High quality iron nitrided layers have been obtained by using flowing microwave post-discharges in Ar-N2-H2-CH4 mixtures.
The afterglow is characterized by emission of spectral bands from N2 (B,V’ = 11-8) and CN (B,V’ = 7) radiative states, resulting from N + N and C + N recombination reactions, respectively. The N and C atom densities have been determined by NO titration for N atoms and from band intensities of the spectra emitted by the N + N and C + N reactions. In conditions of 40 Torr - 120 watts, 2.45 GHz discharges with Ar - 11% N2 - 5x103CH4, it has been deterinined [N] — 5x10-15 cm-3 and [C]~ 1013 cm-3 at a time aí 10-1 sec. in the post discharge.
With such N and C atom densities in the post-discharge, thick e - Fe2-3 N coatings (20-22 ?m) have been produced, without oxide layers, for treatment times of 3 hours and a substrate temperature of 5500 C.
