EMISSION-SPECTROSCOPY OF THE PLASMA IN THE CATHODE REGION OF N-2-H-2 ABNORMAL GLOW-DISCHARGES FOR STEEL SURFACE NITRIDING

Plasma analysis using emission spectroscopy has been carried out in th e cathode fall and the negative glow of N2-H-2 abnormal glow discharge s for steel surface nitriding. The spatial distributions of the select ed excited states of N2, N, N2+, N+, NH, H-2, H and Fe have been measu red in terms of their dependence on the main process parameters, such as the cathode temperature (400-550-degrees-C). H-2 percentage in the gas mixture (10-70%) and total pressure in the nitriding reactor (400 and 800 Pa), corresponding to the given values of the discharge curren t (115-260 mA) and applied voltage (465-635 V). The experimental data presented yield reliable information on the occurrence of excited stat es in the cathode region and on the effect of the process parameters o n the cathode fall thickness, which determines the energy distribution s of ions bombarding the cathode and is an important input parameter i n plasma process modelling.