Environmentally Assisted Cracking: Theory and Practice: Hydrogen Embrittlement
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
Monday 8:30 AM
February 28, 2022
Room: 201D
Location: Anaheim Convention Center
Session Chair: Reiner Kirchheim, Georg-August-Universität Göttingen; Ting Zhu, Georgia Tech
8:30 AM Invited
Contributions to the Understanding of Hydrogen Embrittlement by a Thermodynamic Approach: Reiner Kirchheim1; 1University of Goettingen
Fracture and deformation occurs by the formation, annihilation and motion of lattice discontinuities. Thus vacancies and dislocations cause plastic flow or new surfaces are formed during fracture. The energy of generating these discontinuities is decreased with increasing chemical potential of hydrogen as described the defactant concept [1]. Thus concentration of vacancies or density of dislocations is increased during plastic deformation in the presence of hydrogen. The same applies [2] to generating new surfaces (Hirth-Rice model). The motion of discontinuities may be increased despite solute drag, if discontinuities move by the formation of secondary discontinuities like kink pairs at dislocations. The thermodynamic concept is valid for all solutes; hydrogen is just a unique example of seeing and understanding the diversity of many chemomechanical effects including hydrogen embrittlement. [1] R. Kirchheim, Int. J. of Materials Research 100 (2009) 483-487[2] Kirchheim et al., Acta Materialia 99 (2015) 87–98
9:05 AM
Hydrogen-Induced Cracking of Pure Titanium in Hydrochloric Acid Solution Using Constant Load Method: Osama Alyousif1; 1Kuwait University
The hydrogen-induced cracking (HIC) of the commercial pure titanium (Ti) has been investigated as functions of applied stress and test temperature in hydrochloric acid solutions by using a constant load method. From the results obtained, HIC was hydrogen embrittlement (HE) related to the fracture of hydride. We have also found that the steady state elongation rate obtained from the corrosion elongation curve becomes a relevant parameter for predicting time to failure and a criterion to assess whether HIC takes place or not. A parameter, t_ss 〖t_f〗^(-1) was also found to be an indicator of whether HE takes place or not. Furthermore, it was deduced that HIC was qualitatively explained in terms of hydride formation and localized deformation, which was basically based on a hydride formation-rupture event at crack tips.
9:25 AM
Atomistic Study on Diffusion and Trapping of Hydrogen in Nanocrystalline Steel: Denver Seely1; Bradley Huddleston1; Nayeon Lee1; Sungkwang Mun1; Anh Vo1; Doyl Dickel1; Krista Limmer2; 1Mississippi State University; 2U.S. Army Combat Capabilities Development Command Army Research Laboratory
The local equilibrium of hydrogen (H) atoms in polycrystalline steel is analyzed using molecular dynamics (MD) simulations with a Modified Embedded Atom Method potential developed for the Fe-C-H system. MD is a powerful tool to provide information on the nanoscale distribution of H while experimental detection of H is limited. We examine hydrogen diffusion and trapping in a polycrystalline structure of tempered martensitic steel with ~1 million atoms composed of lath sub-grain boundaries, microvoids, solution carbon, and carbides. At 800 K, when hydrogen has higher mobility, hydrogen diffuses toward irregularities of those various trapping sites. The results show that within three ns, approximately 80% of total H are trapped in the vicinity of grain boundaries, and 10% of the atoms reside adjacent to solution carbon and carbides. This work provides comprehensive measures of high local concentrations of hydrogen at grain boundaries that could lead to hydrogen embrittlement fracture.
9:45 AM
A Surface Deformation Approach for Improved Hydrogen Embrittlement Resistance: Haoxue Yan1; Dylan Hall2; Jinwoo Kim1; S. Raima Mahmud1; David Dye2; C. Cem Tasan1; 1Massachusetts Institute of Technology; 2Imperial College London
To address hydrogen embrittlement (HE), there have been tremendous efforts in exploring microstructure design and surface coatings solutions. Here, we propose a different strategy based on changing the surface characteristics for improved HE resistance. Surface processing methods can create complex effects, altering subsurface microstructure and surface roughness simultaneously. While the high defect density beneath the deformed surface can hinder H diffusion into the bulk, increased surface roughness often leads to increased corrosion rate and diminished fatigue life. Interestingly, in our investigations, rough surfaces of commercial grade 316 stainless steel and Ti-6Al-4V suffered no susceptibility, whereas polished surfaces were found to suffer from HE and hydride growth during H charging. Here, we employed commonly available surface deformation techniques (e.g. sand blasting, peening) to carry out systematic investigations of surface roughness, subsurface defect density, H content, to test the limits of the proposed technique to elude HE.