1992 Volume 33 Issue 6 Pages 571-576
The purpose of this work is to detect and quantify nitrogen which is dissolved in steels using parallel detection Electron Energy Loss Spectroscopy (PEELS). PEELS in the Transmission Electron Microscope (TEM) has a high detection efficiency and is potentially powerful for studying the behaviour of light elements in commercial steels with a high spatial resolution.
Type 316 stainless steels (SUS316) and high nitrogen austenitic stainless steels having a range of nitrogen (0.04–0.40 mass%) content were used. We also used a duplex stainless steel as a test specimen where partitioning of nitrogen between ferrite (α) and austenite (γ) phases was present. Typically nine spectra were recorded from the same area of the specimen and then were processed using the iterative averaging method described. This method efficiently removes the noise due to the channel gain variation in the parallel detection and allows the detection of small peaks. The intensity ratios of (IN⁄ICr) or (IN⁄IFe) are correlated with the atomic concentration ratios (CN⁄CCr) or (CN⁄CFe) where I and C denote the intensity and atomic concentration, respectively.
The measured intensity ratio and the concentration ratio have a good correlation and a common calibration curve is obtained regardless of the matrix composition which are different between type 316 and high nitrogen austenitic stainless steels. By using the calibration curve, the nitrogen content can be determined as 0.26±0.04 mass% in the γ-phase of the duplex stainless steel, while that of α-phase is close to or below the detection limit of 0.04 mass%.
