Oxidation of a Mn‐Cr austenitic steel during creep testing and its interaction with the fracture

Abstract

The interaction between oxidation and creep rupture was studied in a 17 Mn‐10 Cr austenitic steel, of interest as structural material for the internal components of fusion reactors. The observation of the creep specimens tested in air at temperatures ranging from 773 to 973 K revealed the presence of an adherent oxide scale and of a ferritic phase underneath, which forms as a consequence of the Mn depletion of the austenitic matrix. The microstructure of the two layers was investigated by optical microscopy, SEM, X‐ray diffraction, EDS and magnetic permeability measurements. The scale has a complex structure, being composed mainly of manganese oxide. The ferritic layer is completely recrystallized and does not present grain boundary precipitates as the austenitic phase does. The effect of the surface modification on the creep rupture process is discussed in the light of a recent model of deformation‐oxidation interaction.