SURFACE COSEGREGATION OF CHROMIUM AND SULFUR IN SINGLE CRYSTALLINE AUSTENITICFe–Ni–CrALLOYS

In this work we have studied cosegregation of sulfur and chromium on well-defined austenitic Fe–Cr–Ni alloy surfaces. For this purpose we have investigated (100)-oriented surfaces of Fe–14.8%Cr–17.8%Ni(cS=9 wt-ppm) and Fe–18%Cr–14%Ni (cS=18 wt-ppm) single crystals using Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). Segregation experiments were carried out under UHV conditions at temperatures ranging from 500 to 900°C. Cosegregation of chromium and sulfur is very pronounced on the Fe–14.8%Cr–17.8%Ni(100) alloy surface, while on Fe–18%Cr–14%Ni(100) the surface concentration of cosegregated chromium is rather small. On both surfaces sulfur segregation is characterized by a c(2 × 2) LEED pattern. The results of the present study are compared with a previous study using ferritic Fe–15%Cr–S(100) alloy single crystals.