Investigation nitride coating surface properties and wear on the hot work tool steel AISI H11 in the method pulsed plasma nitriding

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 c, the duty cycles of 30%, 50%, 80% and with frequencies of 10 kHz for 6 hours. Then the property of grooves surfaces investigate by experiments of the SEM, Roughness and Micro Hardness measurement. The results of the experiments showed that the surface of the plasma nitriding samples are covered by cauliflower form of particles that formation of this particles in plasma nitriding samples are due to sputtering of 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 duty cycle resulting from the increase in percent of deposition particle nitride. The 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. Then after the process plasma nitriding, the results of the pin on disk wear test showed that the nitrides coating have wear resistance better than the reference sample before treatment plasma nitriding.