Modelling of room temperature outgassing and diffusion in a martensitic advanced high-strength steel

Hydrogen embrittlement (HE) is among the limiting factors for the employment of advanced high-strength steels in the automotive industry. One of the most relevant manifestations of HE for those components is delayed fracture. To perform HE risk assessment against delayed fracture in structural components wherein hydrogen accumulates near notches or bends after manufacturing or assembly, continuum models can be used to predict hydrogen diffusion and accumulation. To this aim, it is crucial to identify both the correct model parameters and boundary conditions (BCs). This study provides the required modelling and experimental framework to estimate the constitutive diffusion, trapping and outgassing parameters for a commercial martensitic advanced high-strength steel grade 1300. Permeation testing and simple room outgassing tests showed that a natural BC with one-parameter effectively reproduces the experimental results. The proposed model can be used to predict a reasonable hydrogen distribution, both inside of the component and near to the surface, which is valuable for HE risk assessments. Finally, the same BC can be employed with the interpretation of ex-situ hydrogen charged tensile tests.