The characteristic surface segregation of both impurities as well as major alloy constituents in 21Cr–6Ni–9Mn (21–6–9), a nitrogen strengthened austenitic stainless steel, has been studied using scanning Auger microscopy (SAM), x‐ray photoelectron spectroscopy (XPS), and sputter Auger techniques. Segregation effects were examined for polycrystalline material heated to temperatures ranging up to 800° C. The SAM results show both a nonuniform spatial distribution of the various segregating species, as well as a strong cosegregation of boron with nitrogen at temperatures above approximately 700° C. Based on a bulk concentration of less than 10 ppm, the resulting surface‐to‐bulk concentration ratio for boron is greater than approximately 5×104. Both the boron and nitrogen Auger and XPS spectra associated with commercially available boron nitride material are identical to those obtained from the segregated layer on 21–6–9 and indicate that the boron and nitrogen cosegregate to form a boron nitride surface layer. This segregated BN layer, which initially is formed at high temperatures and uniformly covers the surface after one hour of heating, is found to be stable down to room temperature. The observed Auger peak positions are compared with semiempirically calculated values based on the XPS results.