Abstract
AISI 1020 steel was plasma nitrocarburized under different process parameters regarding time (1, 4 and 12 h), temperature (500, 570 and 640 °C) and different CO₂ ratio. The fatigue strength of plasma nitrocarburized AISI 1020 steel has been assessed by using a rotating bending fatigue machine and observed by scanning electron microscopy (SEM). In addition, the obtained results have been compared with the fatigue limits of plasma nitrided AISI 1020 steel. It has been found that plasma nitrocarburizing improves the fatigue strength with increased process times, but the fatigue strength decreases with growing CO₂ ratios. Fatigue strength and fatigue limit depend on treatment temperature. Their maximum was found at 570 °C.

Key words
plasma nitrocarburizing, fatigue strength

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