Improved wear resistance of AISI-1045 steel by hybrid treatment of plasma nitriding and post-oxidation

In this work, high-temperature plasma nitriding is used to improve the surface hardness and wear resistance of AISI-1045 steel. Subsequently, plasma nitrided samples are post-oxidized for 30 and 60 min to investigate its resultant effect. The treated samples are analyzed by X-ray diffraction, Raman spectroscopy, microhardness tester, scanning electron microscopy, elemental dispersive spectroscopy, and ball-on-disc wear tester. The nitrided sample contains a white layer (Fe4N, Fe2-3N), and its post-oxidation form hematite (Fe2O3) and magnetite (Fe3O4) phases. A significant improvement in hardness (similar to 1050 HV) is attained for nitrided samples, while post-oxidation causes a small decrease in hardness. The thickness of the nitrided layer is 8.2 mu m, and it is further increased to 9.3 and 13.2 mu m by post-oxidation due to further diffusion of nitrogen. The thickness of the oxide layer is 1.5 mu m and 2 mu m. The presence of a white layer causes abrasive wear of sample, whereas sample with post-oxidation shows outstanding wear resistance with adhesive wear mechanism. The friction coefficient of the nitrided sample is further reduced by plasma post-oxidation. This work suggests that detrimental effects of the white layer due to the removal of hard abrasive particles can be avoided by plasma post-oxidation.

Automated summary

In this study, high-temperature plasma nitriding was used to improve the surface hardness and wear resistance of AISI-1045 steel. Post-oxidation treatment was applied to the nitrided samples to investigate its effect. The results showed that the nitrided sample had a white layer, while post-oxidation transformed it into hematite and magnetite phases. The hardness of the nitrided samples significantly increased, although post-oxidation caused a slight decrease. The thickness of the nitrided layer and oxide layer increased with post-oxidation treatment. The nitrided sample exhibited abrasive wear, while the post-oxidized sample showed outstanding wear resistance with an adhesive wear mechanism.