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AISI 5160 steel has high toughness and ductility. However, in specific applications, better tribological performance is required. In this sense, the study's objective was to perform plasma nitriding with Hastelloy's cathodic cage followed by the conventional plasma nitriding in AISI 5160 steel to produce high hardness and wear resistance. The results showed that the samples and cutting tools subjected to this process showed higher wear resistance than untreated samples and high-speed steel tools. The sample submitted to treatments with 450°C and 3 h showed greater surface hardness and less volume loss in the mechanical and machining tests. Therefore, the duplex treatment presented in this work with posterior plasma nitriding proved efficient with the low processing time.

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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% H 2(g) and 20% N 2(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-Fe 3 N and γ ′-Fe 4 N 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.