Morphology and phase analysis of nitride layer on pure iron

The pure iron sample was treated using gas nitriding at 1000 °C for 1 hour. The morphology and phase analysis of the nitride layer was characterized by scanning electron microscope and X-ray diffraction. The thickness of the nitride layer and average grain size were derived from the scanning electron microscope micrograph. The crystallite size was determined by X-ray diffraction using the Williamson-Hall method. The micrograph from the scanning electron microscope showed a nitride layer, a diffusion zone, and a narrow gap between them. The thickness of the nitride layer was 8.1 ± 0.5 µm with a visible gap in the diffusion zone of 1.5 ± 0.5 µm. The grain size in the diffusion zone increased, and some interstitial to the iron lattice and/or precipitate at the grain boundary were observed. The phase analysis of the nitride layer showed a single phase ε-Fe2N with a crystallite size number of 549 Å.