Abstract
AISI 420 martensitic stainless steel was treated via conventional plasma nitriding (PN) and cathodic cage plasma nitriding (CCPN) at temperatures ranging from 400 to 500 °C for 5 h to enhance surface properties. X-ray diffraction and scanning electron microscopy analyses confirmed uniform nitride layer formation, and microhardness measurements showed a peak hardness of 1270 HV(0).(5) for PN at 500 °C. Notably, CCPN at 450 °C achieved similar hardness (1011 HV(0).(5)) alongside excellent adhesion (HF1-HF2), highlighting the effectiveness of the cathodic cage technique. Electrochemical impedance spectroscopy and open-circuit potential tests in 3.5 wt % NaCl showed improved corrosion resistance in all nitrided samples compared to the untreated steel. These results indicate that specific nitriding conditions, particularly PN at 450 °C and CCPN at 400 °C, achieve an optimal balance of hardness, corrosion protection, and interfacial toughness while preserving the substrate's inherent microstructure.