EFFECT OF PROCESS PARAMETERS ON THE ATOMIC NITROGEN CONCENTRATION AS MEASURED BY CHEMILUMINESCENCE IN A POSTDISCHARGE NITRIDING REACTOR

In the present work, the nitriding process has been performed in microwave (2450 MHz) post-discharges. The operating conditions for the Ar-N2 and Ar-N2-H-2 post-discharges were a gas pressure in the range 3-100 hPa, a transferred h.f. power of 70-80 W and flow rate of between 300 and 2000 N cm3 min-1, giving a high gas velocity. The steel substrates were externally heated to reach the nitriding temperature. Quantitative results on atomic nitrogen concentration downstream from the microwave discharge have been obtained by NO chemiluminescence. This concentration has been studied as a function of the main process parameters. Correlation has been found between the atomic nitrogen concentration and the chemical composition and depth of the iron nitride layers growing on steel surfaces which are located in the post-discharge.