A study of impurity segregation to the surface of an austenitic stainless steel using Auger electron spectroscopy

The object of this work is to study the segregation of elements such as chromium, phosphorous, sulphur and nitrogen to the surface of an austenitic stainless steel made by UGINE (France). The Investigation is carried out by in-situ annealing inside the ultra-vacuum chamber of an Auger electron spectrometer (AES). The specimens are initially homogenised by an anneal at 1050C inside evacuated silica capsules. They are then introduced inside the vacuum chamber of the AES where they are first of all activated, at room temperature, by ionic bombardment and then heat treated at various temperatures ranging from 600 °C to 900°C. The results are obtained in the form of AES spectra recorded in the differential mode. It is found that the surface of the material undergoes alterations, some of which are temporary and others durable. These alterations are : co-segregation of nitrogen and chromium, segregation of sulphur and competition between nitrogen and sulphur and between phosphorous and sulphur. The driving force of segregation is in the following order : S > P > N.