AM
Investigation of Mechanical Properties of Corrosion Products in AA7075-T651 Using In Situ Nanoindentation: Ankit Kumar1; Amey Luktuke1; Hamidreza Torbati-Sarraf1; Daniel Sinclair1; Nikhilesh Chawla1; 1Purdue University
Aluminum alloys are widely used for naval applications due to their excellent specific strength; however, this strength is compromised by their susceptibility to corrosion in seawater. The layers of mixed oxides and hydroxides formed in aqueous environment are crucial to the long-term corrosion resistance of aluminum alloys, and correlations between composition and structural integrity will influence future alloy design. In this work, we systematically investigated the corrosion product of the high-strength AA7075-T651 alloy formed in 3.5 wt.% NaCl solution. The thickness, structure, and composition of the product layer were examined at varied immersion times, showing significant heterogeneity on the micro-scale. A novel in situ nanoindentation technique was applied to correlate the product layer’s structure in a hydrated and dehydrated form to the evolution of mechanical properties. The unique insights into the distribution and evolution of corrosion products in the corrosion layer of these alloys was studied and will be discussed.
9:10 AM
Environmentally Assisted Cracking of Nickel-Based Alloys in Molten Salts Containing Tellurium: Mohammad Umar Farooq Khan1; Lesley Frame2; Stephen Raiman3; 1University of MIchigan; 2University of Connecticut; 3University of Michigan
Tellurium, a fission product in thermal spectrum molten salt reactors, is known to cause embrittlement and cracking of some structural alloys. Grain boundary engineering is a potential method for mitigating cracking of salt-facing alloys. For this work, varying coincidence site lattice (CSL) boundaries were generated by applying different degrees of cold working and heat treatment to IN617. The heat treatment temperature and time were devised to maximize the low CSL boundaries for varied cold work percentages. Samples were then exposed to FLiNaK salt containing Te at 800 °C for 100 hours. Samples were characterized by optical and electron microscopy. This talk will discuss the influence of grain boundary characteristics on corrosive attack and fission product infiltration in molten fluoride salts.
9:30 AM Break
9:50 AM Invited
A Portable Solution to Corrosion Remediation of Sea Ships to Desensitize Severely Sensitized Aluminum Alloys Using Lasers: Yongfeng Lu1; Leimin Deng1; Bai Cui1; 1University of Nebraska - Lincoln
The 5xxx series aluminum (Al) alloy has been widely used in marine environments such as ships. However, it has suffered from sensitization and subsequent intergranular/stress corrosion cracking. Corrosion remediation is usually carried out by sending ships to shipyards for regular maintenance. In this study, a portable laser system was developed to achieve laser surface desensitization (LSD) of severely sensitized 5456 Al alloys. The LSD system is portable and can be used onboard ships during operation. The technique could realize rapid desensitization selectively on localized surface regions and within controllable depths. A degree of sensitization (DoS) of 1.7 mg/cm2, which was even lower than the original material, was achieved from severely sensitized 5456 Al alloys (a DoS of over 46.8 mg/cm2). Moreover, LSD not only reversed the sensitization with no loss of mechanical properties, but it also significantly enhanced the future sensitization resistance of Al alloys at the same time.
10:20 AM
Site Specific Multimodal In-situ Study of Early-Stage Corrosion of Model Fe-Cr-Ni Alloys Using Electrochemical Atomic Force Microscopy: Tingkun Liu1; Cheng-Han Li1; Matthew Olszta1; Jinhui Tao1; Arun Devaraj1; 1Pacific Northwest National Laboratory
Stainless steels are used in a myriad of engineering applications including in construction, automotive and nuclear reactors. Developing accurate predictive mechanistic models for corrosion kinetics of stainless steel specifically in chloride environments has been a topic of research studies over many decades. Quantitative, spatially-resolved in-situ studies of stainless steel corrosion kinetics can be very valuable for such predictive corrosion kinetics model development. Towards this goal, we demonstrate the ability to quantitatively analyze the corrosion kinetics of a model austenitic Fe-18Cr-14Ni alloy using systematic in situ liquid cell electrochemical AFM studies. The kinetics of corrosion at austenite grain boundaries are imaged in high resolution in deuterium chloride solution both in the presence and absence of electrochemical bias. The insights gained in this work and the in-situ liquid cell AFM methodology are relevant to the broader areas for understanding corrosion, electrochemical corrosion, stress corrosion cracking, and hydrogen embrittlement in stainless steel.
10:40 AM
Exploring Environmentally-Assisted Cracking in Liquid Metal and Molten Salt Advanced Reactor Coolant Environments: Samuel Briggs1; Dustin Mangus1; Jake Quincey; Xavier Quintana1; Guillaume Mignot1; Julie Tucker1; 1Oregon State University
While complex materials degradation modes, including stress corrosion cracking, corrosion fatigue, and irradiation-assisted stress corrosion cracking, have been studied extensively for light water reactor environments, these phenomena are not well-understood in proposed advanced reactor systems. Due to higher temperatures and distinct corrosion mechanisms, these effects are expected to manifest in significantly different ways in these non-aqueous coolant environments. Oregon State University has recently developed unique facilities enabling testing of fracture mechanics-based environmentally-assisted cracking in liquid sodium and molten salt environments. These facilities combine some mechanical loading mechanism (e.g., a traditional electronic actuator) with a controlled coolant environment of interest, enabling various types of standardized tests exploring environmentally-assisted cracking within a wide range of operating conditions relevant to several preeminent advanced reactor designs. Initial testing has focused on 316L stainless steel. Slow strain rate tests in molten LiF-NaF-KF (FLiNaK) eutectic salts and U-bend tests in liquid sodium environments will be discussed.
11:00 AM
Liquid Metal Embrittlement Behavior of Dual-Phase Steels: The Influence of Microstructure and Strain Rate.: Pallavi Pant1; Benjamin Hilpert2; Holger Shubert2; Luke Brewer1; 1The University of Alabama; 2Mercedes Benz AG
This presentation will describe the liquid metal embrittlement (LME) of dual-phase steels and its relationship with the steel microstructure. These steels are zinc coated for corrosion protection, but during welding, they can experience LME. The LME response was studied by hot ductility testing using a Gleeble thermo-mechanical simulator. The DP1000HD steel exhibited severe LME susceptibility; in contrast, DP800 and DP1200LY steels were immune to LME. The LME severity was temperature-dependent and was limited to a range of temperatures, 750-900˚C. SEM-based fractography showed that when LME occurred, it advanced in an intergranular fashion. Environmental fracture, such as LME, is generally strain rate sensitive, and we will discuss the impact of strain rate on the LME fracture over a range of 10-3 - 10 strain/second. Detailed microscopic investigation of the parent and retained austenite using EBSD and TEM is being used to link the steel microstructure to its LME response.