Modelling and simulation of hydrogen redistribution in a heterogeneous alloy during the cooling down to 200 °C

Modelling of hydrogen induced pressurization of internal cavities

“…This redistribution is driven by the evolution of solubility within both phases as previously described in Ref. [26].…”

“…A physical model of hydrogen redistribution in a heterogeneous material as a function of temperature based on diffusion equation and taking into account solubility and diffusivity variations with temperature as well as composition dependent phase transformation has been proposed in our previous paper [26] in order to estimate both the redistribution of hydrogen between the matrix and the segregation band and to calculate pressure increase in the cavity hold at 200 C, i.e. before hydrogen outgassing in a manufacturing process.…”

“…In order to conduct these simulations, the diffusive properties of the heterogeneous alloy and related data have been taken from Ref. [26]. Based on process guideline of such components, a 30 Ch À1 cooling rate was applied and the initial amount of hydrogen was taken to be equal to 1 wt ppm corresponding to the maximal admissible concentration of hydrogen usually encountered during such processes.…”

“…Consequently, the diffusion and desorption of hydrogen into the cavity together with the estimation of the transient redistribution of hydrogen and resulting pressure build up within the cavity during the thermal treatment will be solved by using the model proposed in Ref. [26] which better fits the present context. This model based on Finite Difference Method has been proposed in order to estimate the transient redistribution of hydrogen in heavy components such as pressure vessels.…”

“…This approach is then correlated to the typical industrial thermal cycle to elucidate the maximal expected pressure reachable in aforesaid context by using the diffusion-desorption procedure proposed in Ref. [26]. The related kinetic effects caused by mass diffusion and leading to a dynamic redistribution of hydrogen within the component during cooling will also be analyzed.…”