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Soo Woo Nam - One of the best experts on this subject based on the ideXlab platform.
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correlation between the Carbide morphology and cavity nucleation in an austenitic stainless steels under creep fatigue
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Ki Jae Kim, Hu Hong, K S Min, Soo Woo NamAbstract:It is well known that grain boundary cavitation at Carbides is one of the detrimental damaging processes for the degradation of austenitic stainless steels that reduces the creep-fatigue life at high temperatures. In the case of the 316 and 304 austenitic stainless steels, it is found that grain boundary is considerably serrated with the modified heat treatments to the change of Carbide morphology from triangular to planar shape. And it is found that the interfacial mismatch between the neighboring matrix and modified planar Carbides has been reduced to have less incoherency than that between the neighboring matrix and triangular Carbides, so that the creep-fatigue resistance has been remarkably increased. These results imply that the modified Carbides, whose interface energy is lower, have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life. Therefore, it is suggested that the cavity nucleation factor is regarded as the material constant related with the Carbide characteristics.
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improvement of creep fatigue life by the modification of Carbide characteristics through grain boundary serration in an aisi 304 stainless steel
Journal of Materials Science, 2003Co-Authors: Hyunuk Hong, Soo Woo NamAbstract:The modification of Carbide characteristics through grain boundary serration and its subsequent effect on the creep-fatigue property at 873 K have been investigated, using an AISI 304 stainless steel. It was found that the grain boundaries are considerably serrated when a specimen is furnace-cooled. The grain boundary serration leads to a change in the Carbide characteristics as well as grain boundary configuration, i.e., morphology of Carbide from an acute triangular to a planar form and a lowered density. Additionally, an array of Carbide particles is changed from a consistent to zigzag pattern, in terms of their preference to one grain to share the coherency. Planar Carbides on serrated grain boundaries have a lower interfacial energy than that of triangular Carbides on straight grain boundaries. It is suggested that the modification of Carbide characteristics through the grain boundary serration has a remarkable influence on the improvement of creep-fatigue resistance.
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the occurrence of grain boundary serration and its effect on the m23c6 Carbide characteristics in an aisi 316 stainless steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002Co-Authors: Hyunuk Hong, Soo Woo NamAbstract:Abstract M23C6 precipitation behaviors at the grain boundaries have been systematically investigated in an AISI 316 stainless steel. It is found that the grain boundary serration occurs at the early stage of aging treatment, before the M23C6 Carbides precipitate. The occurrence of grain boundary serration is directly dependent on heat treatment condition, which is responsible for Carbide characteristics. Planar Carbides (low density) are observed at the serrated grain boundaries while triangular Carbides (high density) are observed at the flat grain boundaries. Additionally, grain boundary serration leads to the development of an array of Carbide particles. Some of these Carbide particles are in parallel orientation with one grain and some with the other grain constituting the boundary. High-resolution transmission electron microscope (HRTEM) investigations reveal the interfacial plane of planar Carbide formed at the serrated grain boundary to be (11 1 ). These Carbides probably possess low interfacial energy.
Hyunuk Hong - One of the best experts on this subject based on the ideXlab platform.
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improvement of creep fatigue life by the modification of Carbide characteristics through grain boundary serration in an aisi 304 stainless steel
Journal of Materials Science, 2003Co-Authors: Hyunuk Hong, Soo Woo NamAbstract:The modification of Carbide characteristics through grain boundary serration and its subsequent effect on the creep-fatigue property at 873 K have been investigated, using an AISI 304 stainless steel. It was found that the grain boundaries are considerably serrated when a specimen is furnace-cooled. The grain boundary serration leads to a change in the Carbide characteristics as well as grain boundary configuration, i.e., morphology of Carbide from an acute triangular to a planar form and a lowered density. Additionally, an array of Carbide particles is changed from a consistent to zigzag pattern, in terms of their preference to one grain to share the coherency. Planar Carbides on serrated grain boundaries have a lower interfacial energy than that of triangular Carbides on straight grain boundaries. It is suggested that the modification of Carbide characteristics through the grain boundary serration has a remarkable influence on the improvement of creep-fatigue resistance.
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the occurrence of grain boundary serration and its effect on the m23c6 Carbide characteristics in an aisi 316 stainless steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002Co-Authors: Hyunuk Hong, Soo Woo NamAbstract:Abstract M23C6 precipitation behaviors at the grain boundaries have been systematically investigated in an AISI 316 stainless steel. It is found that the grain boundary serration occurs at the early stage of aging treatment, before the M23C6 Carbides precipitate. The occurrence of grain boundary serration is directly dependent on heat treatment condition, which is responsible for Carbide characteristics. Planar Carbides (low density) are observed at the serrated grain boundaries while triangular Carbides (high density) are observed at the flat grain boundaries. Additionally, grain boundary serration leads to the development of an array of Carbide particles. Some of these Carbide particles are in parallel orientation with one grain and some with the other grain constituting the boundary. High-resolution transmission electron microscope (HRTEM) investigations reveal the interfacial plane of planar Carbide formed at the serrated grain boundary to be (11 1 ). These Carbides probably possess low interfacial energy.
Vivekanand Kain - One of the best experts on this subject based on the ideXlab platform.
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influence of tempering treatment on microstructure and pitting corrosion of 13 wt cr martensitic stainless steel
Corrosion Science, 2018Co-Authors: Sunil Kumar Bonagani, Vishwanadh Bathula, Vivekanand KainAbstract:Abstract Tempering of 13 wt.% Cr martensitic stainless steel resulted in nano-sized M3C Carbides at 300 °C, nano-sized Cr-rich M23C6 Carbides at 550 °C and sub-micron sized Cr-rich M23C6 Carbides at 700 °C. Austenitization resulted in lath martensite with undissolved M23C6 Carbides. Pitting resistance for tempered condition was lower than the austenitized condition with least resistance at 550 °C. The observation was attributed to the presence of a Fe-rich surface film and massive Carbide precipitation with a Cr depletion zone of 7–9 nm at Carbide interface for 550 °C tempered condition as opposed to a Cr-enriched passive film for the austenitized condition.
Oskar Paris - One of the best experts on this subject based on the ideXlab platform.
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influence of cr23c6 Carbides on dynamic recrystallization in hot deformed nimonic 80a alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: Baohui Tian, Christoph Lind, Oskar ParisAbstract:Abstract Dynamic recrystallization (DRX) in hot deformed Nimonic 80a alloys was investigated with and without the presence of Cr 23 C 6 Carbides within grains. Average Carbide sizes and dislocation configurations were investigated by transmission electron microscopy, and Carbide volume fractions were estimated from small-angle X-ray scattering. A drastic decrease of DRX due to the presence of bulk Carbides is found, depending on their size and volume fraction. This can be correlated to modifications of dislocation distributions due to the interactions between Carbides and dislocations.
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local microstructure and its influence on precipitation behavior in hot deformed nimonic 80a
Acta Materialia, 2003Co-Authors: Baohui Tian, Christoph Lind, Gerald A Zickler, Oskar ParisAbstract:Abstract The influence of local microstructure on the kinetics of heterogeneous Carbide precipitation was investigated in hot deformed, commercial nickel-based superalloys Nimonic 80a. The as-deformed alloys were aged at 1073 K for different times, and precipitation characteristics were examined by transmission electron microscopy and small-angle neutron scattering. M 23 C 6 precipitates were found to nucleate at grain boundaries, but in particular also on dislocation lines and boundaries of subgrains. In the early stages of ageing, the kinetics of Carbide precipitation is enhanced and the average Carbide size is smaller as a result of deformation. An influence of the degree of recrystallization on overall Carbide kinetics is also found, which is attributed to differences in the amount of bulk Carbides as compared to Carbides at grain boundaries. In contrast to the behavior of Carbides, the kinetics of the homogeneously distributed γ′ precipitates is not influenced by prior deformation.
Pei Wang - One of the best experts on this subject based on the ideXlab platform.
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influence of the decomposition behavior of retained austenite during tempering on the mechanical properties of 2 25cr 1mo 0 25 v steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Zhonghua Jiang, Pei WangAbstract:Abstract The as-quenched microstructure of 2.25Cr-1Mo-0.25 V steel heavy forgings is granular bainite, which is composed of bainitic ferrite and blocky islands of martensite and retained austenite (RA). In this study, the characteristics of RA decomposition and its effects on the mechanical properties of the steel are investigated. The results show that RA decomposes into a cluster of coarse M23C6 Carbides and ferrite during standard tempering at 700 °C. These coarse Carbides decorate the boundary of the cluster, thus deteriorating the impact toughness of the steel. Accordingly, the size and distribution of these Carbides are tentatively modified by introducing pre-tempering at different temperatures ranging from 180° to 650°C before the standard tempering at 700 °C. This is because during pre-tempering, RA first decomposes into various transitional microstructures such as martensite, bainite or pearlite, which further transform into M23C6 Carbide clusters during the subsequent 700 °C tempering. The experimental results show that 455 °C is the optimal pre-tempering temperature to improve the impact toughness of the steel after the 700 °C tempering. Microstructural observations reveal that during the 455 °C pre-tempering step, the RA completely decomposes into bainite consisting of fine bainitic packets and a high density of M3C Carbides, which provide additional nucleation sites for M23C6 Carbides inside the Carbide clusters during the subsequent 700 °C tempering, and thus avoid the formation of coarse M23C6 distributed along Carbide cluster boundaries.
