A Comprehensive Study of Hydrogen Redistribution and Embrittlement Prevention in Ferrous Alloys

Abstract

Hydrogen may cause severe degradation on some high strength alloys, and due to their technological and economic relevance, research efforts have intensified in recent years to improve our understanding of such phenomena. A physical model of interstitial element diffusion has been used to study the fluxes of hydrogen during manufacturing of metallic alloys. In particular, the present model contemplates diffusion in its most comprehensive description, i.e. atom diffusion is driven by the gradient in chemical activation, instead of simply occurring down the composition gradients. The model incorporates the influence of thermal history, microstructure, matrix solubility, multiple trapping distributions, and interaction with the atmosphere. This model is able to describe and predict the behaviour of hydrogen during standard industrial practices, and it has been used to explain the effect of component size, cooling rate, microstructure, deformation level, dislocation distribution, grain size, carbide presence and distribution, phase transformation temperature, baking conditions, etc. on hydrogen redistribution. Furthermore, by estimating possible supersaturation at specific regions in the component, it allows to anticipate defect formation and embrittlement risk (and therefore, to prevent them). Not only that, but by using this model, a method has been developed which enables to reduce hydrogen content from the metal via the use of imposed temperature gradients. This method has recently obtained several patents.