The effect of σ-phase precipitation at 800°C on the mechanical properties of a high alloyed duplex stainless steel

Wilms, Marc; Gadgil, V.J.; Krougman, J.M.; Kolster, B.H.

doi:10.1080/09603409.1991.11689654

Cited by 46 publications

(18 citation statements)

References 3 publications

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“…First of all, it can be observed that the initial values of nanohardness related to both phases in S1 are very similar with an average of 6.2 GPa. These specific values of nanohardness are higher than other values presented in previous works from 3.2 GPa to 4.4 GPa [26,27]. The main reason to justify this observation is based on work-hardening experimental result related to this sigma phase is lower than reported by Guimaraes et al [46], who measured values of 522 HV in an AISI 446 stainless steel.…”

Section: Nanoindentation Hardness Measurements In Austenite and Ferricontrasting

confidence: 53%

“…One of the most known and representative detrimental phases is the precipitation of the sigma phase (σ), a Cr-and Mo-rich intermetallic compound [12][13][14][15][16][17][18][19][20][21]. This σ phase shows a tetragonal crystallographic structure with 32 atoms per unit cell [22] making possible a considerable increase in the resultant hardness, whereas a decrease in the toughness as well as elongation is also observed [23][24][25][26][27]. In addition, a change in the fracture type from transgranular to intergranular is obtained as a function of higher amounts of σ phase [28].…”

Section: Introductionmentioning

confidence: 99%

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Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Argandoña¹,

Palacio

Berlanga

et al. 2017

Metals

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Abstract:The aim of this work is to study the hardness of the ferrite, austenite and sigma phases of a UNS S32760 superduplex stainless steel submitted to different thermal treatments, thus leading to different percentages of the mentioned phases. A comparative study has been performed in order to evaluate the resulting mechanical properties of these phases by using hardness, microhardness and nanoindentation techniques. In addition, optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been also used to identify their presence and distribution. Finally, the experimental results have shown that the resulting hardness values were increased as a function of a longer heat treatment duration which it is associated to the formation of a higher percentage of the sigma phase. However, nanoindentation hardness measurements of this sigma phase showed lower values than expected, being a combination of two main factors, namely the complexity of the sigma phase structure as well as the surface finish (roughness).

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Section: Nanoindentation Hardness Measurements In Austenite and Ferricontrasting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Argandoña¹,

Palacio

Berlanga

et al. 2017

Metals

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“…The rate of formation and growth of σ-phase increases as temperature is held at 800°C (1472°F) [31,32] and had deleterious effect on the alloy's mechanical properties. On the other hand, [33,34] reported that σ-phase will dissolve if held at 1000°C reverting into matrix, hence will not affect mechanical properties. This investigation has correlated formation and presence of σ-phase in heat resistant cast material HK-40 to its morphology and mechanical properties both at low and high temperature.…”

Section: Introductionmentioning

confidence: 99%

Sigma Phase Formation and Embrittlement of Cast Iron-Chromium-Nickel (Fe-Cr-Ni) Alloys

Babakr¹,

Al‐Ahmari²,

Al-Jumayiah³

et al. 2008

JMMCE

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HK alloy is a member of the heat resistant cast alloy family (H-Series) steels. They are widely used in the petrochemical industry for components requiring enhanced high temperature properties. Microstructural changes occurring at high temperature clearly affects its mechanical properties. These properties have been shown in HK-40 steel subjected to high-temperature degradation and prone to the formation of sigma phase. The investigation carried out included metallurgical analysis, materials characterization and mechanical analysis. Metallurgical analysis included advanced metallography techniques to characterize its microstructure morphology and properties. Significant depletion of vital precipitates observed that definitely degraded its high temperature properties. Mechanical analysis included hardness profile, tensile testing of samples taken from the tree supports and tested in room temperature and in 800°C environments. Experimental results revealed that the structure of HK-40 affected by the formation of the high temperature brittle sigma-σ-phase. Nonetheless, mechanical properties did not suffer much at higher temperature.

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“…The effect of undesired secondary phases like sigma, chi, and intermetallic precipitates principally chromium rich phases like carbides and nitrides has been widely studied [1][2][3][4][5] . Sigma phase is by far the most important secondary phase because its relatively large volume fraction produces a loss of toughness, ductility and corrosion resistance attending negotiation research spans in many disciplines [6][7][8][9][10][11] . Sigma phase is a hard, brittle phase, which is generally formed between 600 and 950 °C, with rapid kinetic formation; its nucleation is preferentially at the ferrite-austenite interfaces and presents different morphologies depending on thermal treatments 12,13 .…”

Section: Introductionmentioning

confidence: 99%

Relationship between microstructure and fracture types in a UNS S32205 duplex stainless steel

Biezma

Berlanga

Argandoña³

2013

Mat. Res.

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Duplex stainless steels are susceptible to the formation of sigma phase at high temperature which could potentially be responsible for catastrophic service failure of components. Thermal treatments were applied to duplex stainless steels in order to promote the precipitation of different fractions of sigma phase into a ferrite-austenite microstructure. Quantitative image analysis was employed to characterize the microstructure and Charpy impact tests were used in order to evaluate the mechanical degradation caused by sigma phase presence. The fracture morphology of the Charpy test specimens were thoroughly observed in SEM, looking for a correlation between the microstructure and the fracture types in UNS S32205 duplex stainless steel. The main conclusion is the strong embrittlement effect of sigma phase since it is possible to observe a transition from transgranular fracture to intergranular fracture as increases the percentage of sigma phase. Thus, the mixed modes of fracture are predominant in the present study with high dependence on sigma phase percentages obtained by different thermal treatments.

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The effect of σ-phase precipitation at 800°C on the mechanical properties of a high alloyed duplex stainless steel

Cited by 46 publications

References 3 publications

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Effect of the Temperature in the Mechanical Properties of Austenite, Ferrite and Sigma Phases of Duplex Stainless Steels Using Hardness, Microhardness and Nanoindentation Techniques

Sigma Phase Formation and Embrittlement of Cast Iron-Chromium-Nickel (Fe-Cr-Ni) Alloys

Relationship between microstructure and fracture types in a UNS S32205 duplex stainless steel

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