University of Cambridge > > Engineering Department Mechanics and Materials Seminar > Assessing the contribution of hydrogen-deformation interactions to hydrogen-induced intergranular fracture in nickel-base alloys

Assessing the contribution of hydrogen-deformation interactions to hydrogen-induced intergranular fracture in nickel-base alloys

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Despite over a century of study, hydrogen-induced premature failure of structural metals continues to negatively impact critical industries spanning the aerospace, marine, transportation, and energy sectors. Efforts to mitigate this deleterious effect are undermined by an incomplete understanding of the microscale processes governing hydrogen-induced degradation. Recent literature posits that the governing mechanism for hydrogen-induced intergranular failure is the decohesion of grain boundaries principally driven by hydrogen-deformation interactions. However, there is a lack of experiments which quantitatively establish the predominant contribution of hydrogen-deformation interactions to hydrogen-induced intergranular cracking. Additionally, the extension of such mechanisms into more complex, industrially-relevant alloys is hindered by the uncertain contribution of alloy metallurgy to hydrogen-induced degradation.

The objective of this presentation is to review two research activities at the University of Virginia which sought to understand the contribution of hydrogen-deformation interactions to hydrogen embrittlement susceptibility in nickel-base alloys. The first half of the talk outlines recent experiments that aimed to quantitatively evaluate the influence of mobile hydrogen-deformation interactions on hydrogen-induced intergranular cracking in polycrystalline nickel. The results of this effort quantitatively demonstrate that, while mobile H-deformation interactions do contribute to hydrogen-induced intergranular fracture, this contribution can be considered secondary in nature. The second half of the talk describes our initial efforts to evaluate the effect of hydrogen on the deformation behavior of a precipitation-hardened nickel-base alloy as a function of aging condition. Transmission electron microscopy, coupled with the analysis of work hardening behavior, indicates that hydrogen induces a transition from particle shearing to bypassing at smaller particle sizes. Moreover, counter to previous findings in polycrystalline nickel, evidence of increased propensity for cross-slip is also observed in the presence of hydrogen for these precipitation-hardened alloys. The talk then concludes with a brief overview of ongoing experiments seeking to understand the effect of these bulk deformation results on the processes occurring within the fracture process zone.

This talk is part of the Engineering Department Mechanics and Materials Seminar series.

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