Segregation and morphology on the surface of ferritic stainless steel (0 0 1)

The temperature dependence of the segregation and morphology of ferritic steel (0 0 1) surfaces has been examined by a combination of Auger electron spectroscopy, low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and low-energy electron loss spectroscopy. Upon annealing ferritic steel at 500 °C, the topmost layer was observed to be mainly composed of Fe–Cr alloy. Oxygen segregation was also detected locally in the STM images. LEED showed a (1 × 1) pattern and a weak (√5 × √5)R27° reconstruction corresponding to Fe and Cr4O5, respectively. Upon annealing at 600 °C, carbon and chromium co-segregated to the surface, forming two different regions composed of CrC and Cr-based steel, while the Cr4O5 domains disappeared. Upon annealing at 700 °C, nitrogen segregated to the surface, and the topmost layer was observed to be mainly composed of CrN domains with local CrC domains.