Carbide precipitation in Nb-V-Ti microalloyed ultra-high strength steel during tempering

Dong, Ji; Zhou, Xiaosheng; Liu, Yongchang; Li, Chong; Liu, Chenxi; Guo, Qianying

doi:10.1016/j.msea.2016.12.019

Cited by 110 publications

(52 citation statements)

References 36 publications

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“…When the tempering temperature is over 690 • C, the M 8 C 7 type carbides almost disappear. Thus, the carbide precipitation sequence is M 8 C 7 → M 3 C. It is noteworthy that the presence of M23C6 carbides is not observed in our experiment, whereas the existence of this type of carbide in other low alloy Cr-Mo steel after tempering is reported in published literature [24,25]. The precipitation temperatures of V-rich M8C7 and Cr-rich M23C6 are calculated to explain the difference.…”

Section: Microstructurescontrasting

confidence: 47%

Effect of Tempering Temperature on the Low Temperature Impact Toughness of 42CrMo4-V Steel

Sun

Liu

et al. 2018

Metals

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Effects of tempering temperature on the microstructures and low temperature impact toughness of 42CrMo4-V steel were investigated. Microstructures of 42CrMo4-V steel after tempering at 570-720 • C for 3 h were experimentally investigated using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the carbide precipitation sequence of 42CrMo4-V steel is M 8 C 7 → M 3 C and the absorbed energies of 42CrMo4-V steel increase greatly from 21.7 J to 132.3 J with increasing tempering temperature from 570 • C to 720 • C. The changes of impact toughness with increasing tempering temperature were attributed to the softening of matrix, the evolution of carbide precipitates and grain structures.

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Section: Microstructurescontrasting

confidence: 47%

Effect of Tempering Temperature on the Low Temperature Impact Toughness of 42CrMo4-V Steel

Sun

Liu

et al. 2018

Metals

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“…At different tempering temperatures, two types of MC carbides existed steadily. It was suggested that the mechanisms of M 3 C and two types of MC nucleation agree with a type of 'separate nucleation', and the mechanisms of the M 2 C, M 23 C 6 and M 7 C 3 nucleation are likely to be of 'in situ transformation' type [24]. Two types of MC carbides were found to be stable phases existing over a wide temperature range [24].…”

Section: Discussionmentioning

confidence: 98%

“…There are many research papers related to carbides precipitation and transformation both during the steel heat treatment and during long-term operation of elements at elevated temperatures [22][23][24][25]. Liu et al [22] investigated various austenitization conditions (holding time, temperature and the subsequent cooling rate), which were used to clarify the effect of normalizing conditions on the formation of the M 3 C phase.…”

Section: Discussionmentioning

confidence: 99%

“…After tempering for 100 h, only M 23 C 6 carbides remained, which number, density, and size kept increasing throughout 30 min to 100 h owing to their high thermostability. Dong et al [24] identified four kinds of precipitates (M 3 C, M 2 C, M 23 C 6 and M 7 C 3 ) at different tempering temperatures. At the tempering temperatures ranging from 200 to 400°C, M 3 C precipitated first.…”

Section: Discussionmentioning

confidence: 99%

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Microstructure changes responsible for the degradation of the 10CrMo9-10 and 13CrMo4-5 steels during long-term operation

Gwoździk

Motylenko

Rafaja

2019

Mater. Res. Express

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The paper presents results of microstructure and mechanical testing examinations performed using optical and transmission electron microscopy, tensile tests and Charpy tests on 10CrMo9-10 and 13CrMo4-5 steels, before and after they were long-term operated at elevated temperatures in a steam heater. In the 10CrMo9-10 steel, the optical microscopy detected a degradation of original bainite that was accompanied by the formation of ferrite, precipitates and micropores. The transmission electron microscopy revealed that the precipitates are M 23 C 6 and M 7 C 3 type carbides, which are located mainly at the boundaries of former austenite grains, and M 3 C type carbides, which appear inside the grains. The 13CrMo4-5 steel contained a relatively high amount of ferrite in the ferritic-bainitic/perlitic microstructure already in the originally state. The degradation of the microstructure was less serious than for the 10CrMo9-10 steel. The thermal treatment of the 13CrMo4-5 steel led mainly to the precipitation of carbides. The M 23 C 6 and M 7 C 3 type carbides form in perlitic-bainitic areas, while M 3 C and M 6 C type carbides precipitate in ferrite. The higher density of the grain boundary precipitates in the long-term operated 10CrMo9-10 steel facilitated the formation of creep-induced micropores and contributed to the hardness reduction.

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“…The results show that the particle in Figure 7b,c is the M 23 C 6 carbides with the face-centered cubic crystal structure. The larger irregular block M 23 C 6 carbides will be precipitated along the grain and subgrain boundaries when the tempering temperature is above 500 • C [28]. Further, a large spherical particle in Figure 7a,d is identified to be the M 7 C 3 carbides with the hexagonal close-packed crystal structure.…”

Section: Influence Of Re Addition On the Tempered Carbidesmentioning

confidence: 93%

Carbides Evolution and Tensile Property of 4Cr5MoSiV1 Die Steel with Rare Earth Addition

Liu

et al. 2017

Metals

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Studies of 4Cr5MoSiV1 die steel suggest that under appropriate conditions, additions of rare earth (RE) can enhance tensile property. This improvement is apparently due to the more uniform distribution of carbides and the enhancement of precipitation strengthening after RE additions. In this present work, the effect of the RE addition on the carbides evolution and tensile property of 4Cr5MoSiV1 steel with various RE contents (0, 0.018, 0.048 and 0.15 wt %) were systematically investigated. The two-dimensional detection techniques such as optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to investigate the carbides evolution of as-cast, annealed and tempered with RE addition. The results indicated that the carbides in 4Cr5MoSiV1 steels were modified by adding the suitable amount of RE. The eutectic structure and coarse eutectic carbides were all refining and the morphology of the annealed carbides initiated change from strip shape to ellipsoidal shape compared with the unmodified test steel (0RE). In addition, the amount of the tempered M 8 C 7 carbides increased initially and then decreased with the alteration of RE addition from 0.018 to 0.15 wt %. Notably, the tensile test indicated that the average value of ultimate tensile strength (UTS) and elongation rate of 0.048RE steel increased slightly to 1474 MPa and 15%, higher than the 1452 MPa and 12% for the unmodified test steel (0RE), respectively. Such an addition of RE (0.048 wt %) would have a significant effect on the carbides evolution of as-cast, annealed and tempered and resulting in the tensile property of 4Cr5MoSiV1 die steel.

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Carbide precipitation in Nb-V-Ti microalloyed ultra-high strength steel during tempering

Cited by 110 publications

References 36 publications

Effect of Tempering Temperature on the Low Temperature Impact Toughness of 42CrMo4-V Steel

Effect of Tempering Temperature on the Low Temperature Impact Toughness of 42CrMo4-V Steel

Microstructure changes responsible for the degradation of the 10CrMo9-10 and 13CrMo4-5 steels during long-term operation

Carbides Evolution and Tensile Property of 4Cr5MoSiV1 Die Steel with Rare Earth Addition

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