Nitriding Process Characterization of Cold Worked AISI 304 and 316 Austenitic Stainless Steels

Abstract

The nitriding behavior of austenitic stainless steels (AISI 304 and 316) was studied by different cold work degree (0% (after heat treated), 10%, 20%, 30%, and 40%) before nitride processing. The microstructure, layer thickness, hardness, and chemical microcomposition were evaluated employing optical microscopy, Vickers hardness, and scanning electron microscopy techniques (WDS microanalysis). The initial cold work (previous plastic deformations) in both AISI 304 and 306 austenitic stainless steels does not show special influence in all applied nitriding kinetics (in layer thicknesses). The nitriding processes have formed two layers, one external layer formed by expanded austenite with high nitrogen content, followed by another thinner layer just below formed by expanded austenite with a high presence of carbon (back diffusion). An enhanced diffusion can be observed on AISI 304 steel comparing with AISI 316 steel (a nitrided layer thicker can be noticed in the AISI 304 steel). The mechanical strength of both steels after nitriding processes reveals significant hardness values, almost 1100 HV, on the nitrided layers.

Mapping the Accouterment Effects of Plasma Nitriding on AISI 316L in Biomedical Applications

“…Open circuit potential measurement provides efficient information about surface electrochemistry conditions in different simulated body fluids. Using the Ivium potentiostat multi-channel device, electrochemical experiments were conducted in various simulated body fluids to compare the corrosion behaviour of the plasma nitride and untreated samples [25][26][27][28][29][30]. The procedure was carried out utilizing a three-electrode setup, with the working electrode being the samples (both as-received and plasma nitrided), the counter electrode being platinum (Pt), and the reference electrode being Ag/AgCl (stored in KCl solution).…”