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PROPERTIES, WELDABILITY AND APPLICATIONS OF ADVANCED WROUGHT SUPERALLOYS FOR GAS TURBINE ENGINES
DLKlarstrom,VRIshwar,MDRowe,
D.L.Klarstrom
,V.R.Ishwar,M.D.Rowe

金属学报(英文版) , 2005,
Abstract: Alloy selection and alloy design both require consideration of an array of material attributes, including in-service properties, weldability and fabricability. Critical properties of advanced wrought superalloys for gas turbine applications include high temperature strength, thermal stability, oxidation resistance and fatigue resistance. In this paper, the properties of twelve wrought solid-solution-strengthened and six age-hardenable superalloys are compared. Weldability is an important attribute and can be a major limiting factor in the use of certain alloys. Weldability test methods are discussed and the resistance of alloys to solidification cracking and strain-age cracking is compared. The use of weldability testing in the development of modern wrought su-peralloys is discussed with several examples cited. Finally, alloy selection for gas turbine components is outlined, taking into account both alloy properties and fabricability.
CREEP AND FRACTURE OF SUPERALLOYSIN HOT CORROSION ENVIRONMENTS
热腐蚀环境中高温合金的蠕变与断裂

ZHANG Yuanhu,
张源虎

腐蚀科学与防护技术 , 1995,
Abstract: Process of creep and fracture of six types of superalloys which include wrought,conventional casting, directional solidification and single--crystal, in hot corrosion environmentswere studied. The fracture performane of alloys were discussed in terms of testing temperature,grain size and state of grain boundaries. The results showed that some kinds of severe corrosionand rupture might occurs in superalloys due to the interaction between creep stain and hot corrosion.
NEW DEVELOPMENTS IN WROUGHT 718-TYPE SUPERALLOYS
WDCao,RLKennedy,
W.D.Cao
,R.L.Kennedy

金属学报(英文版) , 2005,
Abstract: Research and development efforts are still very active on 718-type alloys although two major members of this widely used family, 718 and 625, were invented almost a half-century ago. Emphasis in this type of work at ATI Allvac is directed at improving existing alloys and developing new alloys to meet ever-increasing industrial demands. The improvement of existing alloys is exemplified by addition of minor elements P and B in alloy 718. The discovery of the beneficial effect of P and B in wrought alloy 718 led to development of a new, modified alloy, AllvacH 718 ERR. A large effort has also been directed at studying the effects of major element modifications in 718-type alloys, and a new alloy, AllvacR 718PlusTM, has been developed. The new alloy has much better high temperature capability, especially thermal stability, approaching the level of Waspaloy but retains excellent processing characteristics, similar to alloy 718. Alloy 718PlusTM should be useful in any 718-type application requiring a higher working temperature. The properties and processing of this alloy are introduced in this paper.
Variation in Creep Rupture of γ′ Strengthened Superalloys with Stacking Fault Energy of Matrices
阳志安,师昌绪,肖耀天
材料科学技术学报 , 1990,
Abstract: The correlation between the creep rupturebehaviour and the stacking fault energy of matricesof γ′strengthened superalloys has been studied dur-ing constant load creep.At high temperature andintermediate stress,the creep rupture time andstrain strongly depend on the stacking fault energyof matrices rather than the creep friction stress,butat higher stress,the role of grain boundary carbidesbecomes more obvious.However,in the considerably extensive stressrange investigated here,the mean creep rate is apower function of the stacking fault energy ofmatrices and the power index decreases with in-creasing initial applied stress.Particularly,at inter-mediate stresses the product of this index and theinitial applied stress compensated by the shearmodulus is same for two series of superalloys.Hence,this product may be a criterion predictingthat the matrix deformation controls high tempera-ture creep rupture.
EFFECT OF Mg CONTENT ON CREEP BEHAVIOUR OF Ni-BASE WROUGHT SUPERALLOY

KE Da'nian,ZHONG Zengyong,

金属学报 , 1983,
Abstract: The effect of addition of Mg on the creep behaviour of Ni-base wrought superalloy has been investigated. It was found that the trace Mg added may cause the alteration of continueous lath carbide into discontinueous massive one at the grain boundaries. It may also promote the spheroidization of the grain boundary carbide, decrease the diffusion coefficient of grain boundary and increase the activation energy for creep. The grain boundary energy and the boundary energy between grain boundary carbide and matrix are decreased and bonding strength of interface increased. Thus, the creep property and the creep-rupture life as well as the stress exponent of creep of the superalloy may be significantly improved by the impediment of the boundary sliding and the prevention of the nucleation and propagation of cracks.
Self-consistent Constitutive Modeling of the Creep Damage Behaviour of Nickel-base Directionally Solidified Superalloys with Different Grain Orientations
Zhufeng YUE,Zhenzhou LU,

材料科学技术学报 , 1998,
Abstract: A self consistent creep damage constitutive model is developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The model parameters are determined from the creep test data of single crystal and directionally solidified superalloy with a special grain orientation. The numerical analysis shows that the model creep damage behaviours of nickel-base directionally solidified superalloys with difFerent grain orientations are in good agreement with the experimental data.
Impact of Surface and Volume Modification of Nickel Superalloys IN-713C and MAR-247 on High Temperature Creep Resistance  [PDF]
M. Cie?la,F. Binczyk,M. Mańka
Archives of Foundry Engineering , 2012,
Abstract: Impact of surface and volume modification and double filtration during pouring the moulds on basic mechanical properties and creep resistance of nickel superalloys IN-713C and MAR-247 in conditions of accelerated creep of castings made of post-production scrap of these alloys is evaluated in this paper. The conditions of initiation and propagation of cracks in the specimens were analysed with consideration of stereological properties of material macro- and microstructure. It has been proven that in the conditions of high-temperature creep at 980°C and at stress σ = 150 MPa, creep resistance of superalloy MAR-247 is more than 10 times higher than the creep resistance of IN-713C alloy. In case of IN-713C alloy, the creep resistance negligibly depends on macrograin sizes. But, the macrograin size considerably affects the time to failure of specimens made of alloy MAR-247. Creep resistance of specimens made of coarse grain material was 20% higher than the resistance of fine grain materials.
EFFECT OF ZIGZAG GRAIN BOUNDARY ON CREEP RUPTURE OF A 10Cr-15Co-Ni-BASE WROUGHT SUPERALLOY

金属学报 , 1984,
Abstract: Investigation was made of the effect of the zigzag or straight grain boundary, which may be obtained by two different schemes of heat treatment, on the creep rupture of a 10Cr-15Co-Ni-base wrought superalloy, especially, on the reason whyits strength and plasticity at elevated temperature can be improved by the zigzaggrain boundary. It is shown that the zigzag grain boundary may delay the initiation, growth and propagation of crack, as well as may also influence the crack morphology and the fracture mode markedly. Furthermore, the zigzag grain boundary may intensively inhibit the grain boundary sliding and retard the crack joining, thus, force the bulk-grains to take part in more deformation. It displays an important role in the tertiary stage of creep. The creep life to failure of the alloy tested with zigzag grain boundary was increased by a factor of 1/4, and the plasticity was also improved slightly.
FATIGUE CRACK PROPAGATION OF Ni-BASE SUPERALLOYS
XBLiu,LZMa,KMChang,EBarbero,
X.B.Liu
,L.Z.Ma,K.M.Chang,E.Barbero

金属学报(英文版) , 2005,
Abstract: Time-dependent Fatigue Crack Propagation (FCP) behaviors of five Ni-base superalloys were investigated at various temperatures under fatigue with various holding times and sustained loading conditions.The new concept of damage zone is defined and employed to evaluate the alloys' resistance to hold-time FCP.A special testing procedure is designed to get the maximum damage zone of the alloys.Udimet 720 and Waspaloy show shorter damage zones than alloys 706 and 718.The fractographical analyses show that the fracture surfaces of the specimens under hold-time fatigue conditions are mixtures with intergranular and transgranular modes.As the extension of holding time per cycle, the portion of intergranular fracture increases.The effects of loading stress intensity, temperature, holding time, alloy chemistry, and alloy microstructure on damage zone and the crack growth behaviors are studied.Hold-time usually increases the alloy's FCP rate, but there are few exemptions.For instance, the steady state hold-time FCP rate of Waspaloy at 760℃ is lower than that without hold-time.The beneficial effect of hold-time was attributed to the creep caused stress relaxation during the hold-time.
NUMERICAL STUDY OF THE NOTCH EFFECT ON THE CREEP BEHAVIOR AND LIFE OF NICKEL-BASE SINGLE CRYSTAL SUPERALLOYS
QMYu,ZFYue,
Q.M.Yu
,Z.F.Yue

金属学报(英文版) , 2004,
Abstract: Numerical calculations of creep damage development and life behavior of circular notched specimens of nickel-base single crystal had been performed. The creep stress distributions depend on the specimen geometry. For a small notch radius, von Mises stress has an especial distribution. The damage distribution is greatly influenced by the notch depth, notch radius as well as notch type. The creep crack initiation place is different for each notched specimen. The characteristics of notch strengthening and notch weakening depend on the notch radius and notch type. For the same notch type, the creep rupture lives decrease with the decreasing of notch radius. A creep life model has been presented for the multiaxial stress states based on the crystallographic slip system theory.
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