The Role of Hydrogen on the Separation of Interfaces of  Supermartensitic Stainless Steel S13Cr

Abstract

This paper outlines experimental procedures and numerical analyses to research Hydrogen embrittlement (HE) of the supermatensitic stainless steel (SMSS) S13Cr submitted to different cathodic potentials. Hydrogen diffusion behavior was investigated by means of two electrochemical permeation techniques, namely the double potentiostatic method (DPM) and the step method (SM), and it was also performed thermal desorption spectroscopy (TDS) tests. Apparent Hydrogen diffusion coefficients vary from 1.4 x 10-13 m²/s to 4.7 x 10-12 m²/s and TDS reveals the existence of deep traps, such as interfaces of precipitates and between retained austenite and ferritic matrix. HE effects in terms of reduction of ductility were analyzed through tensile tests and fractographic analysis, where a maximum reduction of elongation of around 14% was measured and a majority of brittle fracture along entire net section was observed in test samples pre charged under -1.5 V/SCE and -1.7 V/SCE. A calculation procedure based on computational simulation via finite element method has been performed, in order to predict mentioned loss of ductility using the experimental data mentioned before. The computational model used a fracture-controlled method under static structural condition, which links reduction of elongation of tensile specimens to the decreasing of critical fracture energies, which, in turn, were achieved through a new mean field approach regarding thermodynamic excess variables. Herein presented observations make it possible to suggest, that S13Cr has good resistance to HE and that the mentioned calculation procedure is reliable, since slight deviations in the magnitude of 5% were observed.