Investigation of the compound layer formed by steel 16MnCr5 after gas nitriding

The aim of this research is the investigation of the compound layer formed by steel 16MnCr5 after gas nitriding. The investigation was carried out with metallographic methods – that is, with optical microscopy and electron probe microanalysis (EPMA). The thickness of the compound layer was measured using optical microscopy. The profile of nitrogen (N) concentration was determined using a Jeol JXA-8900 RL microanalyzer. The conditions of the EPMA investigation were a potential U = 20 kV and a distance of 5 μm between two nearest points. The thickness of the compound layer for all the samples was measured with an optical microscope. Based on the results, the kinetics of the compound layer and the activation energy were calculated, recognizing the growth law of the layer. The results of EPMA demonstrate the presence of two phases, ϵ (Fe₂N_(1+x)) and γ′ (Fe₄N), which contain nitrogen.