# Effect of Conventional and Cathodic Cage Plasma Nitriding on the Mechanical and Corrosion Behavior of AISI 420 Martensitic Stainless Steel

## TL;DR

This study compares two plasma nitriding methods to improve the hardness and corrosion resistance of a type of stainless steel.

## Contribution

The study introduces cathodic cage plasma nitriding as an effective alternative to conventional methods for enhancing steel properties.

## Key findings

- Cathodic cage plasma nitriding at 450 °C achieved high hardness (1011 HV0.5) with good adhesion.
- Nitrided samples showed improved corrosion resistance in salt solutions compared to untreated steel.
- Optimal results were achieved at specific temperatures without altering the steel's base structure.

## 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 HV0.5 for PN at 500 °C. Notably, CCPN at 450 °C achieved similar
hardness (1011 HV0.5) 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.