Single crystal superalloys of AM3 with different carbon levels were prepared at withdraw rate of 50μm/s. The effect of carbon addition on the carbide morphology was investigated. It was found that there were four typ...Single crystal superalloys of AM3 with different carbon levels were prepared at withdraw rate of 50μm/s. The effect of carbon addition on the carbide morphology was investigated. It was found that there were four types of MC-type carbides, acicular, nodular, blocky, and Chinese script-type in the crystals. With an increase in carbon level, the volume fraction of carbide increased significantly while the volume fraction of eutectic decreased significantly. Furthermore, the size of carbide in high level carbon alloy became much larger.展开更多
In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carb...In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carbide morphologies were investigated by scanning electron microscopy(SEM),and the electron probe microanalysis(EPMA) was used to characterize the carbide composition.The results indicate that the solidification rate is the important factor governing MC carbide growth morphology,size and distribution,composition and growth mechanism.With the increase of withdrawing rate,nodular,rod-like,Chinese script types of carbide morphology are observed.For the low withdrawing rate,with the increase of withdrawing rate,the carbide size becomes larger.For the case of dendritic interface,the carbide size becomes smaller with refinement of dendrites as withdrawing rate increases.The volume fraction of carbides increases with the withdrawing rate increasing.展开更多
The influence of rare earths content on carbide morphology and mechanical properties of wear resistance of white cast iron was studied by means of metallographic examination,scanning electron microscopic examination a...The influence of rare earths content on carbide morphology and mechanical properties of wear resistance of white cast iron was studied by means of metallographic examination,scanning electron microscopic examination and mechanical property test. The experiment results show that RE can change carbides from continuous network to isolated particles and improve the mechanical properties,especially in combination with proper heat treatment. The optimum properties of wear resistance of white cast iron modified by RE of 0.045% can be obtained by normalization at 960 ℃ for 2 h.展开更多
The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. T...The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.展开更多
Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundar...Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides were observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample with planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.展开更多
In order to review the effect of partial remelting time on the morphology of initial carbides, semisolid ingots of hypereutectic high Cr17 cast iron were remelted at 1270℃ for four different times, and the changing c...In order to review the effect of partial remelting time on the morphology of initial carbides, semisolid ingots of hypereutectic high Cr17 cast iron were remelted at 1270℃ for four different times, and the changing characteristics of shape factor and the equivalent diameter of initial carbides were analyzed quantitatively using a Leica image analyzer. The results indicate that firstly, the evolution process of the initial carbides' morphology undergoes melting, spheroidization and refining during the partial remelting; secondly, the solute diffusion and interface tension take dominant roles at the primary and the middle-final stages respectively in the process of initial carbide evolution; finally, a perfect structure can be obtained by remelting semisolid ingots at 1270℃ for 15 min.展开更多
Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from...Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40X10-6 to 320X10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into welldeveloped dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.展开更多
基金Project(51201130)supported by the National Natural Science Foundation of ChinaProject(2012JQ6005)supported by the Natural Science Basic Research Plan in Shaanxi Province of China+2 种基金Project(SKLSP201226)supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU,ChinaProject(11JK0805)supported by Scientific Research Program Funded by Shaanxi Provincial Education Department,ChinaProject(2010CV631201)supported by the National Basic Research Program of China
文摘Single crystal superalloys of AM3 with different carbon levels were prepared at withdraw rate of 50μm/s. The effect of carbon addition on the carbide morphology was investigated. It was found that there were four types of MC-type carbides, acicular, nodular, blocky, and Chinese script-type in the crystals. With an increase in carbon level, the volume fraction of carbide increased significantly while the volume fraction of eutectic decreased significantly. Furthermore, the size of carbide in high level carbon alloy became much larger.
基金Projects(50771081, 50931004) supported by the National Natural Science Foundation of ChinaProject(2010CB631202) supported by the National Basic Research Program of China
文摘In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carbide morphologies were investigated by scanning electron microscopy(SEM),and the electron probe microanalysis(EPMA) was used to characterize the carbide composition.The results indicate that the solidification rate is the important factor governing MC carbide growth morphology,size and distribution,composition and growth mechanism.With the increase of withdrawing rate,nodular,rod-like,Chinese script types of carbide morphology are observed.For the low withdrawing rate,with the increase of withdrawing rate,the carbide size becomes larger.For the case of dendritic interface,the carbide size becomes smaller with refinement of dendrites as withdrawing rate increases.The volume fraction of carbides increases with the withdrawing rate increasing.
文摘The influence of rare earths content on carbide morphology and mechanical properties of wear resistance of white cast iron was studied by means of metallographic examination,scanning electron microscopic examination and mechanical property test. The experiment results show that RE can change carbides from continuous network to isolated particles and improve the mechanical properties,especially in combination with proper heat treatment. The optimum properties of wear resistance of white cast iron modified by RE of 0.045% can be obtained by normalization at 960 ℃ for 2 h.
文摘The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.
文摘Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides were observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample with planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.
文摘In order to review the effect of partial remelting time on the morphology of initial carbides, semisolid ingots of hypereutectic high Cr17 cast iron were remelted at 1270℃ for four different times, and the changing characteristics of shape factor and the equivalent diameter of initial carbides were analyzed quantitatively using a Leica image analyzer. The results indicate that firstly, the evolution process of the initial carbides' morphology undergoes melting, spheroidization and refining during the partial remelting; secondly, the solute diffusion and interface tension take dominant roles at the primary and the middle-final stages respectively in the process of initial carbide evolution; finally, a perfect structure can be obtained by remelting semisolid ingots at 1270℃ for 15 min.
基金supported by the National Basic Research Program of China (Grant No. 2010CB631201)the National Natural Science Foundation of China (Grant No. 51201164)
文摘Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40X10-6 to 320X10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into welldeveloped dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.
