Surface segregation of antimony on ferritic single crystals

Antimony has frequently been reported to cause temper embrittlement induced by grain boundary segregation in steels containing both nickel and chromium. In order to study the interdependent segregation behaviour of antimony and nickel and the effect of chromium on segregation of these elements, surface segregation was studied on Fe–25% Cr–2%Ni–0.15%Sb and Fe–2.5%Si–2%Ni–0.15%Sb single crystals. Segregation was investigated by means of Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) in the temperature range between 500 and 650°C. On Fe–25%Cr–2%Ni–0.15%Sb, segregation of antimony leading to surface saturation and cosegregation of nickel are observed on (100), (110) and (111) oriented surfaces. LEED investigations yield a complex domain structure which can be derived from a c(2×2) pattern for the (100) oriented surface and a (1×1) pattern for the (111) oriented surface. On the (110) oriented surface, reconstruction occurs. On Fe–2.5%Si–2%Ni–0.15%Sb, the investigated (100) oriented surface is also saturated with segregating antimony. Cosegregation of nickel occurs, but is weaker than on the crystal containing chromium; thus, chromium intensifies cosegregation of nickel with antimony. The LEED pattern exhibits a complex domain structure which is very similar to the structure observed on the (100) oriented surface of the crystal containing chromium.