Oxidation of chromium carbide coated Q235 steel in wet and dry air at 750 °C

Oxidation behavior of a PIRAC (Powder Immersion Reaction Assisted Coating) Cr23C6 coated Q235 steel is investigated in dry air and 18 vol.% O2 + 72 vol.% N2 + 10 vol.% H2O under 101,325 Pa (1 atm) with a flow rate of 3.0 cm s−1 at 750 °C. Results indicate the PIRAC Cr23C6 coating has good oxidation resistance with scarcely observed morphologies changes and weight gains after 10 h exposure. High temperature water vapor accelerates phase transform of Cr23C6 into Cr7C3. Difference in oxidants content of the two atmospheres and the followed carburization at the Cr2O3/Cr23C6 interface leads to difference in phase transformation of Cr23C6 into Cr7C3.