Optical emission spectroscopy of DC pulsed plasmas used for steel nitriding

Optical emission spectroscopy of atomic lines and molecular vibrational bands in N2, H2/N2 and Ar/N2 plasmas at steel nitriding conditions have been reported as an application of this diagnostic to plasma nitriding. An increase in Ar I intensity as Ar percentage increases in an Ar/N2 mixture is observed, while the effect on N2+ emission has a decrease, just the reverse of Ar I emission profile. As electron energy distribution function, EEDF, shifted to high electron energy as Ar percentage increases in the mixture, the presence of high-energy electron at high gas temperature of discharge can be predicted. It has also been found that pressure effect on N2+ band in pure nitrogen plasma is to increase the band intensities. Spatial distribution of N2+(0,1) and N2+(0,2) emission profile in N2/H2 mixture reveals shrinking of negative glow by 10 mm in the presence of 10% H2 and 90% N2 relative to a pure N2 plasma.