The effect of microstructure on the oxidation and carburisation of 9Cr-1Mo steel exposed to CO₂

To understand the effect of microstructure on the oxidation characteristics of 9Cr-1Mo steel, experimental material with two different starting microstructures (ferritic and martensitic) were exposed to a CO₂ rich atmosphere at 600 °C and 640 °C for up to ∼7000 hours.

The microstructure influences the size and distribution of carbides forming within the 9Cr-1Mo steel exposed to a CO₂ rich atmosphere. These differences lead to elemental segregation during carburisation and oxidation. This elemental segregation influences the oxidation characteristics of the 9Cr-1Mo steel and the morphology of the internal oxidation zone, and subsequently the spinel structure shows ghosts of the prior substrate microstructure.