ZHANG Hongxue XU Zhichao CHEN Guoliang University of Science and Technology Beijing
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Beijing
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China Professor
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Faculty of Superalloy
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University of Science and Technology Beijing
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Beijing
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China
金属学报(英文版)
The relative ratio of fatigue resistance to creep resistance of materials varies with test temper- ature.As the temperature decreases,the creep resistance,since it is a thermal activation pro- cess,becomes relatively larger than fatigue resistance.Therefore the fatigue damage becomes predominant,and results in expansion of fatigue fracture region(region F),and shrinkage even complete elimination of creep fracture region(region C).A materials parameter Ω can be defined to estimate the temperature at which the creep fracture region is completely de- pressed.This phenomenon could be understood on the basis of the integrated model of compet- itive and cumulative models of fatigue creep interaction.
关键词:
creep fracture
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null
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null
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null
Bangjie XIA+
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Hanyi LOU
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Lixin ZHANG
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Corrosion Science Laboratory
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Institute of Corrosion and Protection of Metals
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Academia Sinica
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Shenyang
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110015
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China
材料科学技术（英文）
The morphology and microstructure of magnetron sputtered coating of superalloy K38G on cast al- loy K38G have been investigated by means of SEM, TEM and XRD. The results indicate that the sputtered coating is identical to the substrate in chemical composition but it is composed only of γ phase without γ'. The sputtered superalloy coating presents columnar structure and the grain size is in the range of 20-100 nm. There are a great number of planar defects such as stacking faults and microtwins in the coating. The morphology and microstructure of the sputtered coating may have close relation to the remarkable increase of oxidation resistance of the coating.
关键词:
sputtering
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null
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null
J.M. Zhang
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L.Z. Ma
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J. Y. Zhuang
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Q. Deng
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J.H Du and Z. Y Zhong(Department of Superalloys
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Central Iron & Steel Research Institute
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Beijing 100081
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China)P. Janschek(Thyssen Umformtechnik GMBH
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42859 Remscheid
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Germany Manuscript received 26 August 1996)
金属学报(英文版)
Isothermal constant speed compression tests of superalloy IN718 were conducted using a computer-controlled MTS machine at temperatures from 960 to 1040℃, with initial strain rates from 0.001 s~(1) to 1.0 s~(1) and engineering strain from 0.1 to 0. 7.The variations of flow stress with deformation temperature, initial strain rate and engineering strain were analyzed in the paper. It was found that there was an obvious power-law relationship between flow stress and initial strain rate, which showed the behavior of strain rate hardening of superalloy IN718 at elevated temperatures.The relationship between flow stress and temperature could be described by an inverse trigonometric function.And the turning point on the curve may be related to the behavior of δ phase at 1000℃. Meanwhile, it was found that there was a complicated relationship between flow stress and strain,which was indicative of the comprehensive effect of work hardening and dynamic softening on flow stress during hot deformation. From the results of these tests, a constitutive equation of superalloy IN718 was developed.
关键词:
: constitutive relationship
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null
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null
材料科学技术（英文）
The oxidation behavior of a cast polycrystalline Co-base superalloy was studied at temperatures from 900 to 1050 degrees C 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 degrees C, which are controlled by the growth of the inner Cr-rich layer, and that after oxidation at 1050 degrees C 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 degrees C is composed of an outer layer of spinel and an inner continuous Cr-rich layer and at 1050 degrees C is composed of a very discontinuous Cr-rich layer.
关键词:
Co-base superalloy;Oxidation;Kinetics;Microstructure;coatings;alloys;aluminide;behavior;kinetics;air
Guichen HOU
材料科学技术（英文）
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.
关键词:
Co-base superalloy
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null
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null
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null
R.Noel
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D. Furrer
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G. Shen and J. Lemsky(Ladish Co.
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Inc.
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P.O. Box 8902
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Cudahy
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WI 53110-8902
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USA Manuscript received 26 Augnst 1996)
金属学报(英文版)
Optimum properties of high temperature superalloys are derived from interactions of the composition,thermomechanical deformation, and heat treatment.Nickel-base alloys contain a variety of alloying elements in a large number of combinations to produce various desired effects. The general characteristics of any specific nickelbase superalloy is determined by composition.The control of the microstructure in wrought processed superalloys can further influence the resultant component properties.The relationship between microstructure and properties is key in advanced design and manufacture of turbine engine components, and requires extensive alloy and process characterization to achieve desired results.Various forging methods have been developed and employed throughout the years to process superalloy components.Hammer forging, Press forging,and advanced isothermal press forging equipment and processes have been designed and manufactured to process speciality metals which often have very narrow processing windows.Combination processes have also been introduced into turbine engine applications,which result in a hybrid of resultant structures and properties.One such speciality,combination process is the Ladish Iso Con process which utilizes isothermal forging and conventional forging to achieve unique properties not matched by any other single process.Ladish utilizes forging presses for conventional forging, hot-die forging and for isothermal forging, in addition to hammers and ring rolling mills for wrought processing.This wide range of equipment allows flexibility in process design and optimization.Variations in temperature, strain and strain rate have been shown to significantly influence resultant grain sizes and microstructures.Tools are being developed to allow forging processes and specific forging parameters to be evaluated and optimized with regard to final microstructure before shop triale are required. Sophisticated finite element method (FEM) models are allowing the design of forging processes on computers rather than by iterative trial and error methods.
关键词:
:forging
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null
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Materials Letters
It is proposed that the growing carbide in a directional solidified nickel-based superalloy is a dissipation structure. The morphology, formation mechanism and dissipationality of the carbide have been studied.
关键词:
ZHANG Bing
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TAO Chun-hu
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LU Xin
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LIU Chang-kui
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HU Chun-yan
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BAI Ming-yuan
钢铁研究学报(英文版)
A series of experiments of investigating the recrystallization of single crystal DD3 superalloy were carried out. The threshold temperature for recrystallization and the effect of annealing temperature on recrystallization were studied. The results show that the threshold temperature for recrystallization of the shotpeened DD3 samples is between 1 000 ℃ and 1 050 ℃ under the condition of annealing for 2 h, and the recrystallization depth increases with the rise of the annealing temperature. Below 1 150 ℃, the recrystallization depth increases slowly with the temperature climbing, while above 1 150 ℃, the recrystallization depth increases quickly with the rise of the temperature. The solution of the γ′ phase is a critical factor of the recrystallization behavior of DD3 superalloy. In addition, the kinetics and microstructural evolution of recrystallization at 1 200 ℃ were also studied. It is found that the recrystallization progresses rapidly at 1 200 ℃ through the growth of fully developed recrystallized grains, and the recrystallization process on the shotpeened surface is similar to that of wrought materials, including nucleation of recrystallization, growth of new grains into the matrix, and growth of new grains by swallowing up each other.
关键词:
single crystal superalloy;recrystallization;shot peening
Huanming CHEN
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Benfu HU
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Yiwen ZHANG
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Huiying LI
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Quanmao YU
材料科学技术（英文）
In order to investigate the influence of processing parameters on the granularity distribution of superalloy powders during the atomization of plasma rotating electrode processing (PREP), in this paper FGH95 superalloy powders is prepared under different processing conditions by PREP and the influence of PREP processing parameters on the granularity distribution of FGH95 superalloy powders is discussed based on fractal geometry theory. The results show that with the increase of rotating velocity of the self-consuming electrode, the fractal dimension of the granularity distribution increases linearly, which results in the increase of the proportion of smaller powders. The change of interval between plasma gun and the self-consuming electrode has a little effect on the granularity distribution, also the fractal dimension of the granularity distribution changed a little correspondingly.
关键词:
FGH95 superalloy powders
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null
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null
