Hydrogen embrittlement in the duplex stainless steel Z2CND2205 hydrogen-charged at 200°C

Physical and mechanical properties of austeno-ferritic stainless steels depend on the microstructure and phase transformations: many intermetallic phases, carbides and nitrides precipitate at different tempering temperatures. Hydrogen behaviour in steels is affected by the morphology and by the presence of precipitates, both for its diffusional behaviour and for the importance of trapping phenomena. In this paper, the hydrogenation of a 22Cr-5Ni duplex stainless steel has been achieved at 200°C in molten salts bath in potentiostatic conditions, and hydrogen embrittlement has been characterised using low strain rate tensile tests. The influence on hydrogen embrittlement of different intermetallic phases, carbides and nitrides has been considered via tempering heat treatment with tempering temperatures between 200 and 1050°C. The possibility of the recovery of the mechanical properties of charged steel outgassing at room temperature has been considered, investigating also the influence of different intermetallic phases, carbides and nitrides. Moreover, a new thermal technique based on high-temperature outgassing tests has been performed in order to calculate the hydrogen coefficient of diffusion.