Performance enhancement by plasma nitriding at low gas pressure for 304 austenitic stainless steel

Surface Modification of Austenitic Stainless Steel by Means of Low Pressure Glow-Discharge Treatments with Nitrogen

“…Baranowska [21] and Baranowska et al [27] reported a small nitrogen incorporation during cathodic sputtering, which can be explained taking into account the low pressure of the treatment (2-3 Pa), which causes a high sputtering rate. On the other hand, as previously recalled, it was reported that nitriding treatments performed in the range 80-160 Pa allow a significant nitrogen incorporation [3,13,14,17], suggesting that, in these conditions, nitrogen feeding is larger than sputtering.…”

“…As a consequence, ion and fast neutral energy increases, so that sputtering rate becomes considerable [26] and etching is deep. The high ion energy can also increase the number of active nitrogen atoms [13,14], which are able to diffuse into the substrate if the nitrogen feeding is not completely counteracted by sputtering. Baranowska [21] and Baranowska et al [27] reported a The untreated samples had passive corrosion behavior, with very low anodic current density values, which rapidly increased owing to the occurrence of localized corrosion phenomena when the potential was higher than about +407 mV (Ag/AgCl).…”

“…An increase of nitriding efficiency was observed decreasing the treatment pressure, and a significant nitrogen incorporation was obtained when the process was performed in the range 80-160 Pa [3,13,14,17]. Wang et al [13] and Lu et al [14] reported that, on AISI 304 samples, the modified layer thickness increased significantly as the treatment pressure was decreased from 400 to 100 Pa. A greater nitrogen incorporation in S phase, observed with X-ray diffraction analysis, was obtained decreasing the pressure of a 400 • C nitriding treatment from 500 to 130 Pa on both AISI 316L and AISI 202 samples [3]. Moreover, in an our previous study [17], it was shown that, using low pressures, nitride precipitation may occur also for treatment temperature and duration suitable to produce nitride-free modified layers.…”

“…The characteristics of the nitrided layers depend on different nitriding techniques [1,[7][8][9][10], treatment parameters [1,3,[11][12][13][14] and alloy composition [1,3,11,15,16]. Even if the main critical parameter, which influences microstructure and phase composition of the modified layers, is recognized to be the treatment temperature, also treatment pressure plays a very important role.…”

Low Temperature Plasma Nitriding of Austenitic Stainless Steels

“…Although detail information is not written in a few papers, relatively high-nitrogen surface content and formation of a nitrided layer with the thickness of 10-20 μm are common to those previous studies [31][32][33][34][35]. More precise analysis and discussion are needed to investigate the essential processes, governing the inner nitriding behavior at a lower temperature than 700 K. High-density RF-DC plasma systems [36][37][38][39][40] provides a new way to further analyze this low temperature plasma nitriding by experiments.…”