Influence of Nitriding Surface Treatment on Corrosion Characteristics of Ni-free SUS445 Stainless Steel

Abstract

The heat treatments of Ni-free SUS445 stainless steel under nitrogen and argon gas atmospheres were conducted at 1373–1473 K in the present study. The heat-treated samples were characterized by an X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GD-OES), and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The corrosion behavior of the heat-treated samples was evaluated by linear sweep voltammetry (LSV) measurements in a 0.5 mol dm⁻³ H₂SO₄ solution. The results revealed that the nitrided stainless steel at 1373 K presents the best corrosion resistance and the AlN, expanded austenite γ_N, CrN and Cr₂N phases appeared based on the XRD results. In contrast, the corrosion resistance of the heat-treated stainless steel under an argon atmosphere was decreased and there was no change in the microstructure.