High temperature ageing behaviour of a duplex stainless steel

Ghosh, S. K.; Mondal, Subhash Chandra

doi:10.1016/j.matchar.2008.04.008

Cited by 106 publications

(63 citation statements)

References 20 publications

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“…2 h/700°C [22], 1 h/750°C [22], 2 h/750°C [26], 30 min/780°C [27] and 30 min/800°C [28] ). Although the formation of chi phase in duplex steels is often initially favoured over that of sigma phase, sigma-phase formation is favoured over longer ageing periods [27] with chi phase having been observed to transform into sigma phase following further ageing [22,26,27].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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In this study, the evolution of sigma-phase development in a 2205 duplex steel was studied following thermal ageing in the temperature range 750-850°C for periods up to 100 h. A suite of materials analysis techniques including combined electron backscatter diffraction-energy-dispersive X-ray imaging and magnetic force microscopy are used to quantify the change in volume fraction of the phases. The experimental results for each ageing condition are compared with the results from other ageing experiments and the predictions from the computer modelling. They show good correlation for the amount of sigma phase formed under a range of ageing conditions (and thus varying quantities of sigma phase). EBSD measurements showed no preferential orientation relationships relative to the parent ferrite for the nucleation of sigma phase, implying that the minimisation of boundary misorientation energy is not significant in determining sigma-phase nucleation sites. The results are discussed with respect to the experimentally measured properties of sigma phase and the kinetics of the precipitation process.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…However, given that chi phase is typically formed in the high Cr d-ferrite rich regions, duplex steels or Type 300 series weld metal may provide a better basis for comparison. Assuming this to be the case, there have been observations of chi phase after only 5000 h at 500°C [31] and rapid chi phase precipitation at 600°C [30,34,43] suggests that evolution will have occurred during the service life of the material. Hence, the initial nucleation of chi phase occurs during service; however, further precipitates may nucleate and grow during the post-service heat treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Depending on the relative concentrations of Mo and Ti, the composition of the chi phase ranges from (Fe/Ni) 36 [12,24,[26][27][28], and there is potential for substitution of other elements [28]. The composition of chi phase is frequently likened to that of sigma phase, with the principle differences being the solubility of carbon [12,26] and higher concentrations of molybdenum [26,29,30]. Chi phase has been observed to nucleate and grow preferentially into the ferrite regions of dual phase (austenite-ferrite) steels [26,[29][30][31][32], at grain boundaries of d-ferrite [26,32], at austenite-dferrite grain edges and nodes [32] and austenite-dferrite phase boundaries [29,30,32].…”

Section: Introductionmentioning

confidence: 99%

“…The composition of chi phase is frequently likened to that of sigma phase, with the principle differences being the solubility of carbon [12,26] and higher concentrations of molybdenum [26,29,30]. Chi phase has been observed to nucleate and grow preferentially into the ferrite regions of dual phase (austenite-ferrite) steels [26,[29][30][31][32], at grain boundaries of d-ferrite [26,32], at austenite-dferrite grain edges and nodes [32] and austenite-dferrite phase boundaries [29,30,32]. This preference has been linked to the greater concentrations of Cr and Mo present in ferrite, and the higher rate of diffusion of these BCC elements through the ferrite (BCC) as opposed to the austenite (FCC) [31].…”

Section: Introductionmentioning

confidence: 99%

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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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“…Furthermore, the χ phase is enriched in Cr and Mo in comparison with the matrix [21][22][23], which explains why it is visible as a bright phase in BSE contrast. The formation of χ phase results from the high supersaturation of first crystals, as a consequence of non-equilibrium solidification with a relatively high cooling rate.…”

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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High temperature ageing behaviour of a duplex stainless steel

Cited by 106 publications

References 20 publications

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

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

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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