“…The peaks of γ N (111) and γ N (200) were widened and diffused resulting from the concentration gradient of nitrogen in the nitrided layer. The results of SEM and XRD indicated that the γ N phase was uniformly formed on both austenitic and ferritic phases revealing a possible transformation of ferrite into austenite phase because of the nitrogen as an alloying element stabilizes the austenite phase [18,19].…”
Section: Resultsmentioning
confidence: 99%
“…The peaks of γ N (111) and γ N (200) were widened and diffused resulting from the concentration gradient of nitrogen in the nitrided layer. The results of SEM and XRD indicated that the γ N phase was uniformly formed on both austenitic and ferritic phases revealing a possible transformation of ferrite into austenite phase because of the nitrogen as an alloying element stabilizes the austenite phase [18,19]. Figure 2 SEM surface morphology (a) and chemical composition (b) of nitrided 2205 DSS. Figure 3 Cross-section SEM image of nitrided 2205DSS. Figure 4 X-ray diffraction patterns of 2205 DSS samples (a) as-received and (b) nitrided.…”
A nitrogen expanded austenite (γ N ) layer with a thickness of 3 μm was prepared by plasma nitriding of 2205 duplex stainless steel (DSS) at 460°C for 1 h with hollow cathode discharge assistance. The microstructure and phase composition of nitrided specimens were examined. The electrical conductivity of nitrided samples was measured before and after the corrosion test, respectively. The corrosion current density of nitrided 2205 DSS polarized for 4 h was 1.3 μA cm −2 (at 0.6 V) and −1.4 μA cm −2 (at −0.1 V), respectively. The interfacial contact resistance (ICR) of the nitrided 2205 was 14.7 mΩ cm 2 which was much lower than that of bare 2205 DSS substrate (93.6 mΩ cm 2 ) after 4 h potentiostatic polarization at cathodic conditions. The corrosion resistance and electrical conductivity were evidently improved compared with 2205 DSS substrate.
“…The peaks of γ N (111) and γ N (200) were widened and diffused resulting from the concentration gradient of nitrogen in the nitrided layer. The results of SEM and XRD indicated that the γ N phase was uniformly formed on both austenitic and ferritic phases revealing a possible transformation of ferrite into austenite phase because of the nitrogen as an alloying element stabilizes the austenite phase [18,19].…”
Section: Resultsmentioning
confidence: 99%
“…The peaks of γ N (111) and γ N (200) were widened and diffused resulting from the concentration gradient of nitrogen in the nitrided layer. The results of SEM and XRD indicated that the γ N phase was uniformly formed on both austenitic and ferritic phases revealing a possible transformation of ferrite into austenite phase because of the nitrogen as an alloying element stabilizes the austenite phase [18,19]. Figure 2 SEM surface morphology (a) and chemical composition (b) of nitrided 2205 DSS. Figure 3 Cross-section SEM image of nitrided 2205DSS. Figure 4 X-ray diffraction patterns of 2205 DSS samples (a) as-received and (b) nitrided.…”
A nitrogen expanded austenite (γ N ) layer with a thickness of 3 μm was prepared by plasma nitriding of 2205 duplex stainless steel (DSS) at 460°C for 1 h with hollow cathode discharge assistance. The microstructure and phase composition of nitrided specimens were examined. The electrical conductivity of nitrided samples was measured before and after the corrosion test, respectively. The corrosion current density of nitrided 2205 DSS polarized for 4 h was 1.3 μA cm −2 (at 0.6 V) and −1.4 μA cm −2 (at −0.1 V), respectively. The interfacial contact resistance (ICR) of the nitrided 2205 was 14.7 mΩ cm 2 which was much lower than that of bare 2205 DSS substrate (93.6 mΩ cm 2 ) after 4 h potentiostatic polarization at cathodic conditions. The corrosion resistance and electrical conductivity were evidently improved compared with 2205 DSS substrate.
“…Recently, Dalton et al [140] performed a high-resolution spatially-resolved compositional and structural analysis of the δ-ferrite grains of 2205 duplex stainless steel samples nitrided in the range of 325-400 • C, and observed two competitive responses to nitriding. Some regions had a N content up to ~25 at.% and maintained a b.c.c.…”
Section: Characteristics Of the Modified Surface Layersmentioning
Low-temperature treatments have become a valuable method for improving the surface hardness of stainless steels, and thus their tribological properties, without impairing their corrosion resistance. By using treatment temperatures lower than those usually employed for nitriding or carburizing of low alloy steels or tool steels, it is possible to obtain a fairly fast (interstitial) diffusion of nitrogen and/or carbon atoms; on the contrary, the diffusion of substitutional atoms, as chromium atoms, has significantly slowed down, therefore the formation of chromium compounds is hindered, and corrosion resistance can be maintained. As a consequence, nitrogen and carbon atoms can be retained in solid solutions in an iron lattice well beyond their maximum solubility, and supersaturated solid solutions are produced. Depending on the iron lattice structure present in the stainless steel, the so-called “expanded austenite” or “S-phase”, “expanded ferrite”, and “expanded martensite” have been reported to be formed. This review summarizes the main studies on the characteristics and properties of these “expanded” phases and of the modified surface layers in which these phases form by using low-temperature treatments. A particular focus is on expanded martensite and expanded ferrite. Expanded austenite–S-phase is also discussed, with particular reference to the most recent studies.
“…Nitriding is the process of modifying a surface by which nitrogen is combined with other alloying elements, such as iron. It has been used to alter the surface 2205 DSS at low temperatures to improve the material's wear resistance, surface hardness, fatigue life and stability in a chlorine-rich environment [28]. Chemical etching is the process by which a material's surface is oxidized by chemical or electrochemical, for example, hot nitric acid, in order to enrich and enhance the surface functionality and surface area, respectively.…”
2205 duplex stainless steel suffers poor hot workability, especially whe1981hot-deformed. This investigation aims to determine the strain rate’s effect on the material’s dynamic recrystallization after heat treatment. Secondly, to ascertain the critical strain at which the recrystallization occurs. The as-rolled material was subjected to heat treatment at 1340 °C for some time. After heat treatment, the yielded equiaxed austenite morphology was used for this investigation. Gleeble 1500™ thermo-mechanical was used as a simulant in uniaxial compression mode. The deformation temperature was set at 850 °C, with maximum strain at 0.8 and carried out at 0.001 s-1, 0.01 s-1, 0.1 s-1, 1 s-1, 5 s-1 strain rates. The microstructure of before and after heat-treatment was evaluated using a light microscope, while the critical factors (stress and strain) were determined through the stress-strain curve. It was observed that the lowest strain rate generated the maximum critical stress and critical strain at 191.99 MPa and 0.08283, respectively. However, at the highest strain rate, the maximum critical stress and critical strain experienced by the material were at 336.32 MPa and 0.17577. Overall, it was established that the applied stain rate influenced the critical strain and stress of the material. It can be concluded that dynamic recrystallization can occur at any strain rate, but the applied stress determines the extent of the phenomenon.
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