Effect of different mo contents on tensile and corrosion behaviors of CD4MCU cast duplex stainless steels

Jang, Younghwan; Kim, Sangshik; Lee, Je-Hyun

doi:10.1007/s11661-005-0215-z

Cited by 15 publications

(4 citation statements)

References 10 publications

(10 reference statements)

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“…In duplex stainless steels, austenite has been believed to be a soft phase and the strength was enhanced by increasing the amount of ferrite. 34,35) However, nitrogen in DSS mainly dissolved in austenite due to its high solubility of about 0.45 wt% in the face-centered-cubic (fcc) lattice. 16) Indeed, the effect of the nitrogen content on the strength of austenite is quite important.…”

Section: Discussionmentioning

confidence: 99%

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

et al. 2010

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The DSS ingot was made by standard vacuum melting and casting, which possessed duplex ferritic-austenitic mi- 286© 2010 ISIJ ISIJ International, Vol. 50 (2010) In the present paper, the precipitation behavior of secondary phases in Lean Duplex Stainless Steel (LDX) 2101 had been studied. The alloy has a typical ferritic-austenitic duplex structure after solution treatment. Isothermal ageing treatments were carried out over the temperature range from 700 to 850°C for the period between 2 min and 1 440 min. Cr 2 N-type nitrides were formed as the main product of precipitates, together with small amount of Cr 23 C 6 -type carbides. Increase of N content and decrease of Cr and Mo contents in the steel had led to the absence of s-phase. Due to the solid solution strengthening by interstitial atoms, the hardness value of austenite was measured to be higher than that of ferrite. With increasing the isothermal ageing time, precipitates were observed to be preferentially nucleated at the d/g interface and grown toward the d phase. The d/g interfce migrated from the precipitate particles into d phase, leaving the precipitates behind along the original interfaces, which could increase the size of the secondary austenite (gЈ) phase and decrease the hardness of both austenite and ferrite. Inside gЈ phase, the hardness was measured to increase from about 3.20 GPa at the original interface to about 3.75 GPa at the newly formed interface of d/gЈ. The isothermal kinetics for the precipitation of secondary phases was measured to obey the JMAK-type law. The TTT (time-temperature-transformation) curve was constructed based on the measurements, which seems to have resulted from the overlap of two different precipitated products. The average impact energy at room temperature for the sample after solid solution treatment was measured to be 105 J. When 2 % secondary phases were precipitated during ageing, the impact energy decreased to about 43 J, reduced by about 59 % as compared with the as-annealed sample, indicating that formation of secondary phases can result in dramatic decrease of steel toughness.

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Section: Discussionmentioning

confidence: 99%

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

et al. 2010

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“…Manganese exists in passive films in the form of oxidation states II and IIII [61] . Jang reported that adding 0.8 wt.% manganese to CD4MCU cast duplex stainless steel negatively impacts the pitting corrosion resistance, but the pitting corrosion resistance recovers by adding 2 wt.% manganese [62] .…”

Section: Manganese Elementmentioning

confidence: 99%

A review on pitting corrosion and environmentally assisted cracking on duplex stainless steel

Liu¹,

Du²,

Wang³

et al. 2023

Microstructures

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Duplex stainless steel is widely used in the petrochemical, maritime, and food industries. However, duplex stainless steel has the problem of corrosion failures during use. This topic has not been comprehensively and academically reviewed. These factors motivate the authors to review the developments in the corrosion research of duplex stainless steel. The review found that the primary reasons for the failure of duplex stainless steels are pitting corrosion and chloride-induced stress corrosion cracking. After being submerged in water, the evolution of the passive film on the duplex stainless steel can be loosely classified into three stages: nucleation, rapid growth, and stable growth stages. Instead of dramatic rupture, the passive film rupture process is a continuous metal oxidation process. Environmental factors scarcely affect the double-layer structure of the passive film, but they affect the film's overall thickness, oxide ratio, and defect concentration. The six mechanisms of alloying elements on pitting corrosion are summarized as stabilization, ineffective, soluble precipitates, soluble inclusions, insoluble inclusions, and wrapping mechanisms. In environments containing chlorides, ferrite undergoes pitting corrosion more easily than austenite. However, the pitting corrosion resistance reverses when sufficiently large deformation is used. The mechanisms of pitting corrosion induced by precipitates include the Cr-depletion, microgalvanic, and high-stress field theories. Chloride-induced cracks always initiate in the corrosion pits and blunt when encountering austenite. Phase boundaries are both strong hydrogen traps and rapid hydrogen diffusion pathways during hydrogen-induced stress cracking.

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“…Therefore, DSS is replacing conventional austenitic or ferritic stainless steels in many industrial applications because of its combined advantages of better mechanical and corrosion properties. [1][2][3][4][5] DSS contains austenite stabilizing elements like Ni, Mn, C, N and Cu as well as ferrite stabilizing elements like Cr, Mo and Si. The recent skyrocketing raw material cost stimulates development of the DSSs with less alloying.…”

Section: Introductionmentioning

confidence: 99%

In-situ Observation of δ↔γ Phase Transformations in Duplex Stainless Steel Containing Different Nitrogen Contents

Zhao

Sun

et al. 2017

ISIJ International

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The characteristics of the γ ↔δ phase transformations were observed on the surface of duplex stainless steels with different nitrogen concentrations by the Ultra High Temperature Confocal Laser Scanning Microscope (UHT-CSLM). The effects of the nitrogen content on the phase transformations are discussed based on the experimental results and thermodynamic calculations. It is found that the migration of the δ/γ IB is the main form of the phase transformation and leads to the continuous decline and final disappearance of the retained γ-phase during the γ→δ phase transformation in the high nitrogen steel (N1) and low nitrogen steel (N2). During the δ→γ phase transformation, the γ -cells prefer to precipitate along the δ/δ GBs and develop into the δ -ferrite matrix with finger-like or sword-like patterns. Then the γ-cells also nucleate in the δ -grains with a sword-like pattern and the growing speed in the longitudinal direction is much faster than that in the lateral direction. More importantly, the high nitrogen content can hinder the migration of δ/γ IBs during the γ→δ transformation and also promote the nucleation and growth of γ -phase during the δ→γ transformation by increasing both the starting and finishing temperatures of the phase transformation. Interestingly, the original δ/δ GB which is covered by the precipitation of γ -phase during the δ→γ transformation will reappear first at the same position by the moving of δ/γ IBs during the γ→δ transformation, but it is unstable and migrates fast with further heating.

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Effect of different mo contents on tensile and corrosion behaviors of CD4MCU cast duplex stainless steels

Cited by 15 publications

References 10 publications

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

Precipitation of Secondary Phases in Lean Duplex Stainless Steel 2101 during Isothermal Ageing

A review on pitting corrosion and environmentally assisted cracking on duplex stainless steel

<i>In-situ</i> Observation of <i>δ</i>↔<i>γ</i> Phase Transformations in Duplex Stainless Steel Containing Different Nitrogen Contents

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