Investigation Corrosion behavior and surface properties of the coating produced by Active Screen plasma nitrating on Hot Work Tool Steel H11

Active Screen plasma nitriding is a new process that has recently developed surface engineering. Also while the elimination of the problems the conventional plasma nitriding، many developments in this field has provided. In this research، the effects of plasma nitriding parameters investigated on samples with different geometry. Samples were prepared were nitrided under the atmosphere content of 20%H2-80%N2، at the temperature of 520 Co، the duty cycles of 30%، 50% and 80% and with the frequencies of 10 kHz for 6 hours. Then the property of grooves surfaces and the behavior of corrosion investigate by experiments of the SEM، XRD، Roughness Micro Hardness measurement and test corrosion. The results of the experiments showed that the surface of the plasma nitriding samples are covered by Hexagonal form of the particles that the formation of this particles in plasma nitriding samples are due to sputtering of active screen and deposition on the surface during the process. With increasing thickness of the groove، frequency and duty cycle، roughness of surfaces raise. Also micro hardness rise with increasing the thickness of the groove and the duty cycle resulting from the increase in percent of deposition particle nitride. Hollow cathode phenomena occurred in sample with 2mm groove and 80% duty cycle in CPN. This will result in over heating of the sample which leads to a decrease hardness of the surface and an increasing in the Roughness of the surface. Also the results of the experiments XRD showed that، in the surface all of the samples form of γ : Fe4N and ε: Fe2-3N phases.