Effect of dew point on the surface selective oxidation and subsurface microstructure of TRIP-aided steel

In this work we examined the effect of dew point on the surface selective oxidation behavior and the subsurface microstructure of TRIP-aided steel mainly by XPS and FE-SEM. It is shown that the variation of the dew point changed the morphology and chemical composition of the surface oxides. Furthermore, as the dew point increased, ferrite was found in the subsurface region of TRIP-aided steel. Considering the severe degree of internal oxidation, decarburization and consumption of minor alloy elements are proposed to be responsible for this ferrite band.

► Increase of dew point changed the morphology and the chemistry of surface oxides.
► Increase of dew point changed the subsurface microstructure from ferrite + austenite to single ferrite at high temperature.
► The formation of subsurface ferrite band modified the surface segregation and selective oxidation of the alloying elements.
► The internal oxides have no significant pinning effect on the subsurface ferrite growth during annealing.