NANOINDENTATION MEASUREMENTS OF AUSTENO-FERRITIC STAINLESS STEEL SUBMITTED TO HYDROGEN CHARGING

The changes of nanohardness as a result of cathodic hydrogen charging of austenoferritic stainless steel was investigated. As the hydrogen behaves differently in the ferrite (alpha) and austenite (g) phases, the hardness variation of both alpha and gamma grains before and after hydrogen charging were measured. The nanoindentation measurements using the Atomic Force Microscope were performed. Three various states of samples were examined: initial state, just after hydrogen absorption and after hydrogen desorption. It was shown that there are distinct changes of nanohardness between every state and each phase. Generally, the nanohardness of the gamma phase is higher than in case of the a phase. The increase of nanohardness of both phases after hydrogen absorption and its decrease after hydrogen desorption was observed and interpreted in terms of microstructural changes.