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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.
Shizhong Wei - One of the best experts on this subject based on the ideXlab platform.
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effects of carbon on microstructures and properties of high vanadium high speed steel
Materials & Design, 2006Co-Authors: Shizhong Wei, Zhu Jinhua, Xu Liujie, Long RuiAbstract:Abstract The effects of carbon content on the microstructures, mechanical properties and wear behavior of high vanadium (10%) high speed steel were studied systemically. The results show that the Carbides in high vanadium high speed steel are composed of the vanadium carbide, small amount of Cr composite carbide and Mo composite carbide. With the increase of the carbon content, the amount of Carbides increases obviously, the shape of Carbides is changed from rod, strip to bulk, spherical, and the microstructures of metallic matrix are transformed from the ferrite, the mixture of ferrite, the martensite and retained austenite to the martensite and retained austenite. The hardness and the wear resistance of high vanadium high speed steel are increased, but its impact toughness would be decreased.
Al M Haik - One of the best experts on this subject based on the ideXlab platform.
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effect of carbon content on carbide morphology and mechanical properties of a r white cast iron with 10 12 tungsten
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: D Heydari, Alipour A Skandani, Al M HaikAbstract:Abstract Carbide morphologies of white cast iron containing 22% Cr and 10–12% tungsten with different carbon contents (2.34–3.20 wt.%) were investigated. Results indicated that for the as-cast alloys with no heat treatments, the addition of carbon changes the morphology of Carbides during air-cooling in the presence of tungsten. Light microscopy analysis revealed that for an alloy with 2.3 wt% carbon, chromium Carbides possess coarse gray appearance (GA). Increasing the carbon content reduced the coarse GA zones volume fraction while a finer GA zones emerged. The coexistence of coarse and fine GA phases came to an end at 2.8 wt% carbon, at which only fine GA zones spread throughout the chromium carbide phase. Scaling up the carbon content to 3.2 wt% led to the formation of tungsten carbide and austenite in a eutectic reaction. Both fine and coarse GA zones vanished while the tungsten Carbides acquired fishbone-like morphology. Upon heat treatment, the coarse GA zones vanished completely and turned into island appearance (IA) of chromium carbide. On the contrary, the finer GA zones remained unchanged after heat treatment and they coexisted with the IA. After heat treatment, the fishbone morphology shattered apart, however, the hyper chromium Carbides remained unchanged. X-ray diffraction, EDS, and electron microscopy identified the coarse GA zones microstructure to be mainly dendritic chromium carbide together with tungsten carbide and austenite phase residing in-between the chromium dendrites. After carrying out the proper heat treatment protocols, the chromium carbide in the coarse GA zones in the as-cast structure dissolved into tungsten carbide and martensite that were dispersed within the chromium carbide with island appearance (IA). Mechanical wear and hardness tests showed that the samples with higher IA volume fraction attained better wear resistance and higher hardness after heat treatment. The enhancement in the mechanical properties could be attributed to (i) the precipitation of chromium carbide in the form of IA morphology inhibited the crack propagation in the matrix. (ii) The precipitation of tungsten carbide both improved the matrix wear tolerance and promoted the transformation of austenite to a more wear-resistant and harder martensite phase.
