بهسازي خواص سطحي فولاد كم آلياژ DIN 1.6580 با نيتروژن دهي پلاسمايي به روش توري (شبكه) فعال

SURFACE MODIFICATION OF A LOW ALLOY STEEL DIN 1.6580 WITH ACTIVE SCREEN PLASMA NITRIDING

This paper considers the effects of plasma nitriding parameters including screen hole size, top lid type (screen or iron plate), and the temperature as well as the composition of the treatment gas on surface properties of DIN 1.6580 low-alloy steel. Nitriding was carried out at 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 yʹ - Fe4N and s - Fe2_3N phases during the nitriding process. The findings show that the thickness of the compound layer increases with treatment temperature as well as nitrogen percentage in gas mixture and that an increase in screen hole size has no effect on the compound layer thickness under screen top lid condition and also that an increase in screen hole size at the same temperature results in an increase in the thickness of the compound layer under iron plate top lid condition. The results of micro-hardness measurements indicate that surface hardness increases with temperature as well as nitrogen volume in 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.