Nature of boron and nitrogen superficial “segregation” on the FeNi 36 alloys

Abstract

In a recent paper, the authors reported the parameters of sulfur bulk diffusion in a Fe-Ni 36 alloy. They were determined by the exploitation of the superficial segregation kinetics obtained by AES studies. The authors have also reported that neither boron nor nitrogen are observed on the free surface of the as received alloys during the various heat treatments up to 1000{degrees}C, but they are observed in the 600--900{degrees}C range, if the material is prior annealed at 1000{degrees}C. The boron and nitrogen elements are shown to cosegregate on the free surface and the observed energy shift (7 eV) of the auger boron peak suggests a strong binding of this element. When the annealing temperature approaches 900{degrees}C these elements disappear from the surface leaving only sulfur strongly segregated at all temperatures studied. Otherwise, working on the Ni{sub 3}Al, another research effort interpreted the boron behavior as indicating that it tends to segregate only to the defective free surface (after ion bombardment) and attribute the absence of boron on the well annealed surfaces to the highly ordered nature and good crystallinity of the near surface regions. The purpose of this paper is to clarify the nature of the superficial cosegregation of boronmore » and nitrogen and the surface layer on the Fe-Ni alloy using AES results and according to Fowler's thermodynamic model.« less