Oxidative corrosion behavior of 321H stainless steel in high-temperature carbon dioxide

This study explored the oxidation behavior of 321H stainless steel oxidized at 650 °C for 2000 h. The oxidation kinetics, oxide scale morphology, oxide types, and element distribution of 321H stainless steel under this condition were explored through oxidation mass-gain curves, scanning electron microscopy, X-ray Diffraction, and transmission electron microscopy. The results showed that during the initial 5 to 10 h of oxidation, a relatively dense Cr-rich oxide layer (mainly Cr 2 O 3 ) was formed on the surface of the specimens, and the specimens showed exhibited excellent oxidation resistance with a markedly reduced oxidation rate. However, after 10 h, the Cr-rich oxide layer rapidly peeled off and caused a large amount of Fe elements to be externally oxidized to form loose Fe 3 O 4 , resulting in a rapid increase in the oxidation rate. After 200 h of oxidation, the specimens underwent significant inner oxidation to form a fine, dense spinel layer with the chemical composition of Fe 3- x Cr x O 4 , which can effectively block the diffusion of CO 2 and reduce the oxidation rate again.