Effects of Heating Rate on Austenitic Transformation and Corrosion Property of High Chromium Ferritic/Martensitic Steel

The effect of heating rate on austenitic transformation and corrosion resistance of the high Chromium (Cr) ferritic/martensitic steel was studied. The grain size was observed by optical microscope (OM), the distribution of second-phases was observed by transmission electron microscope (TEM), and the thickness and phase composition of corrosion products were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The results show that the heating rate can affect the austenitic transformation and corrosion resistance of the high Cr ferritic/martensitic steel. As the heating rate increases, the austenitic transformation time of the steel is suppressed, and the grain size of the steel decreases and the number of second- phases increases. Electrochemical polarization curves confirmed that with the increase of heating rate, the corrosion potential of steel sample decreased and the corrosion current increased, which indicates that the corrosion resistance of the high Cr ferritic/martensitic steel was deteriorated. In addition, there was no significant difference in the phase composition of the corrosion products after the immersion test. The thickness of corrosion products measured by SEM was in consistent with the results of electrochemical polarization curves.