Hydrogen embrittlement of Cr-Mn-N-austenitic stainless steels

Cr-Mn-N austenitic steels show a unique combination of properties, i.e. high strength, high ductility, non magnetic and good corrosion resistance at costs being much lower compared to Cr-Ni austenitic steels. Hydrogen environment embrittlement (HEE) was investigated by slow displacement tensile testing in hydrogen atmosphere at 10 MPa and −50 °C. The fracture appearance of stable Cr-Mn-N austenitic steels with lower Mn contents (12Mn-0.7N) was transgranular whereas higher Mn contents (18Mn-0.7N) resulted in twin boundary fracture. This change in fracture morphology was related to a modest change in macroscopic ductility. Such fracture behaviour is similar to what is known from metastable Cr-Ni austenitic steels, therefore, Mn and/or N cannot be used to replace Ni in stable austenitic high HEE resistant steels.