Surface characterization of active screen plasma nitrided low alloy steel (DIN 1.6580)

This paper considers the effects of plasma nitriding parameters including screen hole size, top lid type (screen or iron plate), temperature and composition of the treatment gas, on the surface properties of DIN 1.6580 low-alloy steel. Nitriding was carried out at 520, 550 and 580°C for 5 hr in the gas mixture of (N2/H2); 3:1 and 1:3. The properties of nitrided specimens were assessed using metallographic techniques, XRD, Micro-hardness measurements, and SEM. X-ray diffraction analysis confirmed the formation of and during the nitriding process. The findings show that the thickness of the compound layer increases with the increase in the treatment temperature and nitrogen percentage in the gas mixture moreover increase in the screen hole size has no effect on the compound layer thickness in the screen top lid condition but that an increase in the screen hole size at the same temperature results in an increase in the thickness of the compound layer in the iron plate top lid condition. The results of micro-hardness measurements indicate that surface hardness increases with the increase in the temperature and nitrogen volume in the treatment gas. It was also found that hardness values obtained using screen top lid are relatively greater than those obtained using iron plate top lid.