The microstructures of base/modified RR2072 SX superalloys and their effects on creep properties at elevated temperatures

Chen, Q.Z; Jones, Nicholas F.; Knowles, David

doi:10.1016/s1359-6454(01)00410-4

Cited by 163 publications

(75 citation statements)

References 6 publications

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“…MC particles in the interdendritic regions have a NaCl crystal structure, and their orientation relationship with the matrix is {100} MC//{100} matrix with h001iMC//h001i matrix [28]. The high tantalum and niobium, together with molybdenum in the present MC carbides strengthen the binding forces in MC particles such an extent that MC particles can keep stable in the deformation microstructure of DD32 alloy [15].…”

Section: Discussionmentioning

confidence: 88%

Rotary bending high-cycle fatigue behavior of DD32 single crystal superalloy containing rhenium

Yang

Sun

et al. 2012

J Mater Sci

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Smooth and notched specimens of single crystal superalloy DD32 were subjected to rotary bending highcycle fatigue (HCF) loading at different temperatures. The experimental results demonstrate that fatigue strengths of the smooth and notched specimens reach the maxima and the minimum notch sensitivity displays at 760°C. DD32 alloy exhibits excellent HCF properties compared to SRR99 alloy under the same test condition. As for the smooth specimens, slip bands moving through c and c 0 phases as well as dislocation bowing are the main deformation modes. As for the notched specimens, the deformations are carried out by dislocation loop bowing and shearing of PSBs mode at intermediate temperatures; at 900°C, the minimum fatigue strength results from dislocation climbing deformation and the degradation of c 0 precipitates. The fine secondary c 0 precipitates advantage the recovery of dislocations and further deformation of the fatigue specimens.

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Section: Discussionmentioning

confidence: 88%

Rotary bending high-cycle fatigue behavior of DD32 single crystal superalloy containing rhenium

Yang

Sun

et al. 2012

J Mater Sci

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“…Under the applied load, these interfaces, because of high stress concentration and interfacial energy, tend to become the favored initiation sites and propagation paths of microcracks. [15] Because microcracks promote the fracture of superalloys and contribute to the reduction of service life, [5,[18][19][20] MC degeneration, which results in more frequent cracking than the intact MC, is undoubtedly deleterious to the thermally exposed K452 alloy. A considerable amount of degenerated, coarse, and irregular MC carbides distributed at the GBs are especially more detrimental than when they are in the GIs.…”

Section: Primary MC Degenerationmentioning

confidence: 99%

“…[21] However, the following aspects determine the inappreciable influence of M 23 C 6 on mechanical properties: (1) the population of M 23 C 6 is small, less than 1.3 pct in volume fraction; (2) the precipitation and coarsening of M 23 C 6 -c¢ cells remove much of solid solution strengthening elements, that is, Cr, W, Mo, Al, and Ti, from the c matrix and weaken the alloy; [5,22] and (3) M 23 C 6 particles mainly distribute in the interdendritic regions and often crowd in the form of loops, chains, or clusters, as demonstrated in Figure 6, so that their resistance to dislocation motion is discounted severely. …”

Section: Precipitation and Evolution Of M 23 C 6 Carbides Within Gismentioning

confidence: 99%

“…[2][3][4][5][6] These processes remove much of strengthening elements from the c matrix and significantly degrade the properties of the alloys, such as mechanical properties, corrosion resistance and service life. In this article, the microstructural evolution during long-term thermal exposure in the K452 alloy is examined in detail, and the microstructure-property relationships are explored carefully.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Long-Term Thermal Exposure on the Microstructure and Properties of a Cast Ni-Base Superalloy

Qin

Guo

Yuan

et al. 2007

Metall Mater Trans A

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Microstructural stability and microstructure-property relationship during long-term thermal exposure in K452 alloy (a new Ni-base cast superalloy with~21 pct Cr, 11 pct Co, 3.5 pct W, 2.5 pct Al, 3.5 pct Ti, and others) are investigated. It is found that exposure temperature and time have significant effects on the microstructure and properties of the alloy. During exposure, the microstructure is degraded by c¢ coarsening, MC carbide (M mainly represents Ti, W, and Nb) degeneration, precipitation and evolution of grain interior (GI) M 23 C 6 carbide, evolution of grain boundary (GB) microstructure, and precipitation of g phase. Among them, the c¢ coarsening is the leading reason for the decrease of strength of the alloy. The GI M 23 C 6 and the g phase have negligible influence on the properties due to their relatively small populations. Blocky, closely spaced GB M 23 C 6 particles engulfed in c¢ increase the stress-rupture life, whereas the formation of a continuous GB M 23 C 6 chain has an opposite effect. A life peak occurs when the M 23 C 6 /c¢ structure at the GBs is in an optimal form. The degenerated MC is the preferred initiation site of microcracks. Its presence at the GBs promotes the onset of intergranular fracture, and leads to the decrease in mechanical properties.

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“…New generation single-crystal (SC) superalloys, which are supposed to be free of grain boundaries, have been, however, found to contain crystal boundaries with a misorientation in the range of 12 to 15 deg, which is on the border between low-and high-angle boundaries, particularly, in large castings. [1,2] Consequently, in order to improve high-temperature mechanical properties of SC alloys containing these defects and to increase intergranular strength in other polycrystalline directionally solidified (DS) superalloys, addition of grain boundary strengthening elements is commonly employed. Boron is an essential minor elemental addition to these heat-resistant materials primarily to improve their creep rupture properties.…”

mentioning

confidence: 99%

Analytical Electron Microscopy Study of Boron-Rich Grain Boundary Microconstituent in Directionally Solidified RENE 80 Superalloy

Ojo

Zhang

2008

Metall Mater Trans A

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Analytical transmission electron microscopy study of intergranular regions in directionally solidified (DS) RENE 80 superalloy was performed. In addition to the generally reported M 3 B 2 -type boride particles that form in the alloy during ingot solidification, considerable presence of a different type of boride particles, M 5 B 3 , which has not been generally reported in the alloy, was observed. Extensive formation of these particles along the grain boundaries in the DS alloy is pertinent to hightemperature performance of the material.The ever-increasing quest for higher operating temperatures in aero and industrial gas turbine engines has resulted in c¢ precipitation-strengthened nickel base superalloys that are free or contain reduced number of grain boundaries by directional solidification casting route. New generation single-crystal (SC) superalloys, which are supposed to be free of grain boundaries, have been, however, found to contain crystal boundaries with a misorientation in the range of 12 to 15 deg, which is on the border between low-and high-angle boundaries, particularly, in large castings. [1,2] Consequently, in order to improve high-temperature mechanical properties of SC alloys containing these defects and to increase intergranular strength in other polycrystalline directionally solidified (DS) superalloys, addition of grain boundary strengthening elements is commonly employed. Boron is an essential minor elemental addition to these heat-resistant materials primarily to improve their creep rupture properties. [3,4] Nevertheless, it has been recognized that the mode in which boron exists on grain boundary regions, either in austenitic solid solution form or selectively partitioned into second-phase particles, can significantly influence the creep properties of superalloys. [5,6] Experimental investigation is crucial in establishing the presence and nature of intergranular borides in multicomponent superalloys due to the influence of interfacial elemental segregation that is not generally considered during thermodynamic equilibrium calculations of theoretical models. [7] High-temperature alloy development has resulted in casting of conventional boron-bearing RENE* 80 by directional solidification process to produce DS RENE 80 superalloy. The cast material is normally subjected to solution heat treatment, gas-fan cooled, and followed by aging prior to deployment to service. Limited information is presently available about the mode of the presence of boron along intergranular regions in the DS RENE 80, which can be crucial in understanding microstructural response of the alloy to mechanical loading during long-term high-temperature exposure. The primary goal of the present work was, therefore, to perform analytical transmission electron microscopy (TEM) study of solution heat-treated, gas-fan cooled, and aged DS RENE 80 superalloy to ascertain the nature of boron presence along its intergranular regions. The composition of the DS RENE 80 material used in the study was (wt pct) 0. 2C, 14.1Cr, 9.52Co...

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The microstructures of base/modified RR2072 SX superalloys and their effects on creep properties at elevated temperatures

Cited by 163 publications

References 6 publications

Rotary bending high-cycle fatigue behavior of DD32 single crystal superalloy containing rhenium

Rotary bending high-cycle fatigue behavior of DD32 single crystal superalloy containing rhenium

Effects of Long-Term Thermal Exposure on the Microstructure and Properties of a Cast Ni-Base Superalloy

Analytical Electron Microscopy Study of Boron-Rich Grain Boundary Microconstituent in Directionally Solidified RENE 80 Superalloy

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