Magnetic and 57Fe hyperfine structural features of nitrided austenitic stainless steel

摘要: Abstract Samples of an austenitic stainless steel were plasma-nitrided at 673 K, for 4 h, in 80% H2−20% N2 gas mixture, different pressures: 4; 6 and 10 Torr. The samples characterized by four techniques: X-ray diffraction, Mossbauer spectroscopy, magnetic force microscopy energy dispersive X-ray. nitrogen concentration thickness the nitrided layer was found to be 7 at.% 2 μm 4 Torr-sample; those 10 Torr, 16 24 at.%, with nearly same thickness, namely 7 μm. These values are well correlated framework expanded austenite, as pointed diffraction data. data observed concentration, evidencing absence any domain patterns 6 Torr 10 Torr-samples quite similar, despite great difference their concentrations. 57Fe hyperfine parameters two sample depths assessed collecting distinct backscattering setup geometries. Fitting corresponding spectra model-independent field distributions, starting from very low values, allowed correlating find out that transition paramagnetic austenite occurs smaller fields than it is usually reported scientific literature. Such correlations point formation a submicrometer occurring on outermost surface sample. Despite complexity difficulties differentiating nitrides martensitic structure obtained 10 Torr pressures, results this work strongly indicate existence them layer.