Fig. 6. (a) Spectrum of the glow discharge during low-temperature plasma carburizing,
(b) Detail of spectral lines of the glow discharge for gas mixture of 0.25%, 0.50%, 0.75%
and 1.00% CH4 in 80% H2+20% Ar. Samples kept at 723 K, gas mixture flow rate of
1.67×10−6Nm3 s−1 and pressure of 400 Pa.