Effect of oxidation process on wear o 17CrNiMo6 steel after plasma nitriding

In this study, the effects of plasma nitriding and subsequent plasma oxidation processes on the tribological and microstructural properties of 17CrNiMo6 steel were investigated. Plasma nitriding was performed at 480 °C for 20 hours in a gas mixture of 25% H2-75% N2, followed by plasma oxidation at 500 °C for 0,5, 1 and 1,5 hours in gas mixtures of 25% O2-75% H2 and 50% O2-50% H2. Surface characterization was conducted using XRD, SEM, EDS and ball-on-disk wear tests. Microstructural examinations revealed the dominant formation of the Fe3N phase after plasma nitriding, while plasma oxidation led to the appearance of Fe2O3 and Fe3O4 phases. It was observed that short oxidation times produced compact and homogeneous oxide layers, whereas prolonged oxidation caused deterioration of layer integrity. Tribological tests indicated that the untreated specimen exhibited the highest wear values, while the specimens oxidized for 1 hour under 25% O2 and 50% O2 conditions achieved the lowest wear rates and optimum surface performance. Hardness measurements showed the highest value in the 25% O2 0,5h specimen, whereas prolonged oxidation resulted in a significant decrease in hardness. The obtained results demonstrate that controlled plasma oxidation processes following plasma nitriding can significantly improve the surface performance of 17CrNiMo6 steel. Keywords: Plasma nitriding, Plasma oxidation, Wear, 17CrNiMo6.