Effects of Austenitizing Temperature on Microstructure Evolution and Corrosion Resistance of High Cr Ferritic/Martensitic Steel

The effect of austenitizing temperature on microstructure evolution and corrosion resistance of the high Cr ferritic/martensitic steel was studied. The prior austenite grain size, martensite lath width and the size distribution of the second phase (Cr rich carbides) were observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The corrosion resistance of the steel was tested by electrochemical polarization curve. The results show that austenitizing temperature can affect the microstructure and corrosion resistance of the high Cr ferritic/martensitic steel. With the increase of austenitizing temperature from 950 degrees C to 1100 degrees C, the prior austenite grain size and martensite lath width of steel increase. The size of the second phase first decreases and then increases with the increase of austenitizing temperature, while its density first increases and then decreases. The electrochemical polarization curve confirmed that the corrosion current density of the steel first decreases and then increases with the increase of austenitizing temperature, and the corrosion rate showed the same change law as the corrosion current density, indicating that the corrosion resistance of the high Cr ferritic/martensitic steel first enhances and then deteriorates with the increase of austenitizing temperature.