Quantification of sigma-phase evolution in thermally aged 2205 duplex stainless steel

Warren, Alexander; Harniman, Robert L.; Guo, Ziqi; Younes, C.M.; Flewitt, Peter E J; Scott, Thomas Bligh

doi:10.1007/s10853-015-9131-9

Cited by 45 publications

(23 citation statements)

References 34 publications

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“…Ferrite and austenite also did not show any specific texturing before aging, as shown in Figure 3. A similar observation was reported by Warren et al [35], who concluded that no specific σ nucleation orientation relationship relative to the parent δ was favored. However, it is not possible to conclude whether the apparently random orientation of σ was inherited from the parent δ or not.…”

Section: Discussionsupporting

confidence: 87%

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

et al. 2018

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Sigma phase is commonly considered to be the most deleterious secondary phase precipitating in duplex stainless steels, as it results in an extreme reduction of corrosion resistance and toughness. Previous studies have mainly focused on the kinetics of sigma phase precipitation and influences on properties and only a few works have studied the morphology of sigma phase and its influences on material properties. Therefore, the influence of sigma phase morphology on the degradation of corrosion resistance and mechanical properties of 2507 super duplex stainless steel (SDSS) was studied after 10 h of arc heat treatment using optical and scanning electron microscopy, electron backscattered diffraction analysis, corrosion testing, and thermodynamic calculations. A stationary arc was applied on the 2507 SDSS disc mounted on a water-cooled chamber, producing a steady-state temperature gradient covering the entire temperature range from room temperature to the melting point. Sigma phase was the major intermetallic precipitating between 630 °C and 1010 °C and its morphology changed from blocky to fine coral-shaped with decreasing aging temperature. At the same time, the average thickness of the precipitates decreased from 2.9 µm to 0.5 µm. The chemical composition of sigma was similar to that predicted by thermodynamic calculations when formed at 800–900 °C, but deviated at higher and lower temperatures. The formation of blocky sigma phase introduced local strain in the bulk of the primary austenite grains. However, the local strain was most pronounced in the secondary austenite grains next to the coral-shaped sigma phase precipitating at lower temperatures. Microstructures with blocky and coral-shaped sigma phase particles were prone to develop microscale cracks and local corrosion, respectively. Local corrosion occurred primarily in ferrite and in secondary austenite, which was predicted by thermodynamic calculations to have a low pitting resistance equivalent. To conclude, the influence of sigma phase morphology on the degradation of properties was summarized in two diagrams as functions of the level of static load and the severity of the corrosive environment.

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Section: Discussionsupporting

confidence: 87%

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

et al. 2018

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“…It has been proved that pitting occurring in chromium-depleted areas are associated with the precipitated phase [30,31]. When combined with Figures 2f and 7a, the ferrite was almost occupied by the σ phase and the secondary austenite, which often has relatively low Cr content than the σ or…”

Section: Discussionmentioning

confidence: 84%

Corrosion Behavior Difference in Initial Period for Hot-Rolled and Cold-Rolled 2205 Duplex Stainless Steels

Gao

Wang

Sun

et al. 2018

Metals

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Precipitate phases often play an important role on the corrosion resistance of 2205 Duplex stainless steels (DSS). In the present paper, the microstructure and the corrosion resistance of the hot-rolled and cold-rolled 2205 steels aged for different times at 850 • C was investigated through XRD, SEM, and potentiodynamic polarization. It was discovered that the Chi(χ) phase and Sigm(σ) phase were precipitated in turn following the aging treatment of the hot-rolled and cold-rolled steels, but the precipitate amount in the cold-rolled samples was significantly higher when compared to the hot-rolled samples. The corrosion resistance of the solution-annealed cold-rolled samples was similar to the hot-rolled samples, but the corrosion resistance of the cold-rolled sample with precipitate was weaker when compared to the hot-rolled sample following aging treatment. Pitting preferentially initiates in the Cr-depleted region from the σ phase in the aged hot-rolled 2205, becoming increasingly severe during aging for a long lime. Adversely, the initiation of pitting corrosion might occur at the phase boundary, defects, and martensite in the aged cold-rolled 2205. The σ phase was further selectively dissolved through the electrochemical method to investigate the difference in microstructure and corrosion behavior of the hot-rolled and cold-rolled 2205 duplex stainless steels.

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“…No sigma phase appears below 650˚C. The longer stayed at 850˚C, the more of the σ phase precipitation [5] [6].…”

Section: N Content σ Phase Control Cooling Rate Considerationmentioning

confidence: 99%

The Processability Improvement of Duplex Stainless Steel

Liu¹,

Benthem²

2016

OALib

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Quantification of sigma-phase evolution in thermally aged 2205 duplex stainless steel

Cited by 45 publications

References 34 publications

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

Corrosion Behavior Difference in Initial Period for Hot-Rolled and Cold-Rolled 2205 Duplex Stainless Steels

The Processability Improvement of Duplex Stainless Steel

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