Phase instabilities during high temperature exposure of 316 austenitic stainless steel

Weiß, B.; Stickler, R.

doi:10.1007/bf02647659

Cited by 731 publications

(296 citation statements)

References 14 publications

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“…For cast stainless steels, the main microstructural mechanisms of thermal aging at <500°C are associated with the precipitation of additional phases in the ferrite: (a) formation of a Cr-rich a¢-phase through Spinodal decomposition, (b) precipitation of a G-phase (Ni, Si-rich) and M 23 C 6 carbide, and (c) additional precipitation and/ or growth of existing carbides and nitrides at the ferrite/austenite phase boundaries. [2][3][4][5][6][7][8][9]13,17,19,[29][30][31][32][33][34][35][36] In the austenite matrix phase, thermal aging induces various precipitations but usually causes a negligible to moderate effect on the mechanical properties of the phase. [3][4][5][6][7] The effect on toughness, in particular, is less pronounced in the austenitic phase.…”

Section: Mechanism Of Thermal Embrittlement and Influential Factorsmentioning

confidence: 99%

“…[2][3][4][5][6][7]29 The primary embrittlement mechanism, the Spinodal decomposition of ferrite, should have higher activation energy because of the short range and fast characteristics of the process. 3,7,17,19,31,32,35 The strengthening in ferrite is caused primarily by Spinodal decomposition of ferrite to form the Cr-rich a¢-phase, and consequently the kinetics of thermal embrittlement should be primarily controlled by the size and spacing of the a¢-phase.…”

Section: Mechanism Of Thermal Embrittlement and Influential Factorsmentioning

confidence: 99%

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Thermal Aging Phenomena in Cast Duplex Stainless Steels

Byun

Yang

Overman

et al. 2015

JOM

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Cast stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. The thermal embrittlement of CASS components is one of the most serious concerns related to the extended-term operation of nuclear power plants. Many past researches have concluded that the formation of Cr-rich a¢-phase by Spinodal decomposition of d-ferrite phase is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of the formation of cleavage at ferrite and its propagation via separation of ferrite-austenite interphase. This article intends to provide an introductory overview on the thermal aging phenomena in LWR-relevant conditions. Firstly, the thermal aging effect on toughness is discussed in terms of the cause of embrittlement and influential parameters. An approximate analysis of thermal reaction using Arrhenius equation was carried out to scope the aging temperatures for the accelerated aging experiments to simulate the 60 and 80 years of services. Further, an equilibrium precipitation calculation was performed for model CASS alloys using the CALPHAD program, and the results are used to describe the precipitation behaviors in duplex stainless steels. These results are also to be used to guide an on-going research aiming to provide knowledgebased conclusive prediction for the integrity of the CASS components of LWR power plants during the service life extended up to and beyond 60 years.

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Section: Mechanism Of Thermal Embrittlement and Influential Factorsmentioning

confidence: 99%

Section: Mechanism Of Thermal Embrittlement and Influential Factorsmentioning

confidence: 99%

Thermal Aging Phenomena in Cast Duplex Stainless Steels

Byun

Yang

Overman

et al. 2015

JOM

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“…Few studies consider prolonged ageing at temperatures around 500°C and the interaction between evolving phases. Weiss and Stickler's time-temperature-precipitation diagram for aged Type 316H predicts only M 23 C 6 carbide formation under present ageing conditions [9].…”

Section: Discussionmentioning

confidence: 79%

“…For example, the presence of secondary phase precipitates, such as ferrite, has the potential to significantly alter the creep properties by changing the behaviour of creep damage accumulation [1][2][3][4][5]. The evolution of secondary phases during thermal ageing of Type 316 austenitic stainless steels has been observed experimentally [5][6][7][8][9] and predicted thermodynamically [10], driven by a favourable Gibbs energy [11]. These precipitates will nucleate at discrete sites within the overall microstructure and grow over time.…”

Section: Introductionmentioning

confidence: 99%

Precipitation within localised chromium-enriched regions in a Type 316H austenitic stainless steel

2018

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A Type 316H austenitic stainless steel component containing Cr and impurity element-rich localised regions arising from component fabrication was aged for a prolonged period during service at a temperature of approximately 550°C. These regions make up approximately 5% of the total volume of the microstructure. Previous work has shown that these regions contain ferrite and carbide precipitates and a finer austenite grain size than the adjacent matrix. The present study has used high-resolution transmission electron microscopy combined with compositional microanalysis to show that these regions have a highly complex microstructure containing G phase, chi phase and intragranular c 0 precipitates within the austenite grains. There is phosphorus migration to the chi austenite phase boundary, and the basis for this equilibrium impurity segregation is discussed. A Cr-depleted region was observed surrounding the chi phase precipitates, and the impact of this on the other precipitates is considered. The diversity of precipitates in these Cr-rich regions means that they behave significantly differently to the bulk material under long-term creep conditions leading to preferred nucleation and growth of creep cavities and the formation of localised creep cracks during service.

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“…It is well known that carbon can dissolve in χ phase and stabilize it. Due to this property, the χ phase was defined as M 18 C type carbide in the past [17,20].…”

Section: Microstructurementioning

confidence: 99%

Experimental and Thermodynamic Study of Selected in-Situ Composites from the Fe-Cr-Ni-Mo-C System

Wieczerzak

Bała

Dziurka

et al. 2016

Archives of Metallurgy and Materials

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The aim of the study was to synthesize and characterize the selected in-situ composites from the Fe-Cr-Ni-Mo-C system, additionally strengthened by intermetallic compounds. The project of the alloys was supported by thermodynamic simulations using Calculation of Phase Diagram approach via Thermo-Calc. Selected alloys were synthesized in an arc furnace in a high purity argon atmosphere using a suction casting unit. The studies involved a range of experimental techniques to characterize the alloys in the as-cast state, including optical emission spectrometry, light microscopy, scanning electron microscopy, electron microprobe analysis, X-ray diffraction and microhardness tests. These experimental studies were compared with the Thermo-Calc data and high resolution dilatometry. The results of investigations presented in this paper showed that there is a possibility to introduce intermetallic compounds, such as χ and σ, through modification of the chemical composition of the alloy with respect to Ni eq and Cr eq . It was found that the place of intermetallic compounds precipitation strongly depends on matrix nature. Results presented in this paper may be successfully used to build a systematic knowledge about the group of alloys with a high volume fraction of complex carbides, and high physicochemical properties, additionally strengthened by intermetallic compounds.

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Phase instabilities during high temperature exposure of 316 austenitic stainless steel

Cited by 731 publications

References 14 publications

Thermal Aging Phenomena in Cast Duplex Stainless Steels

Thermal Aging Phenomena in Cast Duplex Stainless Steels

Precipitation within localised chromium-enriched regions in a Type 316H austenitic stainless steel

Experimental and Thermodynamic Study of Selected in-Situ Composites from the Fe-Cr-Ni-Mo-C System

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