Effect of hetero- and homo-nanostructure on the hydrogen embrittlement resistance in heavily deformed 316LN austenitic stainless steel

The heterogeneous and homogeneous nanostructured 316LN austenitic stainless steel with tensile strengths of approximately 1.8 and 2.0 GPa were fabricated by 92% heavy cold rolling and high-pressure torsion straining, respectively. The influence of heterogeneous and homogenous nanostructures on the resistance to hydrogen embrittlement was investigated. Thermal desorption spectroscopy of the electrochemical hydrogen-charged specimen showed that both nanostructures exhibited almost the same concentration of diffusible hydrogen. While the tensile properties of the homogenous nanostructure were severely affected by the diffusible hydrogen, it had less impact on the tensile properties of the heterogeneous nanostructure. The difference in the embrittlement behavior between the heterogeneous and homogeneous nanostructures is attributed to the mechanism of crack growth observed by tensile fractography. Hydrogen embrittlement is suppressed in the heterogeneous nanostructure because crack growth is hindered by twin domains. The crack easily initiates in the homogeneous nanostructure and the resistance to crack growth is low. Graphic abstract: [Figure not available: see fulltext.]