Mesoscopic model of hydrogen embrittlement in particle strengthened materials

ABSTRACT

This work focuses on the constitutive modelling of damage development in particle strengthened materials in the presence of hydrogen. We apply the model to an area at the interface of a dissimilar weld of 8630 steel/IN625 nickel alloy which is known as the ‘featureless region’. This region contains an array of $M_7{C}_3$ carbides each measuring about 40 nm. Cleavage-like fracture has been observed only in the presence of hydrogen and it is attributed to a combination of two types of hydrogen embrittlement mechanisms: hydrogen-induced decohesion (HID) along the $M_7{C}_3$-matrix interface of and a ductile-type fracture (Hydrogen Enhanced Local Plasticity, HELP). Modelling the constitutive behaviour of this region at a continuum level is not appropriate as the major role in the material response is the interaction of the carbide particles with dislocations which is captured at the mesoscopic level. Here we propose a constitutive model of the ‘featureless zone’ that accurately represents the effect of hydrogen on the constitutive response of the $M_7{C}_3$ region at the mesoscopic scale. Hydrogen enhances the evolution of dislocations around the $M_7{C}_3$ carbides, therefore the stress locally increases affecting the interfacial strength. The result is that, in the region of high hydrogen concentration, the material exhibits softening.

KEYWORDS:

• Hydrogen embtittement
• mesoscopic model
• particle strengthened materials
• damage evolution
• hydrogen diffusion

Acknowledgments

This research was supported by the EPSRC through the HEmS Programme Grant EP/LO/4742/1.

O.B would like to acknowledge the European Union's Horizon 2020 – EU.1.3.2. – Nurturing excellence by means of cross-border and cross-sector mobility under the Marie Skłodowska-Curie individual fellowship MSCA-IF-2017, MetaBioMec, Grant agreement ID: 796405.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) through the HEmS Programme Grant Number EP/LO/4742/1