Effect of pulsed current on cathodic cage plasma nitriding of non-alloyed steel

The cathodic cage plasma nitriding (CCPN) is an efficient and cost-effective surface modification technique, extensively used in last two decades. The effectiveness of CCPN is dependent on several control parameters and the objective of current research is to examine the effect of pulsed current on CCPN efficiency. The samples of non-alloyed steels are nitrided in fixed processing conditions while using variable pulsed current. The processed samples are analyzed by micro-hardness test, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS) and ball-on-disc wear tester. The corresponding plasma parameters (such as electron temperature and nitrogen active species generation) are analyzed using optical emission spectroscopy (OES). The hardness and wear resistance is found to be significantly enhanced by increasing the pulsed current. The processed samples contain iron nitrides phases (Fe3N, Fe4N), whose intensity increases with increase in pulsed current. The results from surface analysis show a good correlation with the results obtained from OES. This study clarifies the contribution of pulsed current on the nitriding performance and plasma reactivity in CCPN system in a comprehensive manner. The results are compared with the previous reports on various systems.