Grain-boundary engineering markedly reduces susceptibility to intergranular hydrogen embrittlement in metallic materials

Abstract

The feasibility of using "grain-boundary engineering" techniques to reduce the susceptibility of a metallic material to intergranular embrittlement in the presence of hydrogen is examined. Using thermomechanical processing, the fraction of "special" grain boundaries was increased from 46 to 75% (by length) in commercially purity Nickel samples. In the presence of hydrogen concentrations between 1200 and 3400 appm, the high special fraction microstructure showed almost double the tensile ductility; also, the proportion of intergranular fracture was significantly lower and the Jc fracture toughness values were some 20 to 30% higher in comparison with the low special fraction microstructure. We attribute the reduction in the severity of hydrogen-induced intergranular embrittlement to the higher fraction of special grain boundaries which reduces the crack initiation site density.

Measurement and Modeling of Hydrogen Environment-Assisted Cracking in Monel K-500

“…[2][3][4][5][6]10,24,25,31,32] Metallurgical candidates include cold work prior to aging resulting in high hardness, alloy composition variation, grain boundary carbide/graphite, segregated impurities such as S, P or Se, [18] and grain boundary misorientation. [33] Investigation of the metallurgical factors which govern HEAC is outside the scope of the present study, but the approach reported here will inform such future work.…”

The dual role of coherent twin boundaries in hydrogen embrittlement

“…Previous work on pure Ni showed that increasing the fraction of low-S boundaries reduces HE susceptibility 18 . Our study reveals a more subtle relationship between microstructure and HE: low-S boundaries and, most surprisingly S3 CTBs, play a dual role in H-assisted fracture.…”

Hydrogen embrittlement of grain boundaries in nickel: an atomistic study

“…1 Hydrogen in metallic containment systems, such as high-pressure vessels and pipelines can cause the degradation of their mechanical properties that can further result in a sudden and unexpected catastrophic fracture. [2][3][4][5] A wide range of hydrogen embrittlement phenomena was attributed to the loss of cohesion of interfaces (between grains, inclusion and matrix, or phases) due to interstitially dissolved hydrogen. 6 This concept and related models, [7][8][9] however, have not been made sufficiently predictive due to a lack of fundamental understanding of the chemomechanical mechanisms of embrittlement, despite considerable research effort.…”