Environmentally Assisted Cracking: Theory and Practice: Hydrogen Embrittlement 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
Thursday 8:30 AM
February 27, 2020
Room: Theater A-10
Location: San Diego Convention Ctr
Session Chair: Joshua Kacher, Georgia Institute of Technology; Kaila Bertsch, Lawrence Livermore National Laboratory
8:30 AM Invited
Mechanistic Model for Fatigue Crack Growth in the Presence of Hydrogen: Seyedehzahra Hosseinisarani1; Mohsen Dadfarnia2; Masanobu Kubota3; Akihide Nagao3; Brian Somerday3; Petros Sofronis1; Robert Ritchie4; 1Kyushu University; University of Illinois at Urbana-Champaign; 2Kyushu University; Seattle University; 3Kyushu University; 4Kyushu University; University of California, Berkeley
Hydrogen accelerated fatigue crack growth is a severe mode of environmental failure for which a mechanistic model is still lacking. In this study, we attempt to theoretically model fatigue crack propagation induced by alternating crack tip plastic blunting and re-sharpening. The model which is so designed that it relies on inputs from experiments that measure macroscopic material behavior such as the uniaxial cyclic straining can successfully reproduce the response in the Paris regime. The model is used to investigate the dependence of fatigue crack growth on the hydrostatic constraint. Lastly, we explore the hydrogen effect on crack propagation under equilibrium conditions of hydrogen with material straining. The hydrogen effect is accounted for through the modification of the hardening response of the material according to the experimentally observed acceleration of the motion and generation of dislocations.
9:10 AM
First-principles Investigation of Hydrogen Trapping in Chemistry Dependent Vacancies of Fe Cr Ni Alloys: Patrick Thomas1; Benjamin Sikora1; 1Honeywell
Hydrogen-induced embrittlement (HE) poses a key unresolved manufacturing issue for alloys operating in H-rich environments. The trapping of hydrogen by vacancies and dislocations has been shown to increase susceptibility to HE. A first-principles study on the chemistry-dependent trapping capabilities of vacancies in fcc, bcc, and fcc-bcc ternary alloys was completed to understand the effects of defect atom migration on the trapping of hydrogen. A large library of 32 atom Fe Cr Ni alloys was created by Monte Carlo and cluster expansion method. Hydrogen was introduced in randomly placed vacancies in the structures and trapping energies calculated using density functional theory for varying concentrations of Fe Cr Ni and common defect elements adjacent to the vacancy.The Department of Energy’s Kansas City National Security Campus is operated and managed by Honeywell Federal Manufacturing & Technologies, LLC under contract number DE-NA0002839.
9:30 AM
Crystal Plasticity Modeling of Hydrogen Concentration Ahead of a Crack Tip in FCC Steel: Theodore Zirkle1; Tang Gu1; Ben Anglin2; Clint Geller3; David McDowell1; 1Georgia Tech; 2Naval Nuclear Laboratory ; 3Naval Nuclear Laboratory
The effect of hydrogen on deformation, fracture, and fatigue of metals has been a long standing issue with numerous historical mechanisms proposed. General agreement on the mechanism for hydrogen embrittlement, however, remains elusive. Of specific interest in the fatigue of materials is the experimentally observed tendency of hydrogen to cluster around a crack tip. To study this phenomenon, we employ a coupled diffusion-crystal plasticity model to extend the Sofronis-McMeeking hydrogen transport model to the continuum level in order to simulate the heterogeneous distribution of hydrogen ahead of a crack tip. FCC steel material behavior and hydrogen diffusion are modeled using a User Material Subroutine and User Material Heat Equation Subroutine in the finite element package ABAQUS. We discuss the implications of the model results and propose paths forward to leverage the continuum level understanding of heterogeneous hydrogen concentrations to inform new constitutive equations in the study of hydrogen embrittlement.
9:50 AM
Elucidating the Loading Rate Dependence of Hydrogen Environment-assisted Cracking Behavior in a Ni-Cu Superalloy: Zachary Harris1; Erin Dubas1; Allison Popernack1; Brian Somerday2; James Burns1; 1University of Virginia; 2Independent Consultant
Though literature indicates that the applied loading rate (dK/dt) can affect hydrogen environment-assisted cracking (HEAC) behavior, quantification of dK/dt dependencies, as well as mechanistic understanding of how dK/dt influences HEAC, remains limited. In this study, a slow-rising stress intensity (K) testing framework was utilized to measure HEAC kinetics in Monel K-500 immersed in 0.6 M NaCl and polarized to -950 mVSCE at dK/dt ranging from 0.2 to 20 MPa√m/hr. Results confirm a strong influence of dK/dt on HEAC, with crack growth rates (da/dt) exhibiting two characteristic regimes of behavior depending on applied dK/dt. In particular, a ‘plateau’ regime where da/dt is independent of dK/dt was observed for dK/dt > 2 MPa√m/hr, while a ‘linear’ regime where da/dt linearly scales with dK/dt was observed for dK/dt < 2 MPa√m/hr. The implications of these results on recent testing standardization efforts for environment-assisted cracking are then discussed.
10:10 AM Break
10:30 AM
Comparison of Fracture Morphologies and Hydrogen States Present in Vicinity of Fracture Surface Obtained by Different Methods of Evaluating Hydrogen Embrittlement of DP and TRIP Steels: Daichi Asari1; Kenichi Takai1; Satoshi Mizokami2; Mitsugi Fukahori2; 1Sophia University; 2Mazda Motor Corporation
Fracture morphologies and hydrogen states present in vicinity of fracture surface for DP and TRIP steels have been investigated. The fracture surfaces were obtained by SSRT at strain rates of 8.33×10-6 s-1, 1.66×10-6 s-1 and CLT under the same hydrogen charging condition. Fracture surfaces were observed using SEM. Hydrogen states present in the vicinity of fracture surface were analyzed using a thermal desorption analysis immediately after the specimens were fractured. Results showed that the critical fracture strengths were in the order of [SSRT(8.33×10-6 s-1)">" CLT">" SSRT(1.66×10-6 s-1)] for both specimens. DP specimen fractured by SSRT at higher strain rate had only lower-temperature peak from hydrogen desorption profile, however, the ones fractured by SSRT at lower strain rate and by CLT had both lower-temperature peak and higher-temperature peak. Furthermore, the fracture surfaces changed from intergranular to quasi-cleavage fracture corresponding to the decrease in fracture strength from both specimens.
10:50 AM
Comparison Study on the Hydrogen Embrittlement Susceptibility of High Hardness Steels: William Williams1; David Salley1; Haley Doude1; Wilburn Whittington1; David Wipf2; Krista Limmer3; Daniel Field3; Kevin Doherty3; Hongjoo Rhee1; 1Center for Advanced Vehicular Systems; 2Mississippi State University; 3US Army Research Laboratory
Hydrogen embrittlement poses a risk for high hardness steel (HHS) and can cause premature failure of the material. An investigation into the susceptibility of HHS to hydrogen embrittlement was performed for selected alloys. Alloys were mechanically evaluated for hydrogen susceptibility by hydrogen charging, zinc electroplating, and slow-strain rate testing of tensile specimens. The results were compared to the performance of the as-received materials. After evaluating the degradation of mechanical properties due to hydrogen embrittlement, the efficacy of hydrogen traps was investigated by conducting hydrogen permeability tests on each material. A comparison was made between the onset of hydrogen embrittlement within the alloy and the diffusivity of hydrogen within the material.
11:10 AM
Crack Initiation and Propagation Analyses of Hydrogen-related Fracture Surfaces of Tempered Martensitic Steel: Takahiro Chiba1; Takashi Yasukawa1; Kenichi Takai1; 1Sophia University
The hydrogen-related crack initiation and propagation in tempered martensitic steel were investigated through fracture surface topography analysis (FRASTA) and crystallographic orientation analysis. The hydrogen-related fracture morphologies of tempered martensitic steel were characterized by intergranular and quasi-cleavage transgranular fractures. FRASTA suggested that the hydrogen-related crack initiation site was inclusion and the crack propagated from quasi-cleavage fracture to intergranular fracture near the crack initiation site. In addition, crystallographic orientation analysis suggested that intergranular fracture propagated on prior austenite grain boundaries, whereas quasi-cleavage fracture propagated along {011} planes near the crack initiation site. However, quasi-cleavage fracture consisted of not only {011} planes but also various planes. These findings indicate that the fracture propagation path changed from the intergranular fracture on the prior austenite grain boundaries to the quasi-cleavage fracture along {011} planes and various planes caused by the cross slip in body-centered-cubic lattice within the prior austenite grains by the influence of inclusion.
11:30 AM Cancelled
Effect of Local Austenite-to-martensite Transformation on Hydrogen Embrittlement of Cold-rolled Medium Mn Steel: Jun Zhang1; Zhigang Yang1; Chi Zhang1; Hao Chen1; 1Tsinghua University
Luders banding is one of the local deformation behavior in cold-rolled medium Mn steel, during which local austenite-to-martensite transformation will occur under the condition of local strain and moderate austenite stability. Such local martensite transformation is expected to have great impact on the hydrogen embrittlement (HE) susceptibility, since a large amount of hydrogen will be inherited from austenite to martensite, i.e. one of the most sensitive phase to HE owing to its high density crystal defects. In this study, we compared the HE susceptibility of samples with similar austenite volume fraction and stability but different Luders strain in cold–rolled medium Mn steel. The propagation behavior of hydrogen-induced cracks, martensite transformation behavior and the local strain within the Luders band were fine characterized and the effect of local austenite-to-martensite transformation on the HE susceptibility was discussed.