Surface cosegregation on Fe-3%V-C, Fe-3%V-C,N and Fe-15%Cr-N (110) single crystals

Abstract

Surface cosegregation has been studied on (110) oriented Fe-3%V-C, Fe-3%V-C,N and Fe-15%Cr-N single crystals applying AES and LEED. The surface compounds VC,V(C,N) and CrN are formed upon annealing in the temperature range from 450 to 750 degrees C depending on the alloy. The stoichiometries of the binary surface compounds correspond to VC(1.2) and approximately CrN(0.8) as determined by quantitative evaluation of Auger peak height ratios. The composition of the V(C,N) surface compound varies between V(C(0.6)N(0.6)) at 450 degrees C and V(C(0.2)N(1.0)) at 640 degrees C. Three-dimensional precipitates are not formed as indicated by Ar(+) depth profiling. After short annealing times streaking LEED patterns are observed indicating partial disorder in one direction of the direct space. Upon sufficient annihilation of surface defects sharp (4 x 1) patterns appear. A missing and added row "model" is proposed for the surface compounds on bcc(110) substrate surfaces.