Real structure of near-surface regions in austenite single crystals after implantation with 30 keV N + ions studied by synchrotron radiation under grazing incidence conditions

Abstract

Austenitic stainless steel single crystals (Fe 69Cr 16Ni 12) have been implanted with 30 ke V N + ions to doses of 3 × 10 16 and 3 × 10 17 N + cm -2 at a temperature of 273 K. The structure of the region close to the surface (within 1000A˚) was investigated by diffraction of synchrotron X-rays under conditions of grazing incidence and exit. The structural information is obtained from the distribution of Bragg intensities as a function of the exit angle at different angles of incidence, both angles being close to the critical angle for total reflection ( α c = 0.33δ). After implantation to 3 × 10 16 N + cm -2 the austenite is retained and the lattice parameter is increased by about 1%. After implantation to 3 × 10 17 N + cm -2 the austenite phase is completely transformed into at least three different nitride phases. The orientation of these nitrides shows a distinct correlation with the original austenitic matrix. From a comparison of depth-controlled grazing incidence diffraction data and model calculations we conclude that the ζ phase is created at the sample surface while the ζ phase is formed at depths greater than 500A˚.