The effects of combined oxidation and carburization on the mechanical properties of Fe-9%Cr-1%Mo steels

The oxidation of Fe-9%Cr-1%Mo steels in high pressure CO2 produces not only a duplex oxide scale but also results in carburization of the metal which can raise the carbon content from the nominal 0.1% to in excess of 0.8%. The effects of this carburization on both tensile and creep behaviour has been studied using precarburized specimens and creep tests carried out in high pressure CO2. The tensile properties of carburized specimens at 753 K were similar to as-received and preaged specimens. The creep strengths of precarburized specimens at 773 and 798 K were slightly above that for uncarburized specimens. The results of combined creep-carburization tests at 873 K confirmed the relatively small effect of carburization on creep behaviour. (author)