Abstract
Raman spectroscopy was applied to the study on the transient oxidation of the Fe-14Cr-0.4Mn-0.6Ti ferritic stainless steel in Ar gases at 1123K. It was found that in the thermal oxidation under low oxygen pressure, the minor alloying constitution of manganese and titanium resulted in the formation of thin oxide layers. During the early stage of oxidation, the double layer structure, which the outer and the inner were identified as MnCr2O4 and silicon oxide respectively, was formed on the grain of the substrate and Ti2O3 at the grain boundary. As a result of outer diffusion of titanium with reduction of Cr, Mn and Si oxides, the oxide layer produced for more than 600s showed mainly Ti2O3. In addition, the frequency shifts of Raman spectra showed that the compressive and tensile stresses existed in the oxide layers, MnCr2O4 and Ti2O3, respectively. These residual stresses in the oxide layers were released by the increase of porosity with oxidation time. It is shown that the frequency shifts of Raman spectra induced by residual stresses in the oxide layers reflect the low porosity of the oxide layers which results in the decrease of the metal dissolution in high temperature deaerated pure water at 488K.
