Nitriding is a thermochemical surface treatment, by which nitrogen is introduced from an outer gas atmosphere, plasma, or salt bath into the surface adjacent regions of a component [1]-[3]. The nitrogen absorbed at the surface will diffuse inwardly leading to the development of the so-called diffusion zone. At sufficiently high chemical potential of nitrogen in the nitrogen-donating medium (the "nitriding atmosphere"), iron may react directly with nitrogen leading to the development of a layer of iron nitride(s) on the specimen surface, the so-called compound layer, on top of the diffusion zone. This layer is generally composed of grains of γ'-Fe_4N_(1-x) and ε-Fe_3N_(1+x) [2].
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