Influence of Cold Working on Hydrogen Diffusion Behaviour in an Austenitic Steel with Transformation-Induced Plasticity

Abstract

The main objective of this work was to obtain information about the hydrogen diffusion behaviour in a cold-worked austenitic stainless steel (X3CrMnNiMoN17-8-4) in which deformation-induced martensite formation occurs during mechanical deformation. Three different states of pre-deformation (31 %, 39 % and 49 %) that showed induced phase transformation from austenite to α’martensite as well as the solution-annealed material were part of this study. All samples were charged with hydrogen in a 0.1 M NaOH solution. This charging took place electrolytic with 10 mA cm-2 at three different temperatures (50 °C; 65 °C and 80 °C) in the double cell according to Devanathan and Stachurski. Due to the very slow diffusion of hydrogen through austenite, the samples were not charged until the equilibrium state was reached. To find out the necessary diffusion parameters, the data were fitted with numerical optimisation. Using this method, the effective diffusion coefficients of charging could be determined for all material states. The study also contains microscopic analyses to visualize the effect of cold working on the microstructure of the material. The appearance of α’-martensite significantly contributes to the susceptibility to hydrogen uptake leading to increasing diffusion coefficients in relation to higher pre-deformation.

Determination of Martensite Formation Rate by Magnetic In Situ Measurement in CrMnNi–N Steel

“…[20] One potential application for this austenitic stainless steel is welded pipes. First results on weldability and corrosion behavior have been published in Quitzke et al [21] and Hempel et al [22,23] For later application as welded pipe, martensite formation at various temperatures under increasing stresses and strains will be investigated. Using the kinetic model of straininduced α 0 -martensite formation by Olson and Cohen, [10] the evolution of the strain-induced martensite volume fraction can be described as a sigmoidal function.…”