Correlations between active species density and iron nitride layer growth in Ar-N₂-H₂microwave post-discharges

Correlations are demonstrated between the production of N, H and NH active species in an Ar-N 2 -H 2 microwave flowing post-discharge and the thickness of epsilon and gamma ' layers on a pure iron substrate. The Fe 2-3 N, epsilon -layer thickness increases with N atom density when oxide layers are simultaneously removed by H atoms. A maximum has been found in the post-discharge reactivity when the H 2 /N 2 density ratio is in the 10 -3 -10 -2 range.