Solute Behavior in the Initial Nucleation of V- and Nb-Containing Carbide

Liu, Q. D.; Liu, W. Q.; Zhao, Shuyu

doi:10.1007/s11661-011-0783-z

Cited by 16 publications

(9 citation statements)

References 47 publications

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“…Early studies confirm that the carbide formed at the initial stage of tempering of the experimental steel is mainly vanadium enriched, although it also contains a little amount of niobium and molybdenum . The complex carbide in this study is considered as a later variation of coarsening MC‐type carbide.…”

Section: Discussionsupporting

confidence: 56%

“…At the initial nucleation stage, the plate‐like MC‐type carbide nuclei adopts the Baker–Nutting orientation relation in ferritic matrix, defined as (100) α‐Fe //(100) MC and [110] α‐Fe //[100] MC ,, and the relation keeps consistent during the growth and coarsening of the carbide to ellipsoidal or spherical shape. At the early stage of precipitation reaction, the MC‐type carbide has no certain crystal structure whereas it exists in the form of Fe‐enriched iso‐structure atmosphere and adopts B–N orientation relation with ferritic matrix in plate‐like shape, which is considered to largely reduce the misfit and elastic strain energy in aspect of composition and crystal structure. Different from the transient carbide, the misfit that exists between the ferritic matrix and the stoichiometric equilibrium MC‐type carbide is around 40% in the direction perpendicular to the (001) α‐Fe habit plane and around 10% in the direction parallel to the habit plane.…”

Section: Discussionmentioning

confidence: 99%

“…The nucleation manner largely reduces the misfit and elastic strain energy by newly appearance of boundary. The iso‐structure atmosphere is prone to exclude iron solute because vanadium and niobium have stronger affinity to carbon than iron and gradually evolves to VC or NbC equilibrium phase . During the coarsening process of the MC‐type carbide, besides the vanadium, the other carbide‐forming elements such as molybdenum and manganese tend to diffuse into the MC‐type carbide, leading to the formation of vanadium‐, manganese‐ and molybdenum‐enriched carbide inner core, as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Because of the existence of ferromagnetism in STEM and trajectory overlaps and local magnification in APT, atomic reconstruction of the carbide in complex steel is beyond the capability of the present instrument. However, many researchers have elucidated the compositional distribution in precipitates in multi‐component steel by three‐dimensional atom probe (3DAP) study and the structural changes of MC‐type carbides in model steels by high‐resolution transmission electron microscopy (HRTEM) study . Although the morphological, chemical and structural evolution of the alloy carbides has been evaluated in the literature, no satisfactory explanation is available yet on the precipitation kinetics of the complex alloy carbides.…”

Section: Introductionmentioning

confidence: 99%

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Compositional and structural characterization of alloyed carbide by 3D atom probe and high‐resolution TEM

Liu

Zhao

2013

Surface & Interface Analysis

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During tempering of solute supersaturated ferrous martensite, the face-centered cubic MC-type carbides (M is alloy elements) such as VC and NbC phases usually co-precipitate on crystal defects such as dislocation and take on plate-like morphology. Over-tempering makes the plate-like shape change to spherical shape because of Ostwald coarsening. The coarsening process strongly correlates to the diffusion behaviors of the carbon and carbide-forming elements, and consequently inhomogeneous compositional and structural distribution in the carbides is formed. Three-dimensional atom probe and high-resolution transmission electron microscopy have been proved useful methods to characterize the composition, morphology and nanostructure of the carbides that precipitate in a quench-tempered micro-alloyed steel. Depending on the actual affinity with C and the diffusion behavior, Si and Al are rejected from the alloy carbide, whereas Mn, V and Nb are inhomogeneously enriched in it. The morphology and structure change with the compositional redistribution. During the coarsening process of the pre-existing plate-like carbide, transition carbide that is semi-coherent with ferritic matrix is formed because of the disparity in diffusion ratio of different solutes. A core-shell complex nanostructure is consequently formed in the coarsening carbide, and the core and shell are identified as V 8 C 7 enriched in Mn, Mo and Mo 2 C, respectively.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Compositional and structural characterization of alloyed carbide by 3D atom probe and high‐resolution TEM

Liu

Zhao

2013

Surface & Interface Analysis

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“…The solute Nb atoms gave rise to a strong solute drag effect, preventing grain boundary migration and inhibiting the grain growth [28,29], leading to the refinement of austenite grains. The fine grains resulted in an improvement in hardness at the center of the TS samples, as shown in Figure 9.…”

Section: Segregation and Propertiesmentioning

confidence: 99%

Thermal Simulation Study on the Solidification Structure and Segregation of a Heavy Heat-Resistant Steel Casting

Wang

Zhong

et al. 2019

Metals

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The prediction and controlling of the solidification structure and macro-segregation in heavy steel casting, which is usually produced in limited quantities, was a conundrum in the foundry field. In this work, the cooling and solidification processes of a 16 t CB2 ferritic heat-resistant steel (FHRS) valve casting were reproduced by studying the solidification behavior of three typical units through a thermal simulation method. The results indicate that the types of casting without chilling have the most uneven distribution of solutes and hardness, while those types of casting in which parts are solidified by chilling are much more uniform. The macro-segregation degrees of B, C, Nb, P, Cr, Mo, Si, V and Mn decrease gradually during heavy casting of CB2 ferritic heat-resistant steel. Of them, B, C, Nb, and P are solutes prone to segregation, and the maximum macro-segregation index of B can even reach 15. The macro-segregation tendencies of Cr, Mo, Si, V, and Mn are relatively small. Further studies on the last solidification portion of samples taken by electron microprobe reveal that large-sized precipitates such as MnS and NbxC are easily formed due to solute enrichment, and the sizes of these precipitates were distributed from dozens to hundreds of micrometers.

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Microstructure Stabilities of Newly Developed Hot‐Working Die Steel and H13 Steel at Elevated Temperature

Zhang

Cao

Chen

et al. 2023

steel research int.

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Hot-working die steels have an important role in the development of the industry and society, and they are widely used in industrial manufacturing due to their good mechanical properties, wear resistance and thermal resistance. [1][2][3][4] With the rapid increase in industrial and manufacturing requirements, dies need to operate under severe conditions of high temperature and pressures. The peak temperature at the surface of dies can reach even 700 °C, and exceed the tempering temperature. This inevitably leads to an evolution of the microstructure and degradation of mechanical properties, such as the hardness, strength, and thermal fatigue properties, strongly related to the service life of dies. [4,5] Therefore, the microstructure stability of hot-working die steels is of significance.The martensite lath structure is in a metastable state with a low thermal stability. The strength and hardness of the steel rapidly decrease with the recovery and disappearance of the lath structures in a martensitic steel. [6][7][8] Alloying with high levels of alloying elements is usually regarded as an effective approach to improve the thermal stability of a metallic material, but it is not a universally applicable method and is not conducive to some important properties of steels. For example, Cr is an important alloying element in a heat-resistant steel, and 9-12% Cr is usually added in the heat-resistant steel to form M 23 C 6 carbides always distributed along lath boundaries and grain boundaries to hinder their migration and recrystallization during creep. [9,10] However, the M 23 C 6 carbide is not conducive to the thermal fatigue performance and thermal stability of hot-working die steels owing to its fast coarsening. [5,11] The growth rate of M 7 C 3 in low-Cr alloys is slower than that of M 23 C 6 , which can be used as a type of precipitation pinning the microstructure interface. [12,13] Owing to the excellent thermal stability, the MC carbide can effectively hinder the recovery and recrystallization of the microstructures at temperatures lower than 600 °C. [14] Moreover, at a temperature below 0.5 T m , the deformation mechanism of steel materials is still the slip of dislocations. The stable and fine MC carbide can provide an excellent strengthening effect for the matrix under high-temperature conditions. [15,16] Therefore, the typical microstructures of hot-working die steels contain carbide forming elements such as Cr, Mo, and V to form the fine dispersed MC or M 2 C nano-carbides. [17] However, the microstructures of the present commercial hot-working die steels still becomes unstable when the temperature is increased to 600-650 °C. [6,11] In a previous study, a Cr-Mo-W-V HWD700 steel was developed, which exhibits a high strength as well as excellent fatigue performance at temperatures up to 700 °C strengthened by MC (M = V, Mo, W) nano-carbides. [18][19][20] However, the microstructure stability of the HWD700 steel at an elevated temperature has not been extensively investigated. In this study, the

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Solute Behavior in the Initial Nucleation of V- and Nb-Containing Carbide

Cited by 16 publications

References 47 publications

Compositional and structural characterization of alloyed carbide by 3D atom probe and high‐resolution TEM

Compositional and structural characterization of alloyed carbide by 3D atom probe and high‐resolution TEM

Thermal Simulation Study on the Solidification Structure and Segregation of a Heavy Heat-Resistant Steel Casting

Microstructure Stabilities of Newly Developed Hot‐Working Die Steel and H13 Steel at Elevated Temperature

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