F2-6 A Finite Element Analysis of Hydrogen Diffusion in a Stainless Steel Containing Strain-Induced Martensite

Abstract

Hydrogen can affect drastically the mechanical properties of stainless steels by the so called Hydrogen embrittlement. It is crucial to be able to describe the hydrogen content in the material especially at the microscopic scale. The diffusion process is depending on the fugacity of hydrogen on the surface, on the diffusivity and solubility in the bulk of the material. In the case of metastable austenitic stainless steels, strain-induced martensitic transformation modifies the diffusion process since the martensite and austenite have different solubilities and diffusivities. It is experimentally impossible to observe in situ and locally the diffusion process. Only the simulation is able to describe the diffusion at the microscopic scale in presence of two different phases. This work presents the finite element simulation of hydrogen diffusion in a model of microstructure corresponding at the microscopic scale to the real microstructure of a cold-rolled stainless steel. The spatial distribution of the different phases is obtained by the EBSD technique. From the phase map and some image analysis, a model is built and meshed for diffusion simulation. The drastic effect of the presence of martensitic domains on the hydrogen transport in the bulk of the material is clearly shown.