Modelling hydrogen migration and trapping in steels

摘要

Hydrogen embrittlement remains of critical concern in the design of strong and reliable microstructures in steels. The role of microstructure in susceptibility to hydrogen trapping is evaluated using a numerical thermokinetic simulation approach. The simulation scheme is applied to evaluate variations in dislocation density and grain size in pure ferritic iron, ferritic and martensitic low alloy steels during cooling and ferritic steels under deformation. Additionally, variations in NbC nanoprecipitates in low alloy tempered martensitic steel, and coherent and incoherent TiC precipitates in low alloy steels were evaluated. These simulations were conducted to quantify the influence of such features on the trapping efficiency of interstitial hydrogen. To simulate the diffusion process in a complex microstructure, a mean field approach is applied. Modelling approaches adopting physically based formulations for the calculation of the trapping-affected concentration of hydrogen in the lattice are suggested, adopted in the present calculations and validated for a wide range of experimental and microstructural conditions. The combination of thermokinetic simulations with hydrogen trapping behaviours is the first of its kind and presents a means to incorporate the effects of various microstructural features, with respect to hydrogen migration and trapping, in the design of hydrogen embrittlement resistant steels. (C) 2016 Elsevier Ltd. All rights reserved.