Influence of Heat Treatment Time and Temperature on the Microstructure and Corrosion Resistance of Cast Superaustenitic Stainless Steels

DuPont, J. N.; Farren, Jeffrey D.

doi:10.5006/1.3586019

Cited by 7 publications

(4 citation statements)

References 8 publications

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“…1c). This was repeated five more times, producing a total of six [12], who found complete dissolution of the sigma phase and homogenization of Mo only happened after a heat treatment of 1205 °C for 4 h. This same study also found that this heat treatment produces corrosion resistance of CN3MN and CK3MCuN cast alloys on the level of their wrought counterpart alloys [12]. Thus, by using an even higher temperature than suggested by Dupont, it was assumed any differences seen in phase formation between samples cooled at similar rates could only be due to residual differences in the initial microstructure produced by the selected solidification rates.…”

Section: Methodsmentioning

confidence: 99%

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Influence of cooling rate on the ferrite content and microstructures in CD3MWCuN castings

Liao

Chumbley

2018

SN Appl. Sci.

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Highly alloyed CD3MWCuN was chosen to investigate the influence of cooling rates on the ferrite content of duplex stainless steels. It is known that cooling rate can influence the overall ferrite/austenite ratio, and achieving the proper balance of phases is crucial in producing a casting with suitable mechanical and corrosion properties. Initial experiments were carried out to study the ferrite/austenite ratio as a function of cooling involved samples obtained using different cooling rates through the solidification temperature as well as different cooling rates from the homogenization temperature. A single keel bar was obtained, sectioned, and recast at six different solidification cooling rates. Each of the six castings was then sectioned into six pieces and each piece cooled from the homogenization temperature to produce six different homogenization cooling rates. Backscattered electron imaging was used to measure the phase percentages and observe the microstructures. The ferrite content was found to increase with increasing homogenization cooling rates. It was also found that the homogenization cooling rate should be higher than 200 °C/h in order to get high ferrite contents (> 40%). As the cooling rate slows, intermetallic phases such as sigma start to precipitate at the grain boundaries.

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Section: Methodsmentioning

confidence: 99%

“…The ferrite content after solidification was not measured in this paper since the cast alloy studied is always homogenized before use. This is necessary to completely dissolve any sigma phase that may have formed upon cooling and to produce homogenization of the Mo, which can be difficult [12].…”

Section: Solidification Ratementioning

confidence: 99%

Influence of cooling rate on the ferrite content and microstructures in CD3MWCuN castings

Liao

Chumbley

2018

SN Appl. Sci.

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“…It has been reported that a high content of Mo enhances the formation of Mo-rich intermetallics, such as sigma and chi phases, degrading the formability of the cast billet and inducing cracking of the cast billet in subsequent hot/cold wire drawings [ 13 , 14 ]. Therefore, homogenization heat treatment of the cast 316L billet is required before hot drawing [ 13 , 15 , 16 , 17 , 18 ]. The distribution and morphology of δ-ferrite and sigma phases in the austenite matrix of the 316L cast billet are strongly related to the subsequent hot and cold wire drawing of the cast billet.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Homogenization Heat Treatment on 316L Stainless Steel Cast Billet

Chu,

Shiue,

Cheng

2023

Materials

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This investigation aims to analyze the effect of homogenization heat treatment at 1240 °C for 2 and 6 h on the hardness, distribution, morphology, and chemical composition of the δ-ferrite and sigma phases in 316L stainless steel cast billet. A field emission scanning electron microscope, combined with electron back-scattered diffraction, a field emission electron probe microanalyzer with a wavelength dispersive spectrometer, and a Vickers microhardness tester are applied to identify various phase evolutions in the cast billet. The morphology of the δ-ferrite and sigma phases in the austenite matrix of the 316L cast billet are strongly related to the subsequent hot and cold wire drawings. The homogenization heat treatment is expected to provide a driving force to form spheroid interdendritic δ-ferrite and to minimize the amount of the brittle sigma intermetallic compound in the austenite matrix. The homogenization heat treatment at 1240 °C effectively spheroidized all δ-ferrites into blunt ones in the cast billet. The transformation of δ-ferrite into sigma is dominated by temperature and cooling rate. The fast air cooling after homogenization between 1240 and 850 °C retards the precipitation of the sigma in the δ-ferrite. There are two δ-ferrite transformation mechanisms in this experiment. The direct transformation of the δ-ferrite into sigma is observed in the as-cast 316L stainless steel billet. In contrast, the eutectoid transformation of the δ-ferrite into the sigma and austenite dominates the 316L cast billet homogenized at 1240 °C, with a slow furnace cooling rate.

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“…It has been reported that a high content of Mo enhances the formation of Mo-rich intermetallics, such as sigma and chi phases, degrading mechanical properties and encouraging hot cracking [13,14]. Therefore, homogenization heat treatment of the cast 316L billet is necessary before hot forging the cast billet [13,[15][16][17][18]. The distribution and morphology of δ-ferrite and sigma phases in the austenite matrix of the 316L cast billet are strongly related to following hot/cold forging of the cast billet.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Homogenization Heat Treatment on 316 Stainless Steel Cast Billet

Chu,

Shiue,

Cheng

2023

Preprint

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The investigation aims to analyze the effect of homogenization heat treatment on the quantity, distribution, morphology, and chemical composition of δ ferrite and sigma phase in the 316L austenitic stainless steel cast billet. Microstructures of the cast billet at different locations, center, 0.5 R, R, and the subsequent 2/6-hour homogenization heat treatment at 1240 oC were examined. The microstructure at the radius R was much more uniform and expected a better performance in the following hot/cold forging processes due to the highest cooling rate compared with those at 0.5R and center. The δ ferrite often accompanies the generation of the sigma phase, and the transformation of δ ferrite into the sigma/(austenite) and retained δ ferrite is strongly related to the cooling rate after homogenization heat treatment. The sigma phase is hard and detrimental to the subsequent hot/cold forgings. It must be removed from the homogenization heat treatment before forging. Fast air cooling from 850 oC to room temperature after homogenization heat treatment cannot prohibit the sigma phase formation. Rapid cooling between 850 and 1240 oC after homogenization treatment is required to avoid the sigma phase formation in the 316L stainless steel cast billet.

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Influence of Heat Treatment Time and Temperature on the Microstructure and Corrosion Resistance of Cast Superaustenitic Stainless Steels

Cited by 7 publications

References 8 publications

Influence of cooling rate on the ferrite content and microstructures in CD3MWCuN castings

Influence of cooling rate on the ferrite content and microstructures in CD3MWCuN castings

The Effect of Homogenization Heat Treatment on 316L Stainless Steel Cast Billet

The Effect of Homogenization Heat Treatment on 316 Stainless Steel Cast Billet

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