In this study, a combination of conventional plasma nitriding and cathodic cage plasma deposition (CCPD) at different temperatures (400 and 450 °C) is implemented to enhance the surface properties of AISI-M2 steel. This combination effectively improves the surface hardness and the formation of a favorable hardness gradient toward the core, which would benefit the load-bearing capacity of substrate. The duplex-treated samples exhibit iron nitrides $\left({\mathrm{Fe}}_4\mathrm{N},{ \mathrm{Fe}}_{2-3}\mathrm{N}\right)$ and titanium nitride $\left(\mathrm{TiN}\right)$ phases. The thickness of the hard-TiN layer is 1.35 and 2.37 μm, whereas the combined thickness of the hard film and diffusion layer is 87 and 124 μm, for treatment at 400 and 450 °C, respectively. The wear rate and friction coefficient are dramatically reduced by duplex treatment. The oxidative wear mechanism and adhesive wear mechanism are dominant for duplex-treated samples. This study suggests that the cathodic cage plasma deposition technique can attain a combination of hard film and diffusion layer. The plasma nitriding before CCPD is beneficial for attaining an adequate nitrogen diffusion layer thickness. The drawbacks of conventional TiN film deposition, such as “egg-shell” problems, can be removed.

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.

AISI D6 tool steel and AISI 304 stainless steel are among the most widely used material in the industry. However, this application field can still be expanded through the coatings deposition. In this regard, the objective of this work was to evaluate the impact of coatings application by cathodic cage technique using Hastelloy’s cathodic cage, on corrosion resistance of these steels. Two treatment temperatures were compared. The samples were characterized by Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-Ray Diffraction with the application of the Rietveld routine and corrosion test. The results showed the formation of multiphase layers that contributed to corrosion potentials reduction for treatments at 400 °C, being more effective when applied on AISI D6. It was observed that the corrosion resistance is influenced by the temperature, which was attributed to the precipitation of chromium nitride and iron oxide at 450 ºC.