Duplex Steels. Part II: Carbides and Nitrides

Knyazeva, Marina; Pohl, M.

doi:10.1007/s13632-013-0088-2

Cited by 95 publications

(43 citation statements)

References 12 publications

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“…On the other hand, lean DSS have been found to be affected only by nitrides formation [7]. In any case, all DSS are sensitive to nitrides precipitation, as they contain significant percentages of nitrogen [7,11]. Nitrides formation is strictly related to the variation of temperature of the ferrite solubility against nitrogen, which increases at high temperature, thus bringing ferrite in supersaturated solid-solution conditions.…”

Section: Introductionmentioning

confidence: 99%

σ-Phase in Lean Duplex Stainless Steel Sheets

Breda

Pellizzari

Frigo³

2015

Acta Metall. Sin. (Engl. Lett.)

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The precipitation kinetics of secondary phases in two austeno-ferritic lean duplex stainless steels (lean DSS) were examined after aging the materials at 800°C. Owing to the instability of ferrite, all DSS are known to be sensitive to solid-state phase transformations in the critical temperature range 600-1,000°C and different secondary phases may form, depending on composition and microstructure. The performed thermodynamic simulations revealed the proneness to the precipitation of such phases also have been done in lean DSS, but only information on the equilibrium microstructures were achieved. Therefore, the materials were aged at various times, in order to verify the simulations and determine the precipitation kinetics. The occurred structural modifications were observed and quantified by scanning electron microscope and X-ray diffraction measurements, determining phase type, composition and volumetric fraction. At 800°C, grade 2101 was found to be only affected by Cr 2 N nitrides precipitation, whereas a significant amount of r-phase was found to form in LDX 2404 for treatment longer than 1 h, almost totally replacing ferrite after 50 h. Up to now, the intermetallic r-phase has been observed only in the high alloyed DSS, and the unexpected precipitation in grade 2404 highlighted that the increased content of molybdenum in this steel might be considered as determinant for the formation.

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Section: Introductionmentioning

confidence: 99%

σ-Phase in Lean Duplex Stainless Steel Sheets

Breda

Pellizzari

Frigo³

2015

Acta Metall. Sin. (Engl. Lett.)

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“…The scanning electron microscope through Energy-Dispersive X-ray Spectroscopy (SEM/EDS) can investigate the chemical features of the phases belonging to the material. In particular, the way in which alloying elements distributes inside ferrite rather than inside austenite and can be appreciated [20,21]. The most significant results of the chemical composition analysis are hence briefly reported in the following ( Table 3), considering that the concentration of each element is expressed as a percentage by weight.…”

Section: Resultsmentioning

confidence: 99%

Transformation-Induced Plasticity in Super Duplex Stainless Steel F55-UNS S32760

Ciuffini

Barella

Cecca

et al. 2019

Metals

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: Due to their unique combination of properties, Super Duplex Stainless Steels (SDSSs) are materials of choice in many industries. Their applications and markets are growing continuously, and without any doubt, there is a great potential for further volume increase. In recent years, intensive research has been performed on lean SDSSs improving mechanical properties exploiting the lack of nickel to generate metastable γ-austenite, resulting in transformation-induced plasticity (TRIP) effect. In the present work, a commercial F55-UNS S32760 SDSS have been studied coupling its microstructural features, especially secondary austenitic precipitates, and tensile properties, after different thermal treatments. First, the investigated specimens have been undergone to a thermal treatment solution, and then, to an annealing treatment with different holding times, in order to simulate the common hot-forming industrial practice. The results of microstructural investigations and mechanical testing highlight the occurrence of TRIP processes. This feature has been related to the Magee effect, concerning the secondary austenitic precipitates nucleated via martensitic-shear transformation.

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“…After aging 60 min at 850 • C (Figure 11c), DL-EPR reactivation occurred essentially at α/γ interfaces, but in this case the IGC attack appeared shallow despite the formation of large precipitates. The EDS line profile analysis performed across the precipitates grown at the α/γ interface in the sample aged at 750 • C for 60 min (Figure 11b) revealed peaks related to Cr, N, Mo, and C, confirming the formation of chromium nitrides but also chromium and perhaps molybdenum carbides (likely of the M 23 C 6 -type [36]). Moreover, in the sample aged for 60 min at 850 • C, SEM-EDS semi-quantitative analysis on a bright region at the α/γ interface (Spectrum 4 in Figure 11c) confirmed the formation of σ phase.…”

Section: Double Loop Electrochemical Potentiokinetic Reactivation (Dlmentioning

confidence: 94%

Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

Zanotto

Grassi

Balbo

et al. 2019

Metals

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This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times.

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Duplex Steels. Part II: Carbides and Nitrides

Cited by 95 publications

References 12 publications

σ-Phase in Lean Duplex Stainless Steel Sheets

σ-Phase in Lean Duplex Stainless Steel Sheets

Transformation-Induced Plasticity in Super Duplex Stainless Steel F55-UNS S32760

Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

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