Evolution of secondary phases 12% Cr steel during quenching and tempering

Janovec, Jozef; Svoboda, Milan; Blach, J.

doi:10.1016/s0921-5093(98)00526-7

Cited by 38 publications

(12 citation statements)

References 20 publications

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“…10,11) The size and morphology of the Nb-rich MX particles suggested that they were undissolved precipitates during austenitization. Similar precipitates were observed by Jones et al in 9Cr-1Mo steel 5) and Janovec et al in 12Cr steel 12) as well. This meant that the austenitization at 1080°C for 16 h was insufficient to dissolve all of the precipitates.…”

Section: Mechanical Testssupporting

confidence: 89%

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Tao

Han

2015

Mater. Trans.

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The effect of the quenching rates on microstructure and impact ductile of X12CrMoWVNbN10-1-1 steel was investigated. The samples were heated to 1080°C for 16 h and quenched with different rates to room temperature, then tempered at 700°C for 24 h. It was found that the critical quenching rate of suppressing the precipitation of Cr-rich M 2 N and Fe-rich M 3 C was faster than 1.5°C/min and 10°C/s, respectively. And the critical quenching rate for the precipitation of ferrite was in the range of 1³1.5°C/min. The impact energy began to decrease when the tempered sample was quenched with a rate of 1.5°C/min due mainly to the precipitation of Cr-rich M 2 N based on the careful conducted analysis of the microstructure and fractography.

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Section: Mechanical Testssupporting

confidence: 89%

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Tao

Han

2015

Mater. Trans.

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“…9) Such two-phase separation behavior has been clearly demonstrated by experimental results during tempering heat treatment at 765°C in a 9Cr-1Mo-V-Nb steel by Suzuki et al 10) Since MX particles are major strengthener, precipitation behavior in cooperate with two-phase separation of those during normalizing and tempering heat treatment strongly influences on creep strength. However, it has not yet been clearly understood, and presence of cementite (M 3 C) in the as normalized condition in 9-12Cr ferritic creep resistant steels [12][13][14][15][16][17] has not yet been authorized. Aim of the present study is to understand phase equilibrium between austenite and MX carbonitride at the elevated temperature in a 9Cr-1Mo-V-Nb steel and influence of normalizing temperature on the precipitates in the as normalized condition has been investigated.…”

Section: Introductionmentioning

confidence: 99%

Phase Equilibrium between Austenite and MX Carbonitride in a 9Cr-1Mo-V-Nb Steel

et al. 2005

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Precipitation behavior during normalizing heat treatment has been investigated on a 9Cr-1Mo-V-Nb steel. Heterogeneously distributed spherical MX (MϭNb, V, Cr and XϭC, N) carbonitride particles and platelet M 3 C (MϭFe, Cr) carbide were observed in the as normalized condition. Number of the precipitates decreased with increasing normalizing temperature and no precipitates was observed after normalizing at 1 250°C. Although the size of M 3 C was almost constant independent of normalizing temperature, that of MX increased with increase in normalizing temperature up to 1 200°C. For MX carbonitride, not only size, but also composition of metallic elements was influenced by normalizing temperature. Since equilibrium composition of MX carbonitride depends on temperature, MX particle with non-equilibrium composition dissolves and precipitation of it takes place with its equilibrium composition at the normalizing temperature. A phase field diagram of NbX-VX quasi binary system in a 9Cr-1Mo-V-Nb steel was experimentally determined. It has been supposed that precipitation of M 3 C takes place during cooling from normalizing temperature in the surrounding area of MX particles where the concentration of niobium and vanadium in matrix is poor.KEY WORDS: ferritic creep resistant steel; 9Cr-1Mo-V-Nb steel; MX carbonitrides; cementite; phase equilibrium; precipitation behavior; two-phase separation; normalizing.quency vacuum induction furnace. The ingot was heated to 1 150°C for 1.5 h and hot rolled in a range of temperatures from 1 150°C to 900°C into bar with a diameter of 16 mm. Normalizing heat treatment conditions are shown in Table 2, together with prior austenite grain size number and Vickers hardness in the as normalized condition. Normalizing heat treatments were performed for 600 s in a range of temperatures from 1 050 to 1 250°C and for 3 600 s at 1 100 and 1 200°C, followed by air cooling. Prior austenite grain size of the steel coarsened with increase in normalizing temperature, but hardness of about HV400 was almost the same independent of normalizing temperature. Presence of d-ferrite was not detected for all the normalizing temperatures investigated.Distribution of precipitates was observed on carbon extracted replica under Field Emission Transmission Electron Microscope (FE-TEM). Each precipitates were analyzed by Energy Dispersion X-ray Spectroscopy attached to FE-TEM (TEM-EDS). Mechanically polished specimen surface was etched in a saturated solution of picric acid in ethyl alcohol with 1 % hydrochloric acid (Villela's reagent). The carbon was deposited on the etched surface, and the carbon film was detached from the specimen surface in a Villela's reagent. The carbon extracted replica was cleaned in ethyl alcohol and collected on copper grids for TEM examination. Precipitates were identified by means of X-ray diffraction analysis on an electrolytically extracted residue. Figure 1 shows a TEM micrograph of the carbon extracted replica prepared from the steel in the as received condition. Figure 1(b) is a high...

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“…Precipitation or dispersion hardening (mainly attributed to M 23 C 6 and MX particles) were generally formed at tempering stage, where M denotes a substitutional component, and X is carbon or nitrogen atoms, which is one of the most important strengthening methods in T91 ferritic heat‐resistant steel. The precipitation mechanism and evolution process of these particles during tempering has been studied extensively 10–15. However, the precipitation behavior during the early stage of tempering is rarely reported.…”

Section: Introductionmentioning

confidence: 99%

Effect of M₃C on the Precipitation Behavior of M₂₃C₆ Phase during Early Stage of Tempering in T91 Ferritic Steel

Liu

Zhang

et al. 2011

steel research int.

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Tempered martensitic structure is the service condition of T91 ferritic steel after adopting the austenitizing followed by tempering. Needle‐like M3C particles are precipitated during air cooling after austenization, while the precipitation of M3C is suppressed during the water cooling. The effect of existence of M3C on the precipitation behaviors of M23C6 during the early stage of tempering, as nucleation site, number density and size distribution, was investigated by means of TEM observation. The TEM results indicate that, upon the same tempering time, the size of M23C6 is smaller and its number density is higher in the sample pre‐existing M3C than in the sample without M3C. This can be explained that existence of M3C results in more M23C6 precipitates forming inside of grain, where a relatively low self‐diffusion coefficient of alloy element leads to M23C6 hardly coarsening. However, with the prolongation of tempering time, this effect becomes weaken. Microhardness results indicate that the existence of M3C phase results in the increase of hardness after tempering due to the precipitation of finer and denser M23C6 particles.

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Evolution of secondary phases 12% Cr steel during quenching and tempering

Cited by 38 publications

References 20 publications

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Phase Equilibrium between Austenite and MX Carbonitride in a 9Cr-1Mo-V-Nb Steel

Effect of M₃C on the Precipitation Behavior of M₂₃C₆ Phase during Early Stage of Tempering in T91 Ferritic Steel

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Evolution of secondary phases 12% Cr steel during quenching and tempering

Cited by 38 publications

References 20 publications

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

Phase Equilibrium between Austenite and MX Carbonitride in a 9Cr-1Mo-V-Nb Steel

Effect of M3C on the Precipitation Behavior of M23C6 Phase during Early Stage of Tempering in T91 Ferritic Steel

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Effect of M₃C on the Precipitation Behavior of M₂₃C₆ Phase during Early Stage of Tempering in T91 Ferritic Steel