Critical assessment of the evaluation of thermal desorption spectroscopy data for duplex stainless steels: a combined experimental and numerical approach

Abstract The present study evaluates thermal desorption spectroscopy (TDS) data measured for UNS S32205 duplex stainless steel. Variations in the TDS spectra are obtained by electrochemical hydrogen charging for different times and by applying different heating rates for desorption to evaluate the desorption activation energy. Good agreement is found when comparing the experimental TDS curves with the desorption flux based on a numerical diffusion model using a homogeneous average hydrogen diffusion coefficient for the two-phase (ferrite-austenite) duplex microstructure. Trapping cannot be distinguished from the experimental TDS data since hydrogen diffusion in austenite is the rate-determining process during desorption. An average diffusion activation energy of 43.4 kJ/mol is determined from the experiments. Moreover, similar findings are obtained with a finite-element model that includes the heterogeneous hydrogen-related properties of the two phases of this duplex stainless steel.