Measuring secondary phases in duplex stainless steels

: The properties of duplex stainless steels (DSSs) depend on the ferrite–austenite ratio and on the contents of secondary phases. Therefore, it is necessary to control the volume fractions, morphologies, and distribution patterns of all phases. The phases in the samples were identified using thermodynamic modeling and scanning electron microscopy. Investigated specimens were obtained after different heat treatments, such as solution annealing and quenching from 1050 to 1250 °C to obtain different amounts of ferrite and annealing at 850 °C to precipitate the σ-phase. Therefore, a metallographic technique for assessing the phases in DSSs based on selective etching and subsequent analysis according to ASTM E 1245 was developed. It was shown that the developed method of quantitative analysis based on selective etching and metallographic assessment according to ASTM E 1245 allows obtaining much more accurate results compared to the proposed ASTM E 562 method, which correlates well with the XRD quantitative phase analysis.

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The Analysis and Research of Secondary Phases Generated during Isothermal Aging of Duplex Stainless Steels

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.193-194.411 ◽

2012 ◽

Vol 193-194 ◽

pp. 411-417 ◽

Cited By ~ 1

Author(s):

Kai Lin ◽

Hong Qi Shi ◽

Li Qun Ma ◽

Yi Ding

Keyword(s):

Stainless Steels ◽

Isothermal Aging ◽

Heat Treating ◽

Duplex Stainless Steels ◽

Secondary Phases ◽

Factors Affecting ◽

Σ Phase ◽

Α Phase ◽

The Right ◽

Χ Phase

The properties and precipitation rules of secondary phases generated during isothermal aging of duplex stainless steels and factors affecting the precipitates were reviewed in this article. These secondary phases include carbides(M23C6,M7C3), nitrides(Cr2N,CrN) and intermetallic phases(σ-phase, χ-phase, Fe3Cr3Mo2Si2, R-phase, π-phase, α′-phase). With the right understanding about the phases, the aim is the suitable heat-treating processes would be chose to avoid the unfavorable influences of secondary phases.

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Effect of Secondary Phases Precipitation on Corrosion Resistance of Duplex Stainless Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.1495 ◽

2016 ◽

Vol 879 ◽

pp. 1495-1500 ◽

Cited By ~ 2

Author(s):

Luca Pezzato ◽

Mattia Lago ◽

Katya Brunelli ◽

Marco Breda ◽

Enrico Piva ◽

...

Keyword(s):

Corrosion Resistance ◽

Stainless Steels ◽

Room Temperature ◽

Volume Fraction ◽

Secondary Phase ◽

Duplex Stainless Steels ◽

Secondary Phases ◽

Critical Range ◽

Pitting Corrosion Resistance ◽

Equivalent Number

Duplex Stainless steels (DSS) are biphasic austeno-ferritic steels in which the best combination of mechanical and corrosion resistance properties is achieved for almost equal volume fraction of the phases. These steels are classified according to their pitting corrosion resistance, assessed by the PREN index (Pitting Resistance Equivalent Number) which, although qualitatively, is widely employed as comparison. The present work is aimed to study the pitting resistance of four DSS grades (SAF 2101, 2304, 2205 and 2507) in the as-received condition and after isothermal aging in the critical range 750°C-900°C, to highlight the effect of secondary phases precipitation on the corrosion behavior. The materials were potentiodynamically tested in artificial seawater (pH7) at room temperature and the corresponding Critical Pitting Temperatures (CPT) were determined according to ASTM G150. Secondary phase precipitation mainly affected the lean duplex grades whereas the high-alloyed DSS were more stable even if large precipitation occurred.

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Effect of secondary phases on 475 °C embrittlement of 1.4462 and 1.4501 duplex stainless steels at short-term heat treatment conditions

Materials Research Express ◽

10.1088/2053-1591/ab4b38 ◽

2019 ◽

Vol 6 (11) ◽

pp. 116595 ◽

Cited By ~ 2

Author(s):

Alptekin Kisasoz ◽

Gokhan Ozer ◽

Ahmet Karaaslan

Keyword(s):

Heat Treatment ◽

Stainless Steels ◽

Duplex Stainless Steels ◽

Secondary Phases ◽

Short Term ◽

Treatment Conditions

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Quantitative Description of Duplex Stainless Steels Microstructure Using Selective Etching

Metals ◽

10.3390/met11111750 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1750

Author(s):

Aleksandr Sergeevich Fedorov ◽

Andrey Igorevich Zhitenev ◽

Darya Andreevna Strekalovskaya ◽

Aleksandr Aleksandrovich Kur ◽

Alexey Aleksandrovich Alkhimenko

Keyword(s):

Stainless Steels ◽

Volume Fraction ◽

Quantitative Description ◽

Integrated Approach ◽

Selective Etching ◽

Duplex Stainless Steels ◽

Parameters Estimation ◽

Metallographic Analysis ◽

Secondary Phases ◽

Metallic Inclusions

The properties of duplex stainless steels (DSSs) depend on the ferrite–austenite ratio, on the content of secondary phases and on the contamination with non-metallic inclusions. To assess the quality of DSSs, it is necessary to use an integrated approach which includes controlling for the volume fraction, the morphology and the distribution of all phases and non-metallic inclusions. Samples of several grades of DSSs were obtained using various heat treatments, such as solution annealing and quenching from 1050 to 1250 °C to obtain different amounts of ferrite and to provoke annealing at 850 °C to precipitate σ-phase. As a result, a metallographic technique of phase analysis in DSSs based on selective etching and subsequent structure parameters estimation according to ASTM E1245 was developed. We demonstrated that the developed method of quantitative analysis based on selective etching and metallographic analysis according to ASTM E1245 allows us to obtaining much more accurate results, compared to the point count method described in ASTM E562 and to the XRD method.

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Stress Corrosion Cracking of Duplex Stainless Steels

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.794.552 ◽

2013 ◽

Vol 794 ◽

pp. 552-563 ◽

Cited By ~ 1

Author(s):

Indranil Chattoraj

Keyword(s):

Corrosion Resistance ◽

Stress Corrosion ◽

Stress Corrosion Cracking ◽

Stainless Steels ◽

Fracture Morphology ◽

Selective Dissolution ◽

Corrosion Cracking ◽

Duplex Stainless Steels ◽

Secondary Phases

The relative superiority of duplex stainless steels (DSS) over austenitic grades with regards to stress corrosion cracking (SCC) is discussed. The benefits of N to SCC resistance of DSS are provided. The selective dissolution of phases and its impact on corrosion SCC is reviewed. The hydrogen embrittlement of DSS is reviewed with emphasis on the ferrite participation, the role of environments and fracture morphology. The evolution of secondary phases and precipitates and the resultant change in corrosion resistance and SCC in DSS is discussed.

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Impact Toughness of Isothermally Treated Duplex Stainless Steels

MRS Proceedings ◽

10.1557/opl.2014.237 ◽

2014 ◽

Vol 1616 ◽

Author(s):

I. Calliari ◽

M. Breda ◽

G. Straffelini ◽

A. F. Miranda Perez ◽

F. A. Reyes Valdes

Keyword(s):

Impact Toughness ◽

Stainless Steels ◽

Intermetallic Phases ◽

Duplex Stainless Steels ◽

Secondary Phases ◽

Negative Effect ◽

Isothermal Heat Treatments ◽

Saf 2205 ◽

The Impact ◽

Duplex Steels

ABSTRACTDuplex stainless steels (DSS) have good mechanical and corrosion resistance properties which allow their application in very aggressive environments. However, their aging at 600–1000 °C causes the precipitation of dangerous intermetallic phases, resulting in serious detrimental effects on their interesting properties. These secondary phases are structural discontinuities which act as preferential cracks initiation sites and their negative effect is especially highlighted on toughness. For these reasons, many standards related to the manufacturing of DSS require the microstructure of these steels "free from intermetallics". In this paper, the effect of isothermal heat treatments on the impact toughness in two Duplex steels (SAF 2205 and Zeron®100) has been investigated, in order to study the influence of different amount of secondary phases on the toughness response.

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