Influence of the microstructure on the corrosion resistance of plasma-nitrided austenitic stainless steel 304L and 316L

Abstract

Austenitic stainless steels are widely used in medical and food industries because of their excellent corrosion resistance. However, they suffer from weak wear resistance due to their low hardness. To improve this, plasma nitriding processes have been successfully applied to austenitic stainless steels, thereby forming a thin and very hard diffusion layer, the so-called S-phase. In the present study, the austenitic stainless steels AISI 304L and AISI 316L with different microstructures and surface modifications were used to examine the influence of the steel microstructure on the plasma nitriding behavior and corrosion properties. In a first step, solution annealed steel plates were cold-rolled with 38% deformation degree. Then, the samples were prepared with three kinds of mechanical surface treatments. The specimens were plasma nitrided for 360 min in a H2N2 atmosphere at 420 °C. X-ray diffraction measurements confirmed the presence of the S-phase at the sample surface, austenite and body centered cubic (bcc)-iron. The specimens were comprehensively characterized by means of optical microscopy, scanning electron microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, surface roughness and nano-indentation measurements to provide the formulation of dependencies between microstructure and nitriding behavior. The corrosion behavior was examined by potentio-dynamic polarization measurements in 0.05 M and 0.5 M sulfuric acid and by salt spray testing

Corrosion behavior of 316L austenitic steel processed by selective laser melting, hot‐isostatic pressing, and casting

“…Grade 316L austenitic steel is normally used when a certain level of corrosion resistance is required, rather than to meet other conditions such as hardness or strength. Therefore, austenitic stainless steels are widely used in medical or food industries because of their excellent anti‐corrosion properties due to the presence of a thin protective oxide film which forms on the material's surface during operation . In recent years, steel manufacture using powder metallurgical processes, involving for example sintering or hot‐pressing, has become increasingly common .…”

Influence of material condition and chemical composition on the properties of plasma‐nitrided austenitic steels

“…Identische Befunde an den Werkstoffen 1.4307 und 1.4404 wurden in vorherigen Arbeiten festgestellt, bei der sich bei einem Umformgrad von 38 % bei 1.4307 mittels Röntgendiffraktometrie (XRD) ca. 10 % Umformmartensit gebildet hat, während bei 1.4404 kein Martensit detektierbar war [26]. Dies ist damit zu erklären, dass die Austenitphase in den Werkstoffen 1.4404 und 1.4571 aufgrund des höheren Quotienten aus Ni‐ und Cr‐Äquivalent stabilisierter vorliegt als bei den Werkstoffen 1.4307 und 1.4571, Tabelle 1.…”

“…Allerdings ist aufgrund der niedrigen Prozesstemperaturen davon auszugehen, dass sich bei 420 °C keine Nitridausscheidungen bilden und die Verbesserung der Korrosionsbeständigkeit auf die höhere Dicke der S‐Phase beim 420 °C‐Prozess zurückzuführen ist. Mittels Röntgenbeugung bei streifendem Einfall wurden bei den so behandelten Proben, unabhängig von Behandlungsparameter und Umformgrad (bis 40 %), keine Nitride oder Karbide nachgewiesen [26].…”

Effect of martensite transformation on chemical composition, semiconductor property and corrosion resistance of passive film on SAE 304 stainless steel

“…Stainless steel is a widely used metallic material due to excellent mechanical properties and corrosion resistance [1][2][3][4][5][6][7][8]. As a common processing method for stainless steel, cold working can result in the formation of residual stress and a strain-induced martensite due to plastic deformation, which can lead to the deterioration of the corrosion resistance through an increase in the number of surface active sites [9].…”