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Characteristics of High Temperature Rupture of a Cast Ni-Based Superalloy M963
Chao YUAN,Xiaofeng SUN,Fengshi YIN,Hengrong GUAN,Zhuangqi HU,Qi ZHENG,Yang YU,

材料科学技术学报 , 2001,
Abstract: The rupture behavior of a cast Ni-base superalloy M963 at high temperature has been investigated. The microstructure examination shows that there exists a large amount of the carbide and gamma-gamma ' eutectic, which is very harmful to the mechanical properties of M963 superalloy. The tensile strength of M963 superalloy both at room temperature and at high temperatures is higher than that of K17G alloy, but the tensile ductility of the former is much lower than that of the latter. In tensile fracture process with the high strain rate, the open carbides are the initiation site and the carbide/matrix interface is the propagation path of cracks. But in fracture process with the low strain rate, the carbide/matrix interface and cast microvoids are the initiation sites, and the carbide/matrix interface is the propagation path of cracks. The effective ways to improve ductility of M963 superalloy are also suggested.
Effect of a high magnetic field on the shape of the γ′ precipitates in cast nickel-based superalloy K52

X Ren,GQ Chen,WL Zhouy,CW Wu,C Yuan,JS Zhang,

材料科学技术学报 , 2009,
Abstract: The shape change of the γ' precipitates of cast Ni-based superalloy K52 after aging treatment under a high magnetic field was investigated. The results show that duplex γ' precipitates are present in the γ matrix after aging treatment with or without the magnetic field. One is the coarse particles with average size of 500 nm; the other is fine spherical γ' precipitates with average of 100 nm in diameter. The application of a 10T magnetic field only results in the shape of the coarse γ' particles changing from spherical to cuboidal when the alloys subjected to the same heat treatments. This shape change was mainly discussed based on the strain energy increase caused by the difference in magnetostriction between the γ matrix and γ' precipitates. The fine γ' particles still keep spherical. Further TEM observations shows that a number of γ particles in nano-scale precipitate in the coarse γ' particles in the specimens treated without the magnetic field. In addition, it was found that the magnetic field caused the decrease of the hardness in the alloy, and the hardness was associated with the field direction.
ZHANG Bingda TONG Yingjie ZHANG Jiayuan LIU Zezhou ZHU Yaoxiao Institute of Metal Research,Academia Sinica,Shenyang,China,
ZHANG Bingda TONG Yingjie ZHANG Jiayuan LIU Zezhou ZHU Yaoxiao Institute of Metal Research
,Academia Sinica,Shenyang,China

金属学报(英文版) , 1991,
Abstract: In comparison with conventional superalloys,no carbide but significant amount ofγ+M_3B_2 and γ+γ′ eutectics were revealed to precipitate in the stable as-cast structure ofNi-base superalloy M91 which is abundant in B and minfied in C.During solidification ofthe superalloy,the residual liquid is much less and the tendency to porousness isinconsiderable.This superalloy seems to be available for turbine blade and other integral cast-ings under intermediate temperature and long-term services.
SUN Jian ZHANG Yuanhu HU Gengxiang Shanghai Jiaotong University,Shanghai,China SUN Jian,lecturer,
SUN Jian ZHANG Yuanhu HU Gengxiang Shanghai Jiaotong University
,Shanghai,China SUN Jian,lecturer

金属学报(英文版) , 1993,
Abstract: The creep crack propagation in superalloy René80 of two different microstructures,i.e., equiaxed grain structure by conventional casting and columnar grain by directional solidification,was investigated under static load at 1123 K.The creep crack growth rate, da/dt,seems to be correlated with the stress intensity factor,K.The creep crack growth rate in the directionally solidified alloy is lower than that in the conventional cast alloy,owing to the elimination of transverse grain boundaries.The effect of microstructure on creep crack propagation has also been discussed.
Property Enrichment of Aged Nickel Base Superalloy Supercast 247A
Lavakumar Avala,Ch.V.S. Murthy 2,Prince Kr singh 3,Bhargav Chaitanya 4
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2013,
Abstract: The commercial nickel-base superalloy Supercast 247A can be used for applications in which is required high mechanical strength and corrosion resistance at elevated temperatures, such as turbine blades and automotive turbocharger rotors. The mechanical properties are totally connected to the morphology, size and distribution of γ' phase and carbides. In order to improve the mechanical properties, the material is subjected to solution and aging heat treatment, to raise the volume fraction of γ' phase in the matrix and to form carbides at grain boundaries. In the present study the Supercast 247A superalloy was remelted and cast to obtain the desired polycrystalline test bars by controlling casting parameters, followed by the investigation of precipitation morphology and mechanical properties with respect to solution treatment and aging treatment. The experimental results show that by well controlled casting parameters the Supercast 247A owns excellent castability to form a superalloy with fine grain structure, resistance to indentation as well as superior strength.
Oxidation of a Co-base Superalloy

Guichen HOU Zhiyuan LIU,Hua WEI Qi ZHENG Xiaofeng SUN Hengrong GUAN Zhuangqi HU Superalloy Division,

材料科学技术学报 , 2008,
Abstract: The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050℃ and analyzed by thermogravimetric analysis (TGA),X-ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate that a cast Co-base superalloy follows the subparabolic oxidation kinetics at 900 and 1000℃,which are controlled by the growth of the inner Cr-rich layer,and that after oxidation at 1050℃ for 200 h,it almost exhibits the linear oxidation kinetics possible due to the volatility of Cr-rich oxide.A mixed scale forms on the alloy after prolonged oxidation.The oxide scale formed at 900 and 1000℃ is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at 1050℃ is composed of a very discontinuous Cr-rich layer.
Effect of Phosphorus on Microstructure and High Temperature Properties of a Cast Ni-base Superalloy
Effect of Phosphorus on Microstructure and High Temperature Properties of a Cast Ni—base Superalloy

Chao YUAN,Fengshi YIN,Xiaofeng SUN,Hengrong GUAN,Zhuangqi HU,

材料科学技术学报 , 2002,
Abstract: Effect of phosphorus on the microstructure and high temperature properties of a cast Ni-base superalloy M963 has been investigated. SEM observation and EDS analysis showed that P was mostly enriched in the interdendritic region, and the P-rich phase was formed in the front position of finally solidified eutectics in high P doped alloys. It was found that the P-rich phase, as preferred initiation and propagation site of cracks, could aggravate the fracture process at high temperature in high P doped alloys. Consequently, high P addition would reduce remarkably the ductility and creep life of M963 superalloy at high temperature.

BAI Yuankai,

金属学报 , 1983,
Abstract: The effect of cyclic stress on the strength of creep rupture and recurrent creep rupture as well as low cycle fatigue of a cast nickel-base superalloy with high Al and Ti contents has been studied under different temperature and stress. It was found that the temperature is the main factor influenced upon the creepfatigue interaction. There are three temperature ranges leading to damage of creep, fatigue or combination of creep-fatigue individuaUy. The tested results were identified by some SEM fractographs.
Surface modification, microstructure and mechanical properties of investment cast superalloy  [PDF]
M. Zielińska,K. Kubiak,J. Sieniawski
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The aim of this work is to determine physical and chemical properties of cobalt aluminate (CoAl2O4) modifiers produced by different companies and the influence of different types of modifiers on the grain size, the microstructure and mechanical properties of high temperature creep resisting superalloy René 77.Design/methodology/approach: The first stage of the research work took over the investigations of physical and chemical properties of cobalt aluminate manufactured by three different companies: Remet, Mason Color and Permedia Lublin. There were determined the grain size distribution of cobalt aluminate powder, the average diameter of the powder particles, phase composition, cobalt contamination. In the next step, the ceramic moulds were made with different kind of cobalt aluminate (Mason Color, Remet, Permedia Lublin) and its concentration (0.5%) in the primary slurry. The samples of stepped and cylindrical shape were poured in the ceramic moulds prepared earlier. The average grain size of the γ phase, was determined on the stepped samples. The microstructure investigations let to examine the influence of the surface modification on the morphology of γ ‘ - phase and carbides precipitations. Samples were turned from cylindrical castings for mechanical properties investigations: creep tests.Findings: Modification of the face coat of ceramic mould results in the reduction of the grains size of γ matrix and disintegration of carbide precipitates. It results in the improvement of mechanical properties of the alloy. On the grounds of the obtained results, it was found that the type of used modifier influenced the grain size of the alloy and its mechanical properties.Research limitations/implications: The established physical and chemical properties of modifier let to get better control of grain size of the castings and their quality what will result in decrease of defective products.Originality/value: It was proved that the effectiveness of cobalt aluminate modifier as an inoculant depends not only on its concentration in ceramic slurry but on its chemical composition. The researches allowed to find the optimal concentration of Co in CoAl2O4 to produce casting elements made from superalloy René 77.
Influence of cooling rate on y'morphology in cast Ni – base superalloy  [PDF]
J. Belan
Archives of Foundry Engineering , 2009,
Abstract: The Ni – base superalloys, which are combined an unique physical and mechanical properties, are used in aircraft industry for productionof aero engine most stressed parts, as are turbine blades. From this reason a dendrite arm spacing, carbides size and distribution, morphology,number and value of y'- phase are very important structural characteristics for blade lifetime prediction as well as aero engine its self. In this article are used methods of quantitative metallography (software LUCIA for carbides evaluation, measuring of secondary dendrite arm spacing and coherent testing grid for y' - phase evaluation) for evaluation of structural characteristics mentioned above on experimental material – Ni base superalloy S6K. The high temperature effect represented here by heat treatment at 800°C followed with holding time about 10 hours, and cooling rate, here represented by three various cooling mediums as water, air, and oil, on structural characteristics and application of quantitative methods evaluation are presented in this paper.
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