K. Taherkhani - Department of Mining and Metallurgical Engineering,Amirkabir University of Technology, Tehran, Iran
F. Mahboubi

Nitriding is a surface treatment technique used to introduce nitrogen into metallic materials to improve their surface hardness, mechanical properties, wear resistance and corrosion resistance. This paper investigated the effect of plasma nitriding on samples with different grooves. Steel blocks prepared from DIN1.2344 hot working steel were plasma nitrided under the gas mixture %75H2-%25N2 at temperature of 500 c for 5h at different duty cycles and frequencies. Then compound and diffusion layer, profile micro hardness and phase structural property of surface of groove investigated by SEM and micro hardness measure. The results of the experiments showed that with increasing the thickness of the groove and duty cycle compound layer, diffusion layer and micro hardness rise due to the increase in percent of deposition particle nitride. Micro hardness and compound layer decreasing with increase frequency. Hollow cathode effect occurred in sample with small groove and high duty cycle in plasma nitriding. This will result in over heating of the sample which leads to a decrease hardness of surface to core and decrease the depth of nitrogen diffusion

Pulse Plasma Nitriding, Frequency, Duty Cycle, Hot work steel