“…In the following, these phases will be abbreviated by the small Greek letters defined in Table I. Diffusion of N and C, separately, in Fe and the corresponding nitrides and carbides has been studied thoroughly in the past. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] However, either upon nitriding or upon nitrocarburizing, as soon as the system contains C, which may already originate from the substrate (e.g., steel) and/or from the treatment medium (in case of nitrocarburizing), the role of this additional interstitially diffusing component C, next to the interstitially diffusing component N, has to be taken into account.…”