In-situ characterization of the oxide scale formed on yttrium-coated 304 stainless steel at 1000 °C

In-situ X-ray diffraction was combined with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses to characterize the oxides formed on yttrium-coated 304 stainless steel during oxidation at 1000 °C in air. Results are compared with those obtained on uncoated specimens. Care has also been taken on the structural transformations during the cooling process. At 1000 °C, yttrium leads to the formation of YCrO3 and YCrO4 oxides. These oxides are mainly located at the external interface. Moreover, silicon segregation at the oxide–metal interface is also observed. The yttrium coating seems to promote a favorable effect on the continuity of the silicon-rich subscale limiting the oxide scale growth and the formation of iron oxides. Thermogravimetric studies reveal that yttrium addition leads to a lower weight gain which is related to a limitation of the initial transient oxidation stage and to a reduction of the parabolic rate constant.