# Optimizing Surface Properties of AISI 409 Stainless Steel through Duplex Treatment Consisting of Plasma Nitriding and Vanadium-Based Deposition

## TL;DR

This paper explores combining plasma nitriding and vanadium deposition to improve the durability and performance of stainless steel for automotive use.

## Contribution

The novelty lies in combining plasma nitriding and vanadium-based deposition to enhance mechanical and corrosion properties of AISI 409 stainless steel.

## Key findings

- Duplex treatment increased surface hardness by 5.7 times and wear resistance by 33.5 times.
- Vanadium deposition improved corrosion resistance, shifting electrochemical potential from −396 mV to −221 mV.
- The treatment is suitable for automotive exhaust systems requiring lightweight and durable materials.

## Abstract

This
study proposes a surface modification methodology
for AISI
409 stainless steel by combining cathodic cage plasma nitriding (CCPN)
and deposition (CCPD), evaluating the benefits of this duplex treatment
over individual treatments. The mechanical strength, tribological
behavior, and corrosion resistance of the treated surfaces were investigated
in relation to processing parameters and resulting microstructures.
Analyses were performed using XRD, SEM, Vickers microhardness, ball-on-disc
testing, and corrosion testing in a 3.5% NaCl solution. The duplex
treatment at 400 and 450 °C, consisting of CCPN followed by CCPD,
promoted significant surface modifications. Nitriding resulted in
a thick layer of Fe3N, Fe4N, and CrN, increasing
hardness and wear resistance, with final improvements of 5.7 and 33.5
times, respectively. The subsequent VN deposition enhanced corrosion
resistance, shifting the potential from −396 mV to −221
mV, indicating reduced electrochemical activity. These results confirm
the treatment’s potential for automotive exhaust systems, requiring
lightweight, durable materials in aggressive environments.