Influence of hydrogen and microstructure on the fatigue behavior of duplex steels

  multicolor dices Representative volume elements of the duplex structure with different phase ratios, ferrite in red, austenite in blue. Left: 75% ferrite, 25% austenite; Middle: 50% ferrite, 50% austenite; Right: 25% ferrite, 75% austenite

Duplex steels are of interest for many applications, for example in offshore technology, owing to their extraordinary strength and toughness as well as their excellent corrosion resistance. Hydrogen embrittlement is affected by the microstructure of the components, and study of duplex steels provides the possibility of target microstructural optimization for a combination of austenitic and ferritic structural components.

The effect of hydrogen on the two phases structure in the duplex steels is complex and elusive. Based on different elastic-plastic property in each phase, there are pronounced internal stresses at the phase boundaries to greatly affect the hydrogen trapping and diffusion. Inhomogeneous stress distributions in cyclic loading will affect the hydrogen diffusion in duplex structure, which cause a cyclic time, together with global and local hydrogen concentration dependent fatigue behavior.

The aim of this project is therefore to gain an understanding of the interaction between material and loading history on the hydrogen embrittlement of duplex steels. Specifically, the hydrogen embrittlement in duplex steel 1.4462 will be quantified and analyzed experimentally on a microstructural size scale, along with numerical microstructure-sensitive models worked by the project partner at the HS Offenburg.

Reference:

M. Kreins, J. Wilkes, S. Wesselmecking, U. Krupp, in: Stahlinstitut VDEh (Ed.), Tagungsband Werkstoffprüfung 2021: Werkstoffe und Bauteile auf dem Prüfstand. Prüftechnik-Kennwert-ermittlung-Schadensvermeidung, 2021.

S. Schilli, T. Seifert, M. Kreins, U. Krupp, Materials Science and Engineering A (2021) 142030.