Journal articles: 'M23C6'

1

Zhao, Hongchang, Zixi Wang, Xi Han, and Mingjia Wang. "Effect of Long-Term Aging on the Microstructural Evolution in a P91 Steel." Materials 15, no. 8 (April 13, 2022): 2847. http://dx.doi.org/10.3390/ma15082847.

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The precipitation and growth mechanism of the Laves phase and the coarsening behaviors of Laves phase, M23C6 and MX carbonitrides have been emphatically investigated in P91 steel at 625 °C under different aging conditions. After long-term aging at 625 °C (>1500 h), it was observed that the Laves phase grew rapidly in the region near the M23C6 carbide once precipitated, and further gradually completed the engulfment process until the M23C6 carbide particles disappeared. Furthermore, a new crystallographic orientation relationship between M23C6 carbides and Laves phase has been observed at 625 °C for 5000 h, which is {0001}Laves∥{111}M23C6, <112¯1>Laves∥ <011>M23C6. The coarsening behaviors of Laves phase, M23C6 carbides and MX carbonitrides have been emphatically investigated, conforming to the existing ripening model of multicomponent alloys. The coarsening rates for the Laves phase, M23C6 and MX have values of ~32.2 (≥5000 h), 5.3 and 0.6 nm/h1/3, respectively.

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2

Kim, Hong-Pyo, Yun-Min Park, Hyoung-Min Jang, Sang-Yeob Lim, Min-Jae Choi, Sung-Woo Kim, Dong-Jin Kim, Seong-Sik Hwang, and Yun-Soo Lim. "Early-Stage M23C6 Morphology at the Phase Boundary in Type 304L Austenitic Stainless Steel Containing δ Ferrite." Metals 12, no. 11 (October 24, 2022): 1794. http://dx.doi.org/10.3390/met12111794.

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The early-stage M23C6 morphology at the phase boundary between austenite and δ ferrite grain in Type 304L austenitic stainless steel was investigated with transmission electron microscopy (TEM). The M23C6 has coherency with austenite grains at phase boundary. The phase boundary between the M23C6 and austenite grains has curved appearance. The curved phase boundary might be a faceted interface composed of (111) plane and the other low-index planes on the atomic scale. The M23C6 morphology at the phase boundary was identified to be a complex pyramid-like shape that has {111}, {110} and {100} interfaces. The slight deviation in the angle measured between edges of carbide in the TEM images from that calculated between edges expected from the M23C6 morphology might be attributed to multilayer growth in the interior region of the M23C6 face.

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Song, Young-Gy, Jun-Seok Oh, Baig-Gyu Choi, Chang-Yong Jo, and Je-Hyun Lee. "Effects of Primarily Solidified Dendrite and Thermal Treatments on the M23C6 Precipitation Behavior of High-Chromium White Iron." Metals 11, no. 11 (October 23, 2021): 1690. http://dx.doi.org/10.3390/met11111690.

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The precipitation behavior of M23C6 carbide during thermal treatment of high-Cr white iron with various fractions of primarily solidified dendrite was studied and reviewed. M23C6 precipitation in the primarily solidified dendrite occurred preferentially during conventional heat treatment, whereas it occurred scarcely in the eutectic austenite. The reaction between M7C3 and austenite caused the dissolution of M7C3 into austenite, followed by precipitation of M23C6 along the periphery of eutectic M7C3. Relatively low-temperature thermal treatment (modified heat treatment) led to precipitation of M23C6 particles in the eutectic austenite, which is presumed to be caused by solubility difference depending on temperature.

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4

Redjaïmia, Abdelkrim, and Antonio Manuel Mateo Garcia. "On the M23C6-Carbide in 2205 Duplex Stainless Steel: An Unexpected (M23C6/Austenite)—Eutectoid in the δ-Ferritic Matrix." Metals 11, no. 9 (August 25, 2021): 1340. http://dx.doi.org/10.3390/met11091340.

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This study is focused on isothermal and anisothermal precipitation of M23C6 carbides from the fully ferritic structure of the (γ + δ) austenitic-ferritic duplex stainless steel X2CrNiMo2253, (2205). During isothermal heat treatments, small particles of K-M23C6 carbide precipitates at the δ/δ grain-boundaries. Their formation precedes γ and σ-phases, by acting as highly potential nucleation sites, confirming the undertaken TEM investigations. Furthermore, anisothermal heat treatment leads to the formation of very fine islands dispersed throughout the fully δ-ferritic matrix. TEM characterization of these islands reveals a particular eutectoid, reminiscent of the well-known (γ-σ)—eutectoid, usually encountered in this kind of steel. TEM and electron microdiffraction techniques were used to determine the crystal structure of the eutectoid constituents: γ-Austenite and K-M23C6 carbides. Based on this characterization, orientation relationships between the two latter phases and the ferritic matrix were derived: cube-on-cube, on one hand, between K-M23C6 and γ-Austenite and Kurdjumov-Sachs, on the other hand, between γ-Austenite and the δ-ferritic matrix. Based on these rational orientation relationships and using group theory (symmetry analysis), the morphology and the only one variant number of K-M23C6 in γ-Austenite have been elucidated and explained. Thermodynamic calculations, based on the commercial software ThermoCalq® (Thermo-Calc Software, Stockholm, Sweden), were carried out to explain the K-M23C6 precipitation and its effect on the other decomposition products of the ferritic matrix, namely γ-Austenite and σ-Sigma phase. For this purpose, the mole fraction evolution of K-M23C6 and σ-phase and the mass percent of all components entering in their composition, have been drawn. A geometrical model, based on the corrugated compact layers instead of lattice planes with the conservation of the site density at the interface plane, has been proposed to explain the transition δ-ferrite ⇒ {γ-Austenite ⇔ K-M23C6}.

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5

Oh, Jun-Seok, Young-Gy Song, Baig-Gyu Choi, Chalothorn Bhamornsut, Rujeeporn Nakkuntod, Chang-Yong Jo, and Je-Hyun Lee. "Effect of Dendrite Fraction on the M23C6 Precipitation Behavior and the Mechanical Properties of High Cr White Irons." Metals 11, no. 10 (October 3, 2021): 1576. http://dx.doi.org/10.3390/met11101576.

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High Cr white irons with various fractions of primary dendrite have been prepared through the modification of their chemical composition. Increasing C and Cr contents decreased the primary dendrite fraction. Eutectic solidification occurred with the phase fraction ratio of austenite: M7C3 = 2.76:1. The measured primary dendrite fractions were similar to the calculated results. ThermoCalc calculation successfully predicted fractions of M7C3, austenite, and M23C6. Conventional heat treatment at high temperature caused a destabilization of austenite, releasing it’s solute elements to form M23C6 carbide. Precipitation of M23C6 during destabilization preferentially occurred within primary (austenite) dendrite, however, the precipitation scarcely occurred within austenite in eutectic phase. Thus, M23C6 precipitation by destabilization was relatively easy in alloys with a high fraction of primary dendrite.

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6

Li, Shanlin, Kejian Li, Mengjia Hu, Yao Wu, Zhipeng Cai, and Jiluan Pan. "The Mechanism for HAZ Liquation of Nickel-Based Alloy 617B During Gas Tungsten Arc Welding." Metals 10, no. 1 (January 6, 2020): 94. http://dx.doi.org/10.3390/met10010094.

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The mechanism for HAZ (heat-affected zone) liquation of alloy 617B during gas tungsten arc welding (GTAW) was investigated. Welding thermal simulation work was conducted to investigate the effects of thermal parameters (peak temperature, holding time, and thermal cycle numbers) on M23C6 carbides’ evolutionary behavior in nickel-based alloy 617B. OM (optical microscopy), SEM (scanning electron microscopy), TEM (transmission electron microscopy), and SIMS (secondary ion mass spectrometry) were employed to characterize HAZ carbides. It was found that the constitutional liquation of M23C6 carbides is responsible for HAZ liquation in alloy 617B. Rapid heating meant that solute atoms released from partially dissolved M23C6 carbides did not have enough time to sufficiently diffuse into the matrix, resulting in eutectic reaction M23C6 + γ → liquid in the temperature range from 1250 °C to 1300 °C. In the following cooling process, the liquid phase transformed into γ and M23C6 (or M6C) carbides simultaneously, creating a eutectic microstructure. Subsequent thermal cycles with peak temperature 1100 °C and proper holding time brought about a tempering effect to precipitate fine M23C6 carbides from the Cr supersaturated zone around the eutectic microstructure. Boron was found to be enriched in carbides and was expected to promote HAZ liquation by two mechanisms. No cracking caused by HAZ liquation has been found, indicating that GTAW is a suitable method for joining alloy 617B.

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7

Igarashi, Masaaki, Koji Moriguchi, Seiichi Muneki, Fujio Abe, and Yasuharu Shirai. "Analysis of Creep Deformation Process of Heat Resistant Steels Using Positron Annihilation Lifetime." Materials Science Forum 561-565 (October 2007): 2233–36. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2233.

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Creep deformation mechanism of the steels with a different matrix, α (ferrite), α’ (martensite) and γ (austenite), and precipitates such as MX and M23C6 has been analyzed using positron annihilation lifetime measurement. The positron annihilation lifetime has been found to be a very useful tool for evaluating the characteristic creep damage of the steels with different microstructure and the corresponding microstructural evolution during creep deformation. The creep deformation process of the α steel is heterogeneous, while the α’+M23C6 steel exhibits gradual changes in the creep rate in both transient and acceleration creep regions with the largest off-set strain, implying the homogeneous creep deformation. The α’+M23C6+ MX steel is in between the α and α’+M23C6 steels. The homogeneous creep deformation takes place in the γ steel.

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8

Laigo, Johanne, Franck Tancret, René Le Gall, and Jader Furtado. "EBSD Phase Identification and Modeling of Precipitate Formation in HP Alloys." Advanced Materials Research 15-17 (February 2006): 702–7. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.702.

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Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used as reformer tubes in petrochemical industries. Their composition includes Nb and Ti as strong carbide formers. In the ascast condition, alloys exhibit an austenite matrix with intergranular MC, M23C6 and/or M7C3 eutectic carbides. During exposure at high temperature, phase transformations occur: chromium carbides of M7C3 type transform into the more stable M23C6 type, intragranular M23C6 carbides precipitate, and a silicide, the G-phase (Ni16Nb6Si7), forms due to the instability of MC carbides (NbC). Thermodynamic simulation is of great help for understanding precipitate formation and transformations. Thermo-Calc and Dictra are used to simulate the precipitation of carbides in the austenite matrix during service. However, from an experimental point of view, M23C6 and M7C3 are not easy to distinguish in bulk alloys. Indeed, backscattered scanning electron microscopy does not bring any contrast between the two phases, and energy dispersive spectroscopy (EDS) analysis does not lead to carbon content and consequently to the distinction between M23C6 and M7C3. With transmission electron microscopy (TEM), sample preparation is difficult and the observed area is extremely small. In the present work, HP alloys are investigated by electron backscatter diffraction (EBSD) coupled to EDS. Carbides are identified on the basis of crystal structure, in the bulk, within their microstructural context, and the experimental procedure is both simpler and cheaper than TEM. Precipitates (M23C6, M7C3) could be identified by orientation mapping and single spot analysis.

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9

Chouksey, Yogendra, and Surya D. Yadav. "Influence of alloying elements on the coarsening coefficients of M₂₃C₆ and M₂B precipitates in a 10% Cr Belgorod steel." IOP Conference Series: Materials Science and Engineering 1248, no. 1 (July 1, 2022): 012028. http://dx.doi.org/10.1088/1757-899x/1248/1/012028.

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Abstract A 10% Cr steel designed by ‘Belgorod State University’, has been considered in the present work in order to study the effect of alloying elements on the coarsening characteristics of precipitates. The stepped equilibrium diagram was constructed through the CALPHAD approach, employing the ThermoCalc software. The precipitates observed at the temperature of interest, i.e., 650 °C, were M23C6 (M=Cr, Fe), Laves phase, M2B, NbC and TiN. Amongst all the precipitates, M23C6 has the maximum phase fraction, i.e., 0.022. The magnitude of the coarsening coefficients for all the precipitates other than Laves phase, were observed to be of the order of 10-29 m3/s. In case of Laves phase, it was of the order of 10-31 m3/s. The variation of the coarsening coefficients of M23C6 and M2B, with respect to weight percent of alloying elements has been also investigated. It was observed that, with the increase in the weight percent of Co, Nb and W; the coarsening coefficients of M23C6 and M2B decrease. However, with the increase in weight percent of the V, the coarsening coefficients of M23C6 decrease and M2B increase.

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10

Liu, Yang, Lei Wang, Yu Chen Wang, Hong Yan Liu, Xue Jiao Chen, and Yan Yu. "Effects of Electropulsing Treatment on the Precipitation Behaviour of Grain Boundary Carbides in GH3044 Alloy." Materials Science Forum 654-656 (June 2010): 464–67. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.464.

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The effects of electropulsing treatment on the precipitation behaviour of grain boundary carbides in GH3044 alloy were investigated. The results showed that the initial temperature of precipitation of M23C6 type carbides on grain boundary could be decreased by electropulsing treatment under the condition of high current density of 10.0kA/mm2 with a frequency of 5Hz and pulse width of 15s. The volume percentage of M23C6 type carbide was greatly increased to 274.60% comparing with that of the aging treatment at the same temperature. However, the precipitation of M23C6 type carbide was inhibited by electropulsing treatment under the condition of high frequency of 45Hz with the current density of 2kA/mm2 and pulse width of 15s. The volume percentage of M23C6 type carbide was decreased to 18.81% comparing with that of the aging treatment at the same temperature. It has been found that the diffusion of solute atom in the alloy can be promoted by the electric effect with the electropulsing. As a result, the thermodynamic condition and kinetics of the precipitation of M23C6 type carbide were changed, and both the initial and peak temperatures of precipitation were decreased.

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11

Yoo, Il, Seok-Woo Ko, Jaeyun Kim, and Byoungchul Hwang. "Effect of Precipitates and Cold Working on the Reheat Cracking of STS 347 Austenitic Stainless Steel." Korean Journal of Metals and Materials 60, no. 2 (February 5, 2022): 102–13. http://dx.doi.org/10.3365/kjmm.2022.60.2.102.

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The aim of this study was to investigate the effect of precipitates and cold working on the reheat cracking of STS 347 austenitic stainless steel. Three different heat treatments to form NbC and M23C6 precipitates were applied to the STS 347 austenitic stainless steel and 10% pre-strain was additionally introduced to simulate cold working. The NbC and M23C6 precipitates were examined by SEM and XRD analysis, and creep rupture test was conducted under various temperature and stress conditions. The specimen having intergranular NbC precipitate prior to cold working had enhanced intergranular creep resistance and the tendency to reheat cracking decreased at temperature conditions between 650 oC and 750 oC, compared to the specimens processed by solution treatment or M23C6 formation treatment. This means that for STS 347 that has not been subjected to stabilization treatment, the cold working strain limits required by ASME’s boiler and pressure vessel code should be lowered, or if stress relief treatment is impractical, the stabilization heat treatment should be performed prior to cold working. Although the precipitation of M23C6 is not the major cause of reheat cracking, it should still be considered as a factor that increase the sensitivity of reheat cracking because M23C6 forms mostly at the grain boundary and grows rapidly, adversely affects creep ductility.

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12

Abe, Fujio. "Behavior of Boron in 9Cr Heat Resistant Steel during Heat Treatment and Creep Deformation." Key Engineering Materials 345-346 (August 2007): 569–72. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.569.

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The effect of boron on microstructure evolution and creep deformation behavior has been investigated for a tempered martensitic 9Cr-3W-3Co-0.2V-0.05Nb steel at 650oC. Creep tests were carried out at 650oC for up to about 6 x 104 h. The addition of boron retards the onset of acceleration creep at low stress and long time conditions, which results in lower minimum creep rate and longer time to rupture. The addition of boron also retards the Ostwald ripening of M23C6 carbides near prior austenite grain boundaries (PAGBs) during creep. The retardation of the onset of acceleration creep results from the retardation of the recovery of martensitic microstructure near PAGBs by pinning effects due to fine M23C6 carbides. The main effect due to boron is considered to occupy vacancies near growing M23C6 carbides, which makes it difficult to accommodate local volume change around the growing carbides. This reduces the rate of Ostwald ripening of M23C6 carbides.

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13

Wang, H. C. "A Differential Scanning Calorimetric Study of Carbide Transition in 10Cr Tempered Martensitic Steels." MRS Proceedings 1754 (2015): 37–42. http://dx.doi.org/10.1557/opl.2015.586.

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ABSTRACTThe process and kinetics of carbide precipitation upon tempering of an Fe-10Cr-0.15C (wt.%) alloy fabricated from high-purity components has been studied. Differential scanning calorimetry reveals three exotherms in a temperature range of 100-700°C. Using advanced electron microscopy and Kissinger analysis, the exothermic processes have been interpreted. Cementite precipitated first upon tempering at temperatures as low as 200°C; M7C3 and M23C6 appear at higher temperatures, precipitating at approximately the same time but on different sites (M7C3 within grains and laths and M23C6 on grain and lath boundaries). Subsequently, the more stable M23C6 coarsens at the expense of M7C3, which dissolves. The first exotherm was interpreted as being related to the precipitation of cementite whilst the other two overlapping exotherms were interpreted as relating to the concurrent precipitation and coarsening of M7C3 and M23C6, respectively. In-situ SEM and TEM observation is being conducted in order to obtain a more precise understanding and further validate the interpretation of the DSC results.

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14

Saucedo-Muñoz, Maribel L., Victor M. Lopez-Hirata, Hector J. Dorantes-Rosales, Jose D. Villegas-Cardenas, Diego I. Rivas-Lopez, Manuel Beltran-Zuñiga, Carlos Ferreira-Palma, and Joel Moreno-Palmerin. "Phase Transformations of 5Cr-0.5Mo-0.1C Steel after Heat Treatment and Isothermal Exposure." Metals 12, no. 8 (August 19, 2022): 1378. http://dx.doi.org/10.3390/met12081378.

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This study consists of the experimental and numerical analysis of the phase transformations of 5Cr-0.5Mo.0.1C steel after heat treatment. The microstructure of the as-received steel comprised ferrite and bainite, which is in agreement with the microconstituents predicted by the Calphad-calculated TTT diagram. Calphad-based precipitation calculations show that the cooling stage of normalizing treatment did not cause carbide formation. In contrast, tempering at 700 °C for 15 min promotes the intergranular precipitation of Fe3C, M7C3 and M23C6 carbides, which is consistent with experimental results. Aging at 600 °C for short periods caused the precipitation of both M7C3 and M23C6 carbides; however, M23C6 is the dominant phase after prolonged aging. This is in agreement with experimental results. A rapid decrease in the steel hardness was observed after short aging, which is attributable to bainite transformation. Further reduction in hardness is associated with the diffusion-controlled coarsening of M23C6 carbide.

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15

Gu, Bao Lan, Jian Xin Dong, and Tong Xu. "The Microstructure Stability of Super304H Steel Aging at 750°C." Materials Science Forum 898 (June 2017): 730–34. http://dx.doi.org/10.4028/www.scientific.net/msf.898.730.

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The microstructure stability and the effect of microstructure evolution on the properties of Super304H steel aged at 750°C for different time were investigated. The results showed that the microstructure of the Super304H steel after aging at 750°C consists of primary matrix and large amount of precipitated phases. The main precipitates were Cu-rich phase, MX phase and M23C6 carbides in austenitic matrix during aging. The M23C6 carbides precipitate preferentially at grain boundaries, and then coarsening remarkably with increasing aging time. The MX phase was stable during the whole aging process. The Cu-rich particle is smaller than 10 nm at the initial aging stage, and then coarsen with increasing aging time. The strength and hardness increase obviously at the initial stage due to the interaction of Cu-rich phase, MX phase and M23C6 carbides precipitation strength, in which Cu-rich phase strengthen action is the dominant. Coarsening M23C6 carbides weaken the strength during aging.

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16

Li, Zhenjiang, Pengju Jia, Yujing Liu, and Huiping Qi. "Carbide Precipitation, Dissolution, and Coarsening in G18CrMo2–6 Steel." Metals 9, no. 9 (August 22, 2019): 916. http://dx.doi.org/10.3390/met9090916.

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The precipitation, dissolution, and coarsening of different carbides at 680 °C in G18CrMo2–6 steel was investigated experimentally combined with Jmatpro simulation. The G18CrMo2–6 steel was normalized at 940 °C, followed by tempering at different times at a constant temperature of 680 °C. During the tempering process, there are mainly two kinds of carbide, namely M3C and M23C6. Through characterization of microstructural evolution, thermodynamic calculation, and kinetic simulation, it was observed that during the tempering process, the stable M23C6 carbide was growing, whereas the metastable M3C carbide was disappearing. At the end, the M3C carbide was dissolved and the M23C6 carbide was in equilibrium with the matrix.

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17

Zhao, Hongchang, Xi Han, Mingjia Wang, and Zixi Wang. "Effect of Long-Term Thermal Aging on Microstructure Evolution and Creep Deformation Behavior of a Novel 11Cr-3W-3Co Martensite Ferritic Steel." Materials 15, no. 10 (May 20, 2022): 3659. http://dx.doi.org/10.3390/ma15103659.

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This paper focused on the microstructure evolution under different thermal aging times at 650 °C and its effect on creep behavior in 11Cr-3W-3Co heat-resistant steel. After short-term thermal aging at 650 °C (>750 h), a Laves phase was found in the regions adjacent to the PAG boundaries, martensitic lath boundaries, and M23C6 carbides, and gradually swallowed adjacent M23C6 carbides with the aging time increased. Higher contents of Si and P are good promoters of the nucleation of the Laves phase during long-term aging. In addition, the coarsening behavior of the Laves phase, M23C6, and MX were investigated. As the aging time increases, the coarsening behavior among precipitated phases in the above-mentioned example exhibits remarkable variability, which is discussed in detail in this paper, and the evolution of the subgrain size was also analyzed in detail. The increasing rate of subgrain size is, in general, consistent with that of the M23C6 carbide size. The evolution of dislocation density in different aging times shows an obvious difference, and the decreasing rate of dislocation density is significantly affected by the precipitated phase after long-term aging time. The creep performance of the material decreases significantly as the aging time increases, which is closely related to the coarsening of the precipitates such as M23C6 carbides and subgrain during long-term aging.

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18

Jo, Tae Sun, Gil Su Kim, Young Ik Seo, Woo Seog Ryu, and Young Do Kim. "Microstructure and High Temperature Mechanical Properties of Inconel 617." Materials Science Forum 544-545 (May 2007): 411–14. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.411.

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Inconel 617 is a candidate tube material for high temperature gas-cooled reactors (HTGR). The microstructure and mechanical properties of Inconel 617 were studied after exposure at high temperature of 1050oC. The dominant oxide layer was Cr-oxide. The internal oxide and Crdepleted region were observed below the Cr-oxide layer. The major second phases are M23C6 and M6C types of carbides. The composition of M23C6 and M6C were determined to be Cr21Mo2C6 and Mo3Cr2(Ni,Co)1C, respectively, by EDS. These carbides are coarsened during exposure. M6C carbide is more stable than M23C6 at high temperature. There was not much change in mechanical properties after exposure at 1050oC for 1000 h.

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19

Mineta, S., Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda, and Takayuki Narushima. "Changes in Microstructure of Biomedical Co-Cr-Mo-C Alloys with Solution Treating and Aging." Advanced Materials Research 89-91 (January 2010): 377–82. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.377.

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Microstructural changes occurring in biomedical Co-Cr-Mo alloys with three carbon levels due to solution treatment and aging were investigated. Ingots of Co-Cr-Mo alloys with three different carbon levels were prepared by vacuum furnace melting; their chemical composition was Co-28Cr-6Mo-xC (x = 0.12, 0.25 and 0.35 mass%). Precipitates were electrolytically extracted from as-cast and heat-treated alloys. An M23C6 type carbide and a phase were detected as precipitates in as-cast Co-28Cr-6Mo-0.12C alloy, and an M23C6 type carbide and an  phase (M6C-M12C type carbide) were detected in as-cast Co-28Cr-6Mo-0.25C and Co-28Cr-6Mo-0.35C alloys. Only the M23C6 type carbide was detected during solution treatment. Complete precipitate dissolution occurred in all the three alloys after solution treatment. The holding time required for complete precipitate dissolution increased with increasing carbon content and decreasing solution treatment temperature. Complete precipitate dissolution occurred in the Co-Cr-Mo-C alloys solution treated at 1523 K for 43.2 ks; they were then subjected to aging from 873 to 1473 K for a heating time up to 44.1 ks after complete precipitate dissolution in solution treatment at 1523 K for 43.2 ks. The M23C6 type carbide with a grain size of 0.1–3 m was observed after aging. A time-temperature-precipitation diagram of the M23C6 type carbide formed in the Co-28Cr-6Mo-0.25C alloy was plotted.

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20

Choi, Baig Gyu, In Soo Kim, Doo Hyun Kim, and Chang Yong Jo. "MC Carbide Decomposition during Thermal Exposure of Polycrystalline Ni-Base Superalloys." Solid State Phenomena 124-126 (June 2007): 1505–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1505.

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MC decompositions during thermal exposure have been investigated in three conventional cast Ni-base superalloys, GTD111, IN738LC, and CM247LC. MC decomposition in GTD111 and IN738LC depends on exposure temperature. While MC decomposed into M23C6 at 982°C, η formed from MC after exposure at 927°C and 871°C. Ta and Ti separated from MC during thermal exposure made η phase to form instead of γ'. The decomposition of the MC in CM247LC depends on their morphology and position. Segregation during casting process affected the morphology and composition of MC type carbide in this alloy. Acicular M6C was found near scriptal MC in the dendrite. Blocky MC near γ-γ' eutectic decomposed into M23C6. Both M23C6 and M6C can be found on grain boundary after thermal exposure in CM247LC.

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21

Merda, Agata, Grzegorz Golański, Paweł Wieczorek, and Kamil Staszałek. "The Analysis of the Microstructure of Welded Joints in Steel P5 after Service." Biuletyn Instytutu Spawalnictwa, no. 5 (October 2020): 7–12. http://dx.doi.org/10.17729/ebis.2020.5/1.

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The material subjected to the tests discussed in the article was a section of a welded joint made of bainitic steel P5. The joint subjected to analysis was sampled from a pipe section exposed to the effect of elevated temperature for more than 96 000 hours. The metallurgical tests revealed a relatively low degree of the degradation of the test joint. The microstructure contained retained bainite and precipitates of various morphology. The identification of precipitates revealed the presence of M23C6 and M2C precipitates in the joint. The M23C6 carbides were observed along the boundaries of former austenite grains. The above-named identification of precipitates also revealed the presence of M2C and M23C6 C6 carbides within the grains/laths. The insignificant exhaustion of the joint microstructure might be ascribed to the fact that the joint was subjected to relatively low temperature for a relatively short time.

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22

Li, Zihua, Tingping Hou, Guanghui Wu, Kaiming Wu, and Hengfu Lin. "Thermodynamic Analysis for the Magnetic-Field-Induced Precipitation Behaviours in Steels." Metals 9, no. 8 (August 19, 2019): 909. http://dx.doi.org/10.3390/met9080909.

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Alloy carbide M23C6 plays a significant role in the creep strength of reduced activation steels. Experiments have proven that a magnetic field accelerates the precipitation of M23C6 at intermediate temperature. A scheme that combines first-principle calculations, Weiss molecular field theory and equilibrium software MTDATA is proposed to investigate the thermodynamic features of magnetic-field-induced precipitation. The calculated results reveal that the origin of the magnetic moment is the NaCl-like crystal structure. The magnetic field enhances the exchange coupling and stabilizes the ferromagnetic phase region. The external field influences the Curie temperature, thereby changing the magnitude and position of the maximum magnetic heat capacity, magnetic entropy and enthalpy. The strong magnetic field improves the stability of M23C6, and the theoretical results agree well with the previous experiment. The study provides a theoretical basis for the magnetic-field-induced precipitation behaviours in steels.

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23

Joseph, C., C. Persson, and M. Hörnqvist Colliander. "Precipitation Kinetics and Morphology of Grain Boundary Carbides in Ni-Base Superalloy Haynes 282." Metallurgical and Materials Transactions A 51, no. 12 (October 6, 2020): 6136–41. http://dx.doi.org/10.1007/s11661-020-06019-1.

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AbstractPrecipitation of grain boundary carbides in a mill-annealed Haynes 282 in the temperature range 650 °C to 1120 °C was investigated. The kinetics of M23C6 was significantly faster than that of M6C. With increasing aging temperature, the morphology changes from continuous film to an interconnected brick wall structure and finally to discrete particles. No morphological changes were observed with aging time. Serrated grain boundaries formed during aging around 750 °C. The solvus temperature for both M23C6 and M6C was approximately 1100 °C.

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24

Purzyńska, Hanna, Grzegorz Golański, Michał Kwiecień, and Dariusz Paryż. "IMPACT OF USE ON RELEASE PROCESSES IN AUSTENITIC STEEL TP347HFG." Journal of Metallic Materials 72, no. 4 (March 30, 2021): 22–26. http://dx.doi.org/10.32730/imz.2657-747.20.4.3.

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The article presents an analysis of precipitation processes in heat-resistant TP347HFG steel after 41,000 h of operation at 585°C. Microstructure investigation showed that the use of the tested steel resulted mainly in the precipitation processes occurring at grain boundaries. Identification of the precipitates showed the presence of M23C6 carbides and σ phase particles along boundaries. Single M23C6 carbide particles were revealed also at twin boundaries. Inside austenite grains, apart from large, primary precipitates, finely-dispersed secondary NbX particles (X = C,N) were also observed.

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25

Caballero, F. G., A. García-Junceda, C. Capdevila, and C. García de Andrés. "Precipitation of M23C6 carbides: thermoelectric power measurements." Scripta Materialia 52, no. 6 (March 2005): 501–5. http://dx.doi.org/10.1016/j.scriptamat.2004.11.005.

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26

Rutkowski, Bogdan. "Microstructural Characterisation of Austenitic Heat Resistant Sanicro 25 Steel after Steam Oxidation." Materials 13, no. 15 (July 30, 2020): 3382. http://dx.doi.org/10.3390/ma13153382.

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Microstructural and morphological observations of the surface scale on a high Cr and Ni austenitic heat resistant steel oxidised in water vapour at 700 °C are reported. Analysis of microstructure was carried out by analytical techniques of transmission- and scanning electron microscopy. Investigation of M23C6 nucleated at the interface between matrix and the Z-phase precipitates after exposing to high temperature showed semicoherency between M23C6 and the matrix and no coherency with the Z-phase. Plates developed on the oxide scale surface consist of Cr2O3 crystals separated by amorphous SiO2.

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27

Dudko, Valeriy, Andrey Belyakov, and Rustam Kaibyshev. "Effect of Tempering on Mechanical Properties and Microstructure of a 9% Cr Heat Resistant Steel." Materials Science Forum 706-709 (January 2012): 841–46. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.841.

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Effect of tempering temperature ranged from 400 to 720°C on mechanical properties and microstructure of a P92-type creep resistant steel was investigated. The hardness value of 400 HB, which was obtained after solution treatment, increased to 430 HB with increasing the tempering temperature to 525°С. Further increase in the tempering temperature resulted in gradual decrease in hardness, which approached a level of about 220 HB after tempering at 720°С. The equiaxed particles of MX-type carbonitrides with a size of about 30 nm were precipitated randomly after tempering under all conditions. At temperatures below 525°C, the tempered martensite lath structure (TMLS) was characterized by a random distribution of fine M3C-type carbides and MX-type carbonitrides. The precipitation of M23C6 was observed after tempering at T ≥ 525°C. At 525°C, the M23C6 carbides appeared as thin films on high-angle boundaries (HAB), while M23C6 particles having almost equiaxed shape and located on various boundaries including low-angle lath boundaries precipitate at higher temperatures.

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28

Xie, Wencai, Dong Wu, and Shanping Lu. "Effects of boron addition on the microstructure and creep properties of a Ni-Fe-based superalloy weld metal alloy." Materials Research Express 9, no. 2 (February 1, 2022): 026522. http://dx.doi.org/10.1088/2053-1591/ac5078.

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Abstract The role of boron in the creep properties and grain boundary characteristics in a new Ni-Fe-based weld metal suitable for advanced ultra-supercritical (A-USC) coal-fired power plant applications has been investigated. Ni-Fe-based filler wires without boron and boron-doped (50 ppm wt% boron) were prepared for this study. Boron-doped weld metals exhibited longer rupture lives and lower steady creep rates during the creep rupture tests at 750 °C / 380 MPa and 750 °C / 210 MPa. This study explains the improvement mechanism of boron on creep resistance from the perspective of the effect of boron on M23C6. Boron increased the nucleation rate of M23C6 and participated in the formation of M23(C, B)6 type boron-carbides. After creep deformation, boron still existed stably in the M23(C, B)6. The higher density of discrete M23C6 particles due to boron addition could restrain grain boundary crack propagation and grain boundary sliding, and thereby improve the creep fracture resistance of the GH984G weld metal at 750 °C / (380/ 210 MPa).

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29

He, Cheng, Bao Liang Shi, Wen Sheng Li, Jian Ping Zhao, Kai Xu, Yang Liu, Ai Ren, and Yan Li. "Influence of Service Time on the Microstructure and High Temperature Mechanical Properties of T23 Boiler Tube." Materials Science Forum 898 (June 2017): 711–18. http://dx.doi.org/10.4028/www.scientific.net/msf.898.711.

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The influence of long time service on the microstructure and high temperature mechanical properties of T23 steel was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile testing machine. Results showed that lathy bainite ferrite disappears with the increasing service time, both the size and number of the carbides increases, and M23C6 carbides transform into M6C carbides rich in W element. The service process also has a significant influence on the recovery. Sub-grains were found at the grain boundaries with little dislocations in the matrix after 27448 h service time. After running for 27448 h the microstructure degradation of T23 steel is serious. High temperature tensile properties of T23 are closely related to the alloy aging degree. The reasons for the decrease of high temperature mechanical properties after long time service included microstructure degradations such as the increase of both the size and quantity of M23C6 carbides, the transformation of M23C6 to M6C, the desolution of Cr,W,and Mo elements, the decrease of the dislocation density and the occurrence of the sub-grains.

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30

Mineta, Shingo, Alfirano, Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda, and Takayuki Narushima. "Phase and Morphology of Carbides in ASTM F75 Co-Cr-Mo-C Alloys Formed at 1473 to 1623 K." Materials Science Forum 654-656 (June 2010): 2176–79. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2176.

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The phase and morphology of precipitates in heat-treated Co-28Cr-6Mo-xC (x = 0.12, 0.15, 0.25, and 0.35mass%) alloys were investigated. The as-cast alloys were solution-treated in the temperature range of 1473 to 1623 K for 0 to 43.2 ks. Complete precipitate dissolution was observed in all four alloys, each of which had different carbon contents. The holding time for complete dissolution was greater for alloys with greater carbon content. The curve representing the boundary between the complete- and incomplete-dissolution conditions for each alloy is C shaped. Under the incomplete precipitate dissolution conditions of the Co-28Cr-6Mo-0.25C alloy, an M23C6 type carbide and a π-phase (M2T3X type carbide with β-Mn structure) were observed at 1548 to 1623 K, and starlike precipitates with a stripe pattern and with a dense appearance were both observed; the former comprised the M23C6 type carbide + γ-phase, and the latter was the π-phase. In contrast, only a blocky-dense M23C6 type carbide was observed at 1473 to 1523 K.

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31

Alfirano, Shingo Mineta, Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda, and Takayuki Narushima. "Heat Treatment of ASTM F75 Co-Cr-Mo-C-Si-Mn Alloys." Materials Science Forum 654-656 (June 2010): 2180–83. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2180.

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In this study, the carbide dissolution and formation of biomedical Co-28Cr-6Mo-0.25C-1Si (1Si) and Co-28Cr-6Mo-0.25C-1Mn (1Mn) alloys occurring during solution treatment and aging were investigated. The addition of Si or Mn markedly affected the behavior of precipitates during heat treatment. The alloy with added Si required a longer solution treatment time for complete precipitate dissolution as compared to the alloy with added Mn. Blocky M23C6-type carbide was observed during solution treatment at 1448–1523 K. Starlike precipitates were observed in the 1Si and 1Mn alloys at 1523–1548 K and 1523 K, respectively. The starlike precipitates exhibited two types of morphologies: dense and stripe patterned. The starlike precipitates with dense and stripe-patterned appearances were a -phase and M23C6¬-type carbide + metallic -phase, respectively. An M23C6-type carbide and an -phase were formed during the aging of both the 1Si and the 1Mn alloys. In addition, an intermetallic -phase was detected during the aging of the 1Si alloy at 1373 K.

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32

Yu, Qiu Ying, Zhi Shen, Mai Cang Zhang, Guo Qing Jia, and Xi Shan Xie. "Long-Time Thermal Structural Stability Study on NiCr20TiAl Alloy." Advanced Materials Research 399-401 (November 2011): 71–75. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.71.

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The coarsening kinetics of main strengthening phase γ′ and the growth behavior of grain boundary carbides have been investigated on NiCr20TiAl alloy aged at 550~750°C for 200~10,000h. The precipitates of NiCr20TiAl alloy at standard heat treatment condition are γ′, M7C3, M23C6 and MC. The coarsening of γ′ precipitates proceeds by Ostwald ripening controlled by volume diffusion in the alloy. Grain boundary carbides M23C6 and M7C3 increase with ageing times and temperatures. The morphologies of precipitates after long-time ageing almost remain the same as that at standard heat treatment condition except 750°C.

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33

Shi, Feng, Yang Qi, and Chun Ming Liu. "Effects of Mn on the Precipitation Behaviors in High-Nitrogen Austenitic Stainless Steels." Advanced Materials Research 194-196 (February 2011): 32–37. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.32.

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Precipitation behaviors of Fe-18Cr-12Mn-0.48N and Fe-18Cr-18Mn-0.43N high-nitrogen austenitic stainless steels isothermally aged at 800°C were investigated by using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that precipitation both display discontinuous cellular way and the major precipitates are both M2N phases accompanied by scattered M23C6 phases at grain boundary in the experimental steels. Increment of Mn content can not change the precipitation way and precipitation type. Increment of Mn content makes M2N precipitates obviously increase and increment of Mn and C contents makes M23C6 precipitates increase.

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34

Ning, Angang, Stephen Yue, Rui Gao, Lingxia Li, and Hanjie Guo. "Influence of Tempering Time on the Behavior of Large Carbides’ Coarsening in AISI H13 Steel." Metals 9, no. 12 (November 29, 2019): 1283. http://dx.doi.org/10.3390/met9121283.

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The mechanical properties, microstructures and precipitation behaviors in AISI (American Iron and Steel Institute) H13 steel tempered at 863 K for 0.5, 2, 4, 10 and 20 h were investigated. The values for H13 tempered for 2–4 h resulted in die steel that reached the desired properties as specified in NADCA (North American Die Casting Association) #207-2016. The cubic Ostwald ripening model was applied to simulate the coarsening of the large carbides, which were mainly M23C6 and M3C, as determined from FactSage predictions as well as measurements with transmission electron microscopy (TEM). TEM revealed that the equivalent circle radius (ECR) decreased during 0.5–2 h, because of the nucleation of many new precipitates. According to the Ashby-Orowan modified precipitation strengthening model, this decrease in ECR leads to an increase in the contribution of precipitates to yield strength. Between 2 and 4 h tempering, the ECR of large carbides increases sharply but then increases asymptotically from 4 to 20 h, which obeys the calculated Ostwald ripening rate for cementite and M23C6 in H13 after 863 K tempering. This observation for the Ostwald ripening of M23C6 is in agreement with experimental data for other steels in the literature.

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35

Golański, Grzegorz, Cezary Kolan, and Jaonna Kępa. "Changes in Microstructure of GX12CrMoVNbn9-1 Cast Steel after Low Cycle Fatigue." Solid State Phenomena 197 (February 2013): 47–52. http://dx.doi.org/10.4028/www.scientific.net/ssp.197.47.

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The paper presents the influence of low cycle fatigue (LCF) on the changes in microstructure of GX12CrMoVNbN9-1 cast steel after the 1040°C/12h/oil + 760°C/12h/air + 750°C/8h/furnace heat treatment. The examined cast steel was subjected to LCF at room temperature and at 550°C under the conditions of controlled total strain. It was observed that fatigue life of the cast steel decreased with increasing temperature. Cyclic softening was noticed at all temperatures. TEM quantitative characterization of the microstructure after LCF was carried out using: mean diameter of subgrains, density of dislocation and mean diameter of M23C6 carbides. For the mean diameters of subgrains and M23C6 carbides parameters, the histograms were made using STATISTICA 9 software. The research of quantitative parameters of the microstructure was carried out using AnaliSIS programs. Performed research of the quantitative parameters of microstructure has shown that the decrease in fatigue life with the temperature rise and cyclic softening of the cast steel after LCF are related to an increase in the lath width, the change from lath structure to cell/equaixed substructure, a decrease in dislocation density by the recovery process and a growth of M23C6 carbides.

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36

Dudova, Nadezhda, and Rustam Kaibyshev. "Effect of Boron on Microstructure and Impact Toughness of a 10%Cr Martensitic Steel." Materials Science Forum 706-709 (January 2012): 847–52. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.847.

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It was shown that in a 10% Cr martensitic steel enriched by boron this element tends to segregate within M23C6 carbides having the film-like shape and precipitated on the boundaries of prior austenite grains (PAG), mainly. It leads to a low value of Charpy V-notch impact toughness of 6 J/cm2. These carbides are highly resistant against the spheroidizing. Only the tempering at 770°C leads to the final formation of M23C6 carbides having the equiaxed shape. Concurrently, this tempering strongly decreases boron segregation. As a result, the 10% Cr martensitic steel exhibits a high value of Charpy V-notch impact toughness of 260 J/cm2.

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37

Qin, X. Z., Jian Ting Guo, C. Yuan, Jie Shan Hou, and Heng Qiang Ye. "Degeneration of Primary MC Carbide in a Cast Ni-Base Superalloy." Materials Science Forum 546-549 (May 2007): 1301–4. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1301.

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During long-term thermal exposure, the degeneration of primary MC carbide is a diffusion-controlled process. With the element exchange between the primary MC carbide and the γ matrix, three MC degeneration reactions, that is, γ + MC → γ' + M23C6 (Reaction I), MC + γ →η+ M23C6 (Reaction II) and MC + γ →η+ M6C (Reaction III), sequentially operates. Of them Reaction III has never been reported in the previous references and is kinetically most difficulty. It is also shown that the grain boundary MC decomposes much more rapidly than the grain interior MC and that Reaction III is not as often seen at the grain boundary as in the grain interior.

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38

Voice, W. E., and R. G. Faulkner. "The discontinuous precipitation of M23C6 in Nimonic 80A." Journal of Materials Science 22, no. 12 (December 1987): 4221–32. http://dx.doi.org/10.1007/bf01132012.

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39

Ohnishi, Y., Atsushi Yamamoto, Harushige Tsubakino, Mititaka Terasawa, and Shigeo Nakahigashi. "Effect of Cold-Rolling on Precipitation Phenomena in 316L Austenitic Stainless Steel." Advanced Materials Research 26-28 (October 2007): 1287–90. http://dx.doi.org/10.4028/www.scientific.net/amr.26-28.1287.

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Precipitation phenomena in an austenitic stainless steel, SUS316L cold-rolled with various reduction rates were studied by transmission electron microscopy and synchrotron radiation diffractmetry. After the aging at 573 K for 15000 h, two of precipitates were observed, which were identified as M7C3 and M23C6 by SR diffraction and electro diffraction measurements. The precipitates M7C3 were formed at both innergranular and grain boundary, while the precipitate M23C6 was formed at innergranular. The precipitation was promoted with increasing cold rolling reduction. Also segregation of phosphorous was detected along grain boundaries. Besides, the residual stresses were measured with side inclination method using a synchrotron radiation facility, SPring-8. The residual stresses were increased with increasing the cold rolling reduction rate.

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40

Li, Yan Mei, Shu Zhan Zhang, Zai Wei Jiang, Sheng Yu, Qi Bin Ye, Meng Qi Yang, and Yan Hong Xi. "Effect of Tempering Time on Microstructure and Mechanical Properties of SA738 Gr.B Steel." Materials Science Forum 1016 (January 2021): 1739–46. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1739.

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The effect of tempering time on the microstructure and mechanical properties of SA738 Gr.B nuclear power steel was studied using SEM, TEM and thermodynamic software, and its precipitation and microstructure evolution during tempering were clarified. The results showed that SA738 Gr.B nuclear power steel has better comprehensive mechanical properties after tempering at 650 °C for 1h. With the extension of the tempering time, M3C transformed into M23C6 with increasing size, which affected the yield strength and impact energy. When the tempering time is 8h ~ 10h, due to the transformation of M3C to M23C6, the composition of matrix around the carbide changed, causing the temperature of Ac1 dropped, forming twin-martensite which deteriorated the impact toughness of the steel.

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41

Cheng, Shi Chang, Zheng Dong Liu, Hang Sheng Bao, and Jiing Zhong Wang. "Investigation of Bar-Like Carbides in HR3C Boiler Steel." Materials Science Forum 638-642 (January 2010): 3105–10. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3105.

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After the heat treatment at 1200 oC 30 minutes followed by water cooling and 700 oC 4 hours for HR3C (S31042) boiler steel, the bar-like carbides precipitate in grain boundaries and within grains. It was found that the bar-like carbides nucleate in the grain boundaries and grew into grains in a parallel manner. With the help of TEM, the carbides were characterized to be M23C6, with a length of about 6μm and width of 0.6-0.8μm. Through observing crept specimens after testing at 700 oC, it was found that fine and dispersed MX (about 20nm) as well as dislocation walls exist inside grains, except bar-like and granular M23C6 carbide.

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42

Yao, Zhi-Hao, Ya-Ting Ruan, Jian-Xin Dong, Qiu-Ying Yu, Shi-Qing Zhang, and Xi Chen. "Study on Gamma Prime and Carbides of Alloy A286 by Traditional Thermodynamic Calculation." High Temperature Materials and Processes 37, no. 5 (April 25, 2018): 495–507. http://dx.doi.org/10.1515/htmp-2016-0179.

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AbstractEquilibrium phases in alloy A286 and the influence of element contents on gamma prime (γ′) and carbides were studied by Thermo-Calc calculation. The phase equilibria, solidification behavior, and precipitation behavior of equilibrium phases were investigated. In the results, Al is considered as the critical element for γ′ phase control, and C is the vital element for the regulation of MC and M23C6 phases. The influence extents of different elements on the transition temperature and the maximum content of γ′ phase, MC phases, and M23C6 phases are determined in order as Al>Ti>Cr>Mo, C>Ti>Ni>Cr>Mo, and C>Ni>Cr>Mo, respectively.

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43

Sroka, Marek, Adam Zieliński, Grzegorz Golański, and Marek Kremzer. "The Influence of Long-term Ageing on the Microstructure of Sanicro 25 Steel." MATEC Web of Conferences 253 (2019): 03004. http://dx.doi.org/10.1051/matecconf/201925303004.

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Sanicro 25 (22Cr25NiWCoCu) is a newly developed austenitic stainless steel used in the boiler pressure superheaters and reheaters with ultra-supercritical high-efficient parameters. The paper presents the results of microstructure testing and secondary phase separation processes after 20,000 h ageing at 700 and 750 °C. In the initial stage of ageing, the precipitation of numerous very small M23C6 chromium carbides and Laves phase were observed. The long-term ageing related to temperature revealed the existence of secondary phases: M23C6, MX, NbCrN, Laves phase and σ phase. The test results presented in the paper are part of the developed material characteristics to be used for predicting the service life of the material of components operated under creep conditions.

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44

Jandová, Dagmar, Josef Kasl, and Eva Chvostová. "Microstructure of CB2 Steel before and after Long-Term Creep Tests." Materials Science Forum 782 (April 2014): 311–18. http://dx.doi.org/10.4028/www.scientific.net/msf.782.311.

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A pilot 4t valve made of CB2 steel was produced in the frame of COST Action 522. Specimens for long-term creep tests were taken from positions with a wall thickness of 130 mm and 85 mm. Creep testing was carried out at 650°C and a stress range from 50 MPa to 120 MPa. The longest times to rupture of specimens in individual positions were 67,857 h and 82,649 h respectively. Ruptured samples underwent fractographic and microstructural analyses. Quantitative evaluation of substructure was performed using SEM and TEM. Microstructure consisted of tempered martensite with primary boron and niobium nitrides and secondary particles of M23C6 carbide, Laves phase and vanadium nitride. During creep tests coarsening of Laves phase occurred and new particles nucleated on the site of M23C6 carbides, NbN or BN nitrides. Significant increase in volume fraction of Laves phase was detected in specimens ruptured up to 20,000 hours in comparison to as received conditions; any further increase was found out after longer creep exposures. Concerning to M23C6 carbides any important changes were found out in their size and distribution. Density of fine MX nitride was higher after creep tests than in as received conditions with the exception of two longest creep exposures. Several Z-phase particles were also identified after these two exposures.

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45

Golański, Grzegorz, Adam Zieliński, Marek Sroka, and Jacek Słania. "The Effect of Service on Microstructure and Mechanical Properties of HR3C Heat-Resistant Austenitic Stainless Steel." Materials 13, no. 6 (March 13, 2020): 1297. http://dx.doi.org/10.3390/ma13061297.

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The physical metallurgical tests were performed on the test samples made of HR3C steel, taken from a section of a pipeline in the as-received condition and after approximately 26,000 h of service at 550 °C. In the as-received condition, the test material had austenitic microstructure with numerous large primary Z-phase precipitates inside the grains. The service of the test steel mainly contributed to the precipitation processes inside the grains and at the grain boundaries. After service, the following precipitates were identified in the microstructure of the test steel: Z-phase (NbCrN) and M23C6 carbides. The Z-phase precipitates were observed inside the grains, whereas M23C6 carbides - at the boundaries where they formed the so-called continuous grid. The service of the test steel contributed to the growth of the strength properties, determined both at room and elevated temperature (550, 600 °C), compared to the as-received condition. Moreover, the creep properties of HR3C steel after service were higher than those of the material in the as-received condition. The increase in the strength properties and creep resistance was connected with the growth of strengthening of the test steel by the precipitation of Z-phase and M23C6 carbides.

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46

Yu, Hong Yao, Jian Xin Dong, and Xi Shan Xie. "650°C Long-Term Structure Stability Study on 18Cr-9Ni-3CuNbN Heat-Resistant Steel." Materials Science Forum 654-656 (June 2010): 118–21. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.118.

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The Cu-containing austenitic heat-resistant steel 18Cr-9Ni-3CuNbN has been widely used as superheater and reheater tube material for modern ultra-super-critical (USC) power plants in the world. High temperature structure stability is considered to be an important factor for long-term service. Long-term aging at 650°C for this steel was conducted from 100 to 10,000hours. Effect of aging time on microstructure was studied by means of SEM, TEM and 3DAP (three dimensional atom probe). Micro-hardness tests were carried out after aging at 650°C for different times to be considered as a representative of strength. Experimental results show that Cu-rich phase, MX and M23C6 are major strengthening precipitates in this steel. With on increasing of aging time, fine nano-size Cu-rich phase particles precipitate in the grains and its size is in the range of several nanometers to 35nm till 10,000h at 650°C. The fraction of MX also increases with aging time and its average size is about 100nm till 10,000h. Carbide M23C6 mainly precipitates at grain boundaries and coarsens quickly. Investigation results show that the most important strengthening effect for 18Cr-9Ni-3CuNbN steel is contributed by Cu-rich phase and MX in the grains and M23C6 carbide at the grain boundaries.

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47

Rakoczy, Łukasz, Bogdan Rutkowski, Małgorzata Grudzień-Rakoczy, Rafał Cygan, Wiktoria Ratuszek, and Anna Zielińska-Lipiec. "Analysis of γ′ Precipitates, Carbides and Nano-Borides in Heat-Treated Ni-Based Superalloy Using SEM, STEM-EDX, and HRSTEM." Materials 13, no. 19 (October 8, 2020): 4452. http://dx.doi.org/10.3390/ma13194452.

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The microstructure of a René 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 °C-2h) and aged (900 °C-8h). The γ matrix is mainly strengthened by the ordered L12 γ′ phase, with the mean γ/γ′ misfit, δ, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary γ′ precipitates. At the interface of the matrix with secondary γ′ precipitates, nano M5B3 borides are present. In the interdendritic spaces additionally primary γ′ precipitates, MC and nano M23C6 carbides were detected. The γ′ precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of γ′-formers occurs in coarse γ′ surrounding MC carbides. Borides M5B3 contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate’s morphology. The nano M23C6 carbides enriched in Cr have been formed as a consequence of phase transformation MC + γ → M23C6 + γ′ during the ageing treatment.

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48

Abe, Fujio, H. Semba, and T. Sakuraya. "Effect of Boron on Microstructure and Creep Deformation Behavior of Tempered Martensitic 9Cr Steel." Materials Science Forum 539-543 (March 2007): 2982–87. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2982.

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The effect of boron on microstructure and creep deformation behavior has been investigated for a tempered martensitic 9Cr-3WVNb steel with emphasis on the role of boron free from boron nitrides. Creep tests were carried out at 650oC for up to about 3 x 104 h, using specimens of 10 mm in gauge diameter and 50 mm in gauge length. The addition of boron in combination with no nitrogen addition effectively reduces the coarsening rate of M23C6 carbides by an enrichment of boron in M23C6 particles in the vicinity of prior austenite grain boundaries during creep at 650oC. This stabilizes martensitic microstructure during creep and retards the onset of acceleration creep, resulting in a decrease in minimum creep rate and an increase in creep life. Excess addition of boron and nitrogen causes the formation of boron nitrides during normalizing at 1050-1150oC, which reduces dissolved boron and nitrogen. The dissolved boron enriches in M23C6 carbides, while the dissolved nitrogen causes the precipitation of fine MX carbonitrides. The variation of creep rates in transient region and of the onset time of acceleration creep with various combinations of boron and nitrogen contents can be explained by the dissolved boron and nitrogen concentrations after normalizing into account.

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Liu, Mu Tong, Ping Zhong, Wei Sheng, and Zhen Ye Zhao. "Optimized Design of Ultra-High Strength Stainless Steel Based on Thermo-Calc Calculation." Materials Science Forum 993 (May 2020): 585–91. http://dx.doi.org/10.4028/www.scientific.net/msf.993.585.

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The thermodynamic calculation software Thermo-Calc was used to study the influences of alloy elements Cr, Co, and Mo on the precipitated phases of a S280 ultrahigh strength stainless steel at the temperatures ranging from 400 °C to 1200 °C. The results showed that the precipitated phases in the steel were mainly composed of M23C6 carbide, M6C carbide, intermetallic compound of Laves phase and σ phase. The temperature and the content change of alloying elements Cr, Co and Mo have little effect on the precipitation of M23C6 carbide, while have great effect on the precipitation of Laves phase and σ phase. By lowering the element content and adjusting the heat treatment temperature, the precipitation of σ phase in the alloy can be reduced．According to the results of thermodynamic simulation, after optimizing the chemical composition, the Ф300mm bar was trial-produced. The chemical composition, microstructure and mechanical properties of the alloy were analyzed and tested. The results show that, after tempering at 550 °C, the main precipitated phases in the S280 alloy were M23C6 carbide and intermetallic compound of Laves phase. The characterized nano-precipitates have good agreement with simulation results. The optimized design of S280 steel reached a tensile strength over 1930 MPa and a fracture toughness of 90 MPa•m1/2.

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50

Xie, Yixin, Xiaonong Cheng, Jiabo Wei, and Rui Luo. "Characterization of Carbide Precipitation during Tempering for Quenched Dievar Steel." Materials 15, no. 18 (September 16, 2022): 6448. http://dx.doi.org/10.3390/ma15186448.

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Carbide precipitation and coarsening are investigated for quenched Dievar steel during tempering. Lath/lenticular martensite, retained austenite, lower bainite, auto-tempered, and larger spherical carbides are all observed in the as-quenched condition. The carbide precipitation sequence on tempering is ascertained to be: M8C7 + cementite → M8C7 + M2C + M7C3 → M8C7 + M7C3 + M23C6 → M8C7 + M7C3 + M23C6 + M6C; carbides become coarser on tempering, and the sizes for inter-lath carbides increase noticeably with increasing tempering temperatures due to the faster grain boundary diffusion, whereas the sizes for intra-lath carbides remain nearly constant. The rate of coarsening for carbides by tempering at 650 °C is much higher than those by tempering at 550 °C and 600 °C, due to the faster diffusion of alloying elements at higher temperatures.

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Journal articles on the topic 'M23C6'

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