Hollow Cathodic Plasma Source Nitriding Of Aisi 4140 Steel

AISI 4140 low alloy steel samples were treated using conventional plasma nitriding (CPN) and hollow cathodic plasma source nitriding (HCPSN) treatments. The results show the substantial impact of the electric potential of the nitriding process on the microstructure, topography, surface roughness and chemical characteristics of the CPN and HCPSN nitrided samples. The HCPSN sample presented the epsilon-Fe2-3N phase at a higher intensity than the CPN sample. XPS results showed that the modified surface of the HCPSN sample consisted of nitrides and oxides during the deposition. Electrochemical impedance spectroscopy and potentiodynamic polarization measurement revealed that the HCPSN sample had better corrosion resistance in neutral 3.5 wt-% NaCl solution. The results demonstrated that the mechanisms of the HCPSN process can be described by the 'sputtering-deposition-adsorption-diffusion' model.