Review of stabilisation of ferritic stainless steels

Gordon, W.; Bennekom, A. van

doi:10.1179/026708396790165579

Cited by 13 publications

(12 citation statements)

References 3 publications

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“…1(b) of which the presence of the main constituent of Laves phase plus smaller amounts of (Ti,Nb)(C,N) were confirmed by XRD from the electrolytically extracted second phases. Angular carbo-nitrides of titanium and niobium observed here by both SEM and TEM, were also found to be randomly dispersed throughout the structure and these lower the melting point of the steel [15]. Excess niobium is taken into solid solution during high temperature annealing and is re-precipitated as very fine particles of the Laves phase (Fe 2 Nb) upon either slow cooling or upon holding at intermediate temperatures of 600-950 • C [16], leading to improved elevated temperature strength [17,18].…”

Section: Types Of Precipitates Found In Type Aisi 441mentioning

confidence: 73%

Laves phase embrittlement of the ferritic stainless steel type AISI 441

Sello

Stumpf

2010

Materials Science and Engineering: A

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Section: Types Of Precipitates Found In Type Aisi 441mentioning

confidence: 73%

Laves phase embrittlement of the ferritic stainless steel type AISI 441

Sello

Stumpf

2010

Materials Science and Engineering: A

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“…It has been indicated that in ferritic stainless steels, sensitization takes place after exposure to the temperature above 925 • C, 13 which is considered to be due to chromiumdepleted zones resulting from chromium carbides and nitrides precipitated along the grain boundaries. [12][13][14][15] Also in the water-quenched material in this study, it is believed that chromium-depleted zones that have low strength would be formed along the grain boundaries, which may be the cause for the reduction in fatigue strength. Hodges has pointed out that the sensitization occurs in high purity ferritic stainless steels.…”

Section: Reduction In Fatigue Strength In Laboratory Airmentioning

confidence: 84%

Effects of annealing and quenching on fatigue behaviour in type 444 ferritic stainless steel

Akita

Nakajima

Uematsu

et al. 2008

Fatigue Fract Eng Mat Struct

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A B S T R A C T In order to understand the effects of annealing and quenching on fatigue behaviour in type 444 stainless steel, fully reversed axial fatigue tests have been performed using smooth specimens of heat-treated materials in laboratory air and 3%NaCl aqueous solution.Three materials subjected to different heat treatments, annealing at 960 and 1000 • C, and water-cooling at 960 • C, were prepared. In laboratory air, the fatigue limit of the annealed specimens was lower than that of the as-received specimen and decreased with increasing annealing temperature. The subsequent grain coarsening from the heat treatments was primarily responsible for the lower fatigue strength in the annealed specimens. The fatigue strength of the water-cooled specimen was lower than that of the corresponding annealed specimen. In the annealed specimens, cracks were generated within ferritic grains, while in the water-cooled specimen, at or near grain boundaries. In 3%NaCl solution, the fatigue strengths of all specimens decreased compared with those in laboratory air. Only in the water-cooled specimens, crack initiation at grain boundary and intergranular crack growth were observed, indicating the most sensitive to corrosion environment.Because ferritic stainless steels with extremely reduced interstitial content possess excellent resistance to stress corrosion cracking, good toughness, ductility and weldability, as compared with conventional austenitic stainless steels, 1,2 their applications to structural components in machines and structures are increasing, particularly in elevated temperature applications such as exhaust system products of automobiles. 3 In such components, it is expected that grain growth and sensitization would take place due to frequent heating and cooling at the temperature range above recrystallization temperature. Thus evaluation on the fatigue properties of materials subjected to annealing and quenching becomes extremely important in order to ensure their safety and reliability. For several years, we have studied on type 444 ferritic stainless steel, 4-8 while in newly developed high purity ferritic stainless steels, the studies on the fatigue behaviour of the steels heated above the sensitizing temperature, usually Correspondence: K. Tokaji.above 900 • C, have been very limited. 9 For increasing practical use, such a condition is unfavourable from the viewpoint of the safety and reliability. The present paper gives the result of fatigue testing on the ferritic stainless steel, which was heated above the sensitizing temperature, i.e. fully reversed axial fatigue tests have been performed on materials annealed at 960 and 1000 • C and water-quenched at 960 • C of type 444 ferritic stainless steel in laboratory air and 3%NaCl solution. The effects of heat treatment on fatigue behaviour were discussed on the basis of crack initiation, small crack growth and fractographic analysis. E X P E R I M E N T A L D E T A I L S MaterialThe material used is a high purity ferritic stainless steel, type 444 (18Cr-2M...

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“…[20] However, low concentrations of C and N, which are unavoidable during steel production, decrease the solvus temperature of the Laves phase due to the high affinity of Nb for C and N, thus leading to the formation of carbides/nitrides instead of the Laves phase. [21] Microalloying with Ti minimizes primary precipitation of niobium nitrides and niobium carbides, so that this element is still available for Laves phase formation.…”

Section: A Alloy Designmentioning

confidence: 99%

Evolution of the Laves Phase in Ferritic Heat-Resistant Steels During Long-term Annealing and its Influence on the High-Temperature Strength

Nabiran

Klein

Weber

et al. 2014

Metall Mater Trans A

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Heat-resistant ferritic steels containing Laves phase precipitates were designed supported by thermodynamic modeling. High-temperature compression tests at 1173.15 K (900°C) and a detailed characterization of the microstructural evolution during annealing at 1173.15 K (900°C) were carried out to investigate the effect of Laves phase formation on the high-temperature strength. Due to the addition of W/Mo and/or Nb, the high-temperature strength of the newly designed alloys is significantly higher than that of the reference steels. However, the high-temperature strength of all investigated steels decreases slightly as the annealing time is increased up to 1440 hours. To determine the influence of Laves phase formation and coarsening on the high-temperature strength during long-term annealing, the precipitates were extracted from the ferritic matrix in different annealing states. The phases in the powder residue were determined by XRD, and the chemical composition of the Laves phase in dependence of the annealing time was analyzed by EDS measurements.

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Review of stabilisation of ferritic stainless steels

Cited by 13 publications

References 3 publications

Laves phase embrittlement of the ferritic stainless steel type AISI 441

Laves phase embrittlement of the ferritic stainless steel type AISI 441

Effects of annealing and quenching on fatigue behaviour in type 444 ferritic stainless steel

Evolution of the Laves Phase in Ferritic Heat-Resistant Steels During Long-term Annealing and its Influence on the High-Temperature Strength

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