Anisotropy of cold-worked Type-304 austenitic stainless steel: Focus on the hydrogen diffusivity

摘要

Anisotropic nature of effective hydrogen diffusivity was investigated on a cold-worked (CW) Type-304 stainless steel. The material was characterized by using disk-shaped specimens sampled from two directions of steel plates with various rolling ratio. The thickness direction of the disks was parallel to the rolling direction for SL specimens and perpendicular for LT ones. Electromagnetic induction (EMI) and electron backscatter diffraction (EBSD) clarified the content and distribution of strain-induced martensite (SIM). The effective diffusivities and solubilities were jointly determined by desorption method and thermal desorption analysis (TDA) in H-charged specimens with high-pressure gas. The increase of SIM with CW ratio and the differences of SIM distribution observed between LT and SL specimens could justify the anisotropic effective diffusivities. Finite element method (FEM) was used to simulate permeation tests based on multiple EBSD maps. Simulations supported the experimental findings: at the CW ratio of 60%, the CW process increased the diffusivity by twenty and the diffusivity was five time greater in the SL specimen than the LT one. The inhomogeneous SIM distribution justified the modifications of diffusion properties by CW in both specimens. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.