Effect of plasma nitriding time on the structural and mechanical properties of AISI-O1 steel

Abstract

In this paper, the effect of plasma nitriding time on the improvement of surface microhardness of AISI O1 steel as a strategy to increase its wear resistance was addressed. The plasma nitriding was carried out in a controlled atmosphere (80% H2(g) and 20% N2(g)), temperature (500°C), and pressure (6 mbar), during the different amount of time (4, 5, and 6 hours). The material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and microhardness measurements. Moreover, microhardness measurements were carried out to investigate the mechanical properties. From the results, it was verified that the XRD patterns, SEM images, and EDS spectra confirmed the formation of a layer with ε-Fe3N and γ′-Fe4N phases in all nitrided samples. The sample AISI-O1 steel, which was nitrided for 6 hours, exhibited a hardness about 46% higher than the one measured for the untreated sample. This sample also showed the thicker layer, with a mean of 7.22 μm. Therefore, this thermochemical treatment can improve mechanical properties in AISI O1 steel, and suggest its use in compression tools to improve this tools life.