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Cobalt_superalloys_composition(1).txt
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Cobalt_superalloys_composition(1).txt
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FN Clarivate Analytics Web of Science
VR 1.0
PT J
AU Berthod, P
Gomis, JP
AF Berthod, Patrice
Gomis, Jean-Paul
TI Improvement of the high temperature oxidation of TaC-strengthened
Co(Cr)-based cast superalloys by the addition of nickel
SO CORROSION ENGINEERING SCIENCE AND TECHNOLOGY
AB In this work, nickel is added in substitution to cobalt in the composition of a cast cobalt-based chromium-rich superalloy designed to obtain a double-phased {fcc matrix + TaC} microstructure. Two nickel amounts were tested, 13 and 26 wt-%Ni, for 25 wt-%Cr, 0.4 wt-%C and 6 wt-%Ta, the rest being cobalt. The obtained as-cast microstructures are not different from the starting alloy's one, contrarily to the hardness which became lower. The oxidation tests at 1200 degrees C for 170 h demonstrated a significant improvement of the alloy's behaviour, especially for an addition of 26 wt-%Ni. This seems to be attributed to an easier Cr diffusion towards the oxidation front as suggested by the observed Cr contents in extreme surface as well as by the lower Cr concentration gradients. In addition, the TaC seemed to be morphologically more stable in the presence of nickel in the alloys than in the absence of Ni.
SN 1478-422X
EI 1743-2782
DI 10.1080/1478422X.2019.1699261
EA DEC 2019
UT WOS:000500624100001
ER
PT J
AU Reynolds, TD
Collins, DM
Soor, NK
Street, SR
Warnken, N
Mignanelli, PM
Hardy, MC
Evans, HE
Taylor, MP
AF Reynolds, T. D.
Collins, D. M.
Soor, N. K.
Street, S. R.
Warnken, N.
Mignanelli, P. M.
Hardy, M. C.
Evans, H. E.
Taylor, M. P.
TI Identifying heating rate dependent oxidation reactions on a nickel-based
superalloy using synchrotron diffraction
SO ACTA MATERIALIA
AB Synchrotron grazing incidence X-ray diffraction has been used to newly reveal the heating rate dependent oxidation reactions that develop on a polycrystalline nickel-based superalloy. A continuous layer of precursor oxide was shown to form during the heating stage. Their approximate growth rates, their effect on local surface compositions of the alloy substrate, and their degree of interface planarity are considered critical in determining subsequent oxidation reactions when held for extended thermal exposures. The precursor oxides were predominantly nickel or cobalt based (NiO/CoO and Co3O4/NiCo2O4). Following the fastest heating rates (40 degrees C min(-1) and above), the stable Cr2O3 phase formed, inhibiting Ni or Co diffusion to the surface. At slower heating rates (10-20 degrees C min(-1)), no evidence of the stable Cr2O3 was found, even after 200 h at elevated thermal exposure, instead continued growth of the precursor oxides was observed. Heating at 5 degrees C min(-1) gave rise to an intriguing zone where sufficient precursor and favourable kinetics enabled the formation of a spinel, NiCr2O4, surface layer. Cross sections observed with electron microscopy confirmed this to be planar and continuous. Heating at the slowest tested 2 degrees C min(-1) contrarily gives a non-protective surface layer comprising an outwardly growing NiO/CoO precursor oxide on top of an inwardly growing mixed oxide. The quantities, interfacial morphologies of oxides of the precursor oxide grown and the possible thermodynamic reactions that lead to their formation are discussed. Crown Copyright (C) 2019 Published by Elsevier Ltd on behalf of Acta Materialia Inc. All rights reserved.
OI Collins, David/0000-0003-2458-9713
SN 1359-6454
EI 1873-2453
PD DEC
PY 2019
VL 181
BP 570
EP 583
DI 10.1016/j.actamat.2019.10.019
UT WOS:000498749300050
ER
PT J
AU Lenz, M
Wirth, J
Englisch, S
Rosiwal, J
Buchinger, N
Weiser, M
Virtanen, S
Zubiri, BA
Spiecker, E
AF Lenz, Malte
Wirth, Janis
Englisch, Silvan
Rosiwal, Jan
Buchinger, Nadine
Weiser, Martin
Virtanen, Sannakaisa
Zubiri, Benjamin Apeleo
Spiecker, Erdmann
TI Correlative Nano-Computed Tomography and Focused Ion-Beam Sectioning: A
Case Study on a Co-Base Superalloy Oxide Scale
SO ADVANCED ENGINEERING MATERIALS
AB Herein, the capabilities of a correlative tomography approach combining laboratory nano X-ray computed tomography, focused ion-beam sectioning, and energy-dispersive X-ray spectroscopy are utilized for the characterization of multilayered oxide scales of Co-base superalloys regarding their 3D morphology and chemical composition. The combination of complementary 3D imaging techniques allows for a precise and reliable segmentation of the pore space, oxide precipitates, and different phases of the initial material. Such information is instrumental to a microscopic understanding of oxidation in this new class of superalloys and key to improvement of oxidation resistance in the next-generation high-temperature materials.
SN 1438-1656
EI 1527-2648
AR 1900823
DI 10.1002/adem.201900823
EA NOV 2019
UT WOS:000495518800001
ER
PT J
AU Sauza, DJ
Dunand, DC
Seidman, DN
AF Sauza, Daniel J.
Dunand, David C.
Seidman, David N.
TI Microstructural evolution and high-temperature strength of a
gamma(f.c.c.)/gamma '(L1(2)) Co-Al-W-Ti-B superalloy
SO ACTA MATERIALIA
AB We characterized the microstructural features and mechanical performance of a model Co-5.6Al-5.8W-6.6Ti-0.12B (at.%) alloy consisting of gamma(L1(2))-precipitates in a gamma(f.c.c.)-matrix. Scanning electron microscopy (SEM) was used to follow the isothermal aging of the micro-structure at 900 and 1000 degrees C for 256 h, and 950 degrees C for 1000 h. The compositions of the gamma'(L1(2))-precipitates and gamma(f.c.c.)-matrix were evaluated by atom-probe tomography (APT) for solution-treated and air-cooled conditions, as well as in specimens aged at 950 degrees C for 16 and 100 h. Boron was shown to partition preferentially to the gamma'(L1(2))-precipitates, and profiles taken across the gamma(f.c.c.)-matrix channels in both aged specimens revealed confined segregation of A1 at one of the two gamma(f.c.c.)/gamma'(L1(2)) heterophase interfaces. After aging at 950 degrees C for 16 h, Co-5.6Al-5.8W-6.6Ti-0.12B (at.%) exhibited anomalous flow-strength behavior in the range 625-900 degrees C with a peak yield stress of 822 MPa between 800 and 825 degrees C. Compressive creep tests performed at 850 degrees C demonstrated a creep strength comparable to archival literature results for Co-9Al-9W-0.12B (at.%), despite a smaller gamma'(L1(2))-volume fraction and lack of strengthening borides along the grain boundaries (GBs). The activation energy for creep in the temperature range 800-900 degrees C was 606 kJ mol(-1). The post-creep microstructure consists of rafted gamma'(L1(2))-precipitates perpendicular to the compression axis, consistent with the positive gamma(f.c.c.)/gamma'(L1(2)) lattice parameter misfit character of this class of alloys. Creep failure could occur due to GB embrittlement caused by deleterious Ti-rich (L2(1) or B2) and D0(19) phases formed at the GBs during creep. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
SN 1359-6454
EI 1873-2453
PD AUG 1
PY 2019
VL 174
BP 427
EP 438
DI 10.1016/j.actamat.2019.05.058
UT WOS:000474501300041
ER
PT J
AU Tirado, FLR
Taylor, S
Dunand, DC
AF Tirado, Fernando L. Reyes
Taylor, Spencer
Dunand, David C.
TI Effect of Al, Ti and Cr additions on the gamma-gamma' microstructure of
W-free Co-Ta-V-Based superalloys
SO ACTA MATERIALIA
AB The recently-discovered metastable gamma'-Co-3(Ta0.76V0.24) phase formed on aging in a Co-6Ta-6V (at.%) ternary alloy is stabilized by partial replacement of Ta and V with Al and Ti. In two alloys with composition Co-6Al-3Ta-3V and Co-5Al-3Ta-3V-1Ti with gamma+gamma' microstructure, the gamma'-precipitates remain stable for up to 168 h at 850 and 900 C, with no precipitation of additional phases. Adding Ni and B and doubling the Ti concentration produces a gamma/gamma' superalloy, Co-10Ni-5Al-3Ta-3V-2Ti-0.04B (at.%), with gamma' precipitates which are stable up to six weeks of aging at 850 degrees C, while slowly coarsening and coalescing from cuboidal to elongated shapes. After one day of aging at 850 degrees C, the gamma' nanoprecipitates have a (Co0.83Ni0.17)(3)(Ta0.42Al0.23Ti0.19V0.15B0.01) composition, with Al and Ti replacing at the same rate both Ta and V in the original metastable Co-3(Ta0.76V0.24) phase. To improve oxidation resistance, 4% Cr is added to the new superalloy, resulting in a somewhat higher volume fraction of finer cuboidal gamma' precipitates after one week of aging at 850 degrees C, but no other deleterious phases. These W-and Mo-free gamma/gamma' superalloys show good creep resistance at 850 degrees C, on par with two other recent Co-base gamma/gamma' superalloys: (i) Co-9W-9Al-8Cr (at.%) which has higher density due to its high W content, and (ii) Co-30Ni-10Al-5Mo-2Nb (at.%) which has lower density (as it is W-free) but contains triple the Ni concentration. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Dunand, David C/B-7515-2009
OI Reyes Tirado, Fernando/0000-0003-4594-6185
SN 1359-6454
EI 1873-2453
PD JUN 15
PY 2019
VL 172
BP 44
EP 54
DI 10.1016/j.actamat.2019.04.031
UT WOS:000470946500005
ER
PT J
AU Pandey, P
Sawant, AK
Nithin, B
Peng, Z
Makineni, SK
Gault, B
Chattopadhyay, K
AF Pandey, P.
Sawant, A. K.
Nithin, B.
Peng, Z.
Makineni, S. K.
Gault, B.
Chattopadhyay, K.
TI On the effect of Re addition on microstructural evolution of a
CoNi-based superalloy
SO ACTA MATERIALIA
AB In this study, the effect of rhenium (Re) addition on microstructural evolution of a new low-density Co-Ni-Al-Mo-Nb based superalloy is presented. Addition of Re significantly influences the gamma' precipitate morphology, the gamma/gamma' lattice misfit and the gamma/gamma' microstructural stability during long term aging. An addition of 2 at.% Re to a Co-30Ni-10Al-5Mo-2Nb (all in at.%) alloy, aged at 900 degrees C for 50 h, reduces the gamma/gamma' lattice misfit by similar to 40% (from +0.32% to +0.19%, measured at room temperature) and hence alters the gamma' morphology from cuboidal to round-cornered cuboidal precipitates. The composition profiles across the gamma/gamma' interface by atom probe tomography (APT) reveal Re partitions to the gamma phase (K-Re = 0.34) and also results in the partitioning reversal of Mo to the gamma phase (K-Mo = 0.90) from the gamma' precipitate. An inhomogeneous distribution of Gibbsian interfacial excess for the solute Re (Gamma(Re), ranging from 0.8 to 9.6 atom.nm(-2)) has been observed at the gamma/gamma' interface. A coarsening study at 900 degrees C (up to 1000 h) suggests that the coarsening of gamma' precipitates occurs solely by evaporation-condensation (EC) mechanism. This is contrary to that observed in the Co-30Ni-10Al-5Mo-2Nb alloy as well as in some of the Ni-Al based and high mass density Co-Al-W based superalloys, where gamma' precipitates coarsen by coagulation/coalescence mechanism with an extensive alignment of gamma' along <100> directions as a sign of microstructural instability. The gamma' coarsening rate constant (K-r) and gamma/gamma' interfacial energy are estimated to be 1.13 x 10(-27) m(3)/s and 8.4 mJ/m(2), which are comparable and lower than Co-Al-W based superalloys. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Peng, Zirong/AAG-9378-2019
OI Peng, Zirong/0000-0001-7844-8313
SN 1359-6454
EI 1873-2453
PD APR 15
PY 2019
VL 168
BP 37
EP 51
DI 10.1016/j.actamat.2019.01.046
UT WOS:000464086500004
ER
PT J
AU Sani, SA
Arabi, H
Kheirandish, S
Ebrahimi, G
AF Sani, Saeed Aliakbari
Arabi, Hossein
Kheirandish, Shahram
Ebrahimi, Golamreza
TI Investigation on the homogenization treatment and element segregation on
the microstructure of a /-cobalt-based superalloy
SO INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS
AB The aim of the present study was to investigate the effect of element segregation on the microstructure and phase in a / cobalt- based superalloy. Several samples were prepared from a cast alloy and homogenized at 1300 degrees C for different times, with a maximum of 24 h. A microstructural study of the cast alloy using wavelength-dispersive spectroscopic analysis revealed that elements such as Al, Ti, and Ni segregated mostly within interdendritic regions, whereas W atoms were segregated within dendrite cores. With an increase in homogenization time, segregation decreased and the initial dendritic structure was eliminated. Field-emission scanning electron microscopy micrographs showed that the phases in the cores and interdendritic regions of the as-cast alloy were 392 and 124 nm, respectively. The size difference of was found to be due to the different segregation behaviors of constituent elements during solidification. After homogenization, particularly after 16 h, segregation decreased; thus, the size, chemical composition, and hardness of the precipitated phase was mostly uniform throughout the samples.
OI Arabi, Hossein/0000-0003-3110-4198; ebrahimi,
gholamreza/0000-0003-2549-3246
SN 1674-4799
EI 1869-103X
PD FEB
PY 2019
VL 26
IS 2
BP 222
EP 233
DI 10.1007/s12613-019-1727-7
UT WOS:000458436000010
ER
PT J
AU Sauza, DJ
Dunand, DC
Noebe, RD
Seidman, DN
AF Sauza, Daniel J.
Dunand, David C.
Noebe, Ronald D.
Seidman, David N.
TI gamma '-(L1(2)) precipitate evolution during isothermal aging of a
Co-Al-W-Ni superalloy
SO ACTA MATERIALIA
AB The coarsening kinetics and elemental partitioning behavior of gamma'-(L1(2)) precipitates in a gamma(f.c.c.)-matrix for a model quaternary Co-8.8Al-8.9W-9.9Ni at.% superalloy are investigated utilizing isothermal aging conditions at 650, 800 and 900 degrees C. The gamma'-precipitate mean radius, number density, and volume fraction, at 800 and 900 degrees C, were studied using scanning electron microscopy; the calculated temporal exponents associated with coarsening of gamma'-precipitates display good agreement with model predictions for quasi stationary coarsening. An atom probe tomographic (APT) investigation of the aged gamma/gamma' microstructure at 650 degrees C demonstrates that the compositions and volume fractions of both phases vary continuously up to 4096 h. The aged microstructure at 650 degrees C consists of interconnected nanoscale gamma'-precipitates, corroborated utilizing SEM for the 4096 h aged-specimen. The activation energy for coarsening is estimated for the temperature range 650-900 degrees C to be 283 kJ mol(-1), in reasonable agreement with activation energies for diffusion of Al, W, and Ni in Co, suggesting that coarsening of gamma'-precipitates is limited by bulk-diffusion. APT measurements of specimens aged for 1024 hat 800 and 900 degrees C demonstrate that the isothermal aging temperature has a significant effect on the compositions and partitioning behavior of Co, Al, W and Ni between the gamma- and gamma'-phases. The partitioning ratio of the concentrations between the gamma'- and gamma-phases is largest for W, decreasing linearly from 5.3 +/- 0.1 at 650 degrees C to 2.1 +/- 1.2 at 900 degrees C, and smallest for Co, decreasing from 0.86 +/- 0.01 at 650 degrees C to 0.73 +/- 0.01 at 900 degrees C. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Dunand, David C/B-7515-2009; Seidman, David/B-6697-2009
SN 1359-6454
EI 1873-2453
PD FEB 1
PY 2019
VL 164
BP 654
EP 662
DI 10.1016/j.actamat.2018.11.014
UT WOS:000456902800056
ER
PT J
AU Bocchini, PJ
Sudbrack, CK
Noebe, RD
Seidman, DN
AF Bocchini, Peter J.
Sudbrack, Chantal K.
Noebe, Ronald D.
Seidman, David N.
TI Temporal evolution of a model Co-Al-W superalloy aged at 650 degrees C
and 750 degrees C
SO ACTA MATERIALIA
AB The temporal evolution of a gamma(f.c.c.)/gamma' (L1(2)) Co-8.8Al-73 W superalloy aged at 650 degrees C (10 min-4096 h) and 750 degrees C (10 min-256 h) is studied utilizing atom-probe tomography (APT), scanning electron microscopy, and Vickers microhardness testing. The evolution of the phase compositions, gamma' (L1(2)) volume fraction, and mean precipitate radius, <R2-D(t)>, are determined. Coarsening rate constants and temporal exponents are calculated for <R-D(t)> of the gamma' (L1(2))-nanoprecipitates. The temporal exponents are found to be generally close to 1/p = 1/3 as required for diffusion-limited coarsening. Tungsten solid-solubility is significantly reduced in the gamma(f.c.c.)-matrix at 650 degrees C (0.54 +/- 0.04 at. %) and 750 degrees C (1.35 +/- 0.06 at. %) when compared with aging at 900 degrees C (5.5 at. %). The value of <R-2D(t)> of the gamma' (L1(2))-nanoprecipitates increases with increasing aging time corresponding to an increase in the Vickers microhardness; the peak strength was not, however, achieved for the aging times investigated. The morphology of the gamma' (L1(2))-nanoprecipitates begins as spheroids but transitions to cuboids at longer aging times, with final the gamma' (L1(2)) volume fractions for aging at 650 degrees C and 750 degrees C being phi = 53% and 54%, respectively. The effect of quench-rate (either furnace-cooled, air-cooled, oil quenched, or water quenched) from a supersolvus temperature of 1050 degrees C on the microstructure of the alloy is also investigated. Slow cooling (furnace and air-cooling) is shown to result in a uniform distribution of nanometer sized gamma' (L1(2))-nanoprecipitates, unlike Ni-based superalloys in which the gamma' (L1(2))-nanoprecipitates form in a non-uniform or multimodal distribution. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Seidman, David/B-6697-2009
SN 1359-6454
EI 1873-2453
PD OCT 15
PY 2018
VL 159
BP 197
EP 208
DI 10.1016/j.actamat.2018.08.014
UT WOS:000445986300018
ER
PT J
AU Ozgun, O
Dinler, I
AF Ozgun, Ozgur
Dinler, Ilyas
TI Production and Characterization of WC-Reinforced Co-Based Superalloy
Matrix Composites
SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND
MATERIALS SCIENCE
AB Cobalt-based superalloy matrix composite materials were produced through the powder metallurgy technique using element powders at high purity and nano-sized wolfram carbide (WC) reinforcement in this study. An alloy that had the same chemical composition as the Stellite 6 alloy but not containing carbon was selected as the matrix alloy. The powder mixtures obtained as a result of mixing WC reinforcing member and element powders at the determined ratio were shaped by applying 300 MPa of pressure. The green components were sintered under argon atmosphere at 1240 A degrees C for 120 minutes. The densities of the sintered components were determined by the Archimedes' principle. Microstructural characterization was performed via X-ray diffraction analysis, scanning electron microscope examinations, and energy-dispersive spectrometry. Hardness measurements and tensile tests were performed for determining mechanical characteristics. The relative density values of the sintered components increased by increasing the WC reinforcement ratio and they could almost reach the theoretical density. It was determined from the microstructural examinations that the composite materials consisted of fine and equiaxed grains and coarse carbides demonstrating a homogeneous dispersion along the microstructure at the grain boundaries. As it was the case in the density values, the hardness and strength values of the composites increased by increasing the WC ratio.
SN 1073-5623
EI 1543-1940
PD JUL
PY 2018
VL 49A
IS 7
BP 2977
EP 2989
DI 10.1007/s11661-018-4640-1
UT WOS:000433974400036
ER
PT J
AU Tirado, FLR
Toinin, JP
Dunand, DC
AF Tirado, Fernando L. Reyes
Toinin, Jacques Perrin
Dunand, David C.
TI gamma plus gamma ' microstructures in the Co-Ta-V and Co-Nb-V ternary
systems
SO ACTA MATERIALIA
AB The Co-Ta-V and Co-Nb-V ternary systems are investigated in a search for L1(2)-ordered gamma' precipitation, based on recent computational predictions of stable gamma+gamma' microstructures. Four alloys with nominal (at. %) composition Co-6Ta-6V, Co-5.4Ta-6.6V-xNi (x = 0 and 10), and Co-6Nb-6V are arc-melted, homogenized at 1250 degrees C, and aged at 900 degrees C for 2,16 and 64 h. Nanometric, cuboidal gamma' precipitates within a fcc-gamma matrix are discovered in the Co-Ta-V system after aging for 2 h, and in the Co-Nb-V system after cooling from homogenization. The compositions of these two new gamma'-phases, as measured via atom probe tomography, are Co-3(Ta0.76V0.24) and Co-3(Nb0.65V0.35), respectively. Upon aging at 900 degrees C, the gamma' precipitates coarsen, dissolve and transform to lamellar C36-Co-3(Ta,V) and needle-shape DO19-CO3(Nb,V), measured as Co-3(Nb0.81V0.19) by APT, respectively. This shows that these ternary gamma' phases are metastable and points to the need for their stabilization via additional alloying elements. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Dunand, David C/B-7515-2009
OI Reyes Tirado, Fernando/0000-0003-4594-6185
SN 1359-6454
EI 1873-2453
PD JUN 1
PY 2018
VL 151
BP 137
EP 148
DI 10.1016/j.actamat.2018.03.057
UT WOS:000432760300013
ER
PT J
AU Weiser, M
Eggeler, YM
Spiecker, E
Virtanen, S
AF Weiser, Martin
Eggeler, Yolita M.
Spiecker, Erdmann
Virtanen, Sannakaisa
TI Early stages of scale formation during oxidation of gamma/gamma'
strengthened single crystal ternary Co-base superalloy at 900 degrees C
SO CORROSION SCIENCE
AB A study on the individual role of gamma and gamma'-phase during the scale formation on Co-9Al-9W (at.%) at 900 degrees C was conducted. High-accuracy thermogravimetric analysis was used to locate changes in the kinetics of scale growth. Compositions of three separated layers within the scale have been elucidated in detail. The results demonstrate the substantial impact of the two-phase microstructure on the initiation of oxidation for the appearance of the scale. Examination of STEM-EDX elemental mappings of the internal oxidation front during the early stages of scale growth can explain the origin of isolated Al2O3 precipitates instead of a closed protective layer.
RI Virtanen, Sannakaisa/N-3699-2015
OI Virtanen, Sannakaisa/0000-0002-7179-7593; Weiser,
Martin/0000-0002-9448-5787
SN 0010-938X
EI 1879-0496
PD MAY 1
PY 2018
VL 135
BP 78
EP 86
DI 10.1016/j.corsci.2018.02.020
UT WOS:000429513700007
ER
PT J
AU Chang, YJ
Yeh, AC
AF Chang, Yao-Jen
Yeh, An-Chou
TI The formation of cellular precipitate and its effect on the tensile
properties of a precipitation strengthened high entropy alloy
SO MATERIALS CHEMISTRY AND PHYSICS
AB In this work, a precipitation strengthened high entropy alloy was subjected to thermo-mechanical process in order to homogenize the grain microstructure. Tensile tests from room temperature to 1000 degrees C were conducted; microstructures were observed by scanning electron microscope and transmission electron microscope. Formation of cellular precipitate along grain boundaries was observed and could be related to hot tensile ductility drop at 750 degrees C (1023 K). Experimental analysis has indicated that driving force for the formation of cellular precipitates could be resulted from the chemical instability of supersaturation after annealing and migration of grain boundaries, and this phenomenon could be suppressed either through alloy design to increase gamma-prime solvus, and to hinder the migration of grain boundaries. This study serves as a guideline to design composition and thermo-mechanical process for precipitation strengthened high entropy alloys. (C) 2017 Elsevier B.V. All rights reserved.
SN 0254-0584
EI 1879-3312
PD MAY 1
PY 2018
VL 210
SI SI
BP 111
EP 119
DI 10.1016/j.matchemphys.2017.09.057
UT WOS:000429762200016
ER
PT J
AU Zhang, K
Liu, JL
Bao, BB
Xu, H
AF Zhang, Kai
Liu, Jinglei
Bao, Binbin
Xu, Hong
TI A novel spinel coating on cobalt-based Superalloy GH605 via an in-situ
oxidation approach
SO SURFACE AND INTERFACE ANALYSIS
AB Cr-Mn-O spinel coating was prepared on the surface of cobalt-based superalloy GH605 via an in-situ oxidation method in H2O-H-2 environment. The composition, morphology, and chemical value state of the oxide spinel coatings were investigated by SEM, EDS, XRD, Raman spectra, and XPS. It indicated that the morphology of coating varied with oxidation temperature, and granular surface appeared when oxidation temperature increased to 1100 degrees C. The formed Cr-Mn-O spinel coating was composed of Cr2O3 and MnCr2O4, and the thickness increased significantly with oxidation temperature. In the coating, Cr element existed in the state of Cr3+ ions and Cr6+ ions, while Mn element only existed in the form of Mn2+ ions.
SN 0142-2421
EI 1096-9918
PD APR
PY 2018
VL 50
IS 4
BP 448
EP 456
DI 10.1002/sia.6389
UT WOS:000427018800006
ER
PT J
AU Zhang, Y
Wang, Q
Dong, HG
Dong, C
Zhang, HY
Sun, XF
AF Zhang Yu
Wang Qing
Dong Honggang
Dong Chuang
Zhang Hongyu
Sun Xiaofeng
TI Nickel-Based Single-Crystal Superalloys (Ni, Co)-Al-(Ta, Ti)-(Cr, Mo, W)
Designed by Cluster-Plus-Glue-Atom Model and Their 1000 h Long-Term
Ageing Behavior at 900 degrees C
SO ACTA METALLURGICA SINICA
AB It has been pointed out recently that the compositions of industrial alloys are originated from cluster-plus-glue-atom structure units in solid solutions. Specifically for nickel-based superalloys, after properly grouping the alloying elements into Al, Ni-like ((Ni) over bar, including Ni, Co, Fe, Re, Ru and Ir), gamma '- forming Cr-like ((Cr) over bar (gamma '), including Ta, Ti, V, Nb), and gamma-forming Cr-like ((Cr) over bar;(gamma), including Cr, Mo and W), the optimal formula for single-crystal superalloys has been established [Al-(Ni) over bar (12)] (Al-1(Cr) over bar (gamma ')(0.5)(Cr) over bar (gamma)(1.5)). In this work, the first generation single-crystal superalloys were investigated on the basis of the proposed formula, by using (Ni) over bar=(Ni and Co), (Cr) over bar (gamma ')=(Ta and Ti), and (Cr) over bar (gamma)=(Cr, Mo and W). Two series of alloys were designed, formulated respectively as group A: [Al-Ni11Co1] (Al1TaxTi0.5-xCr1W0.25Mo0.25), with x=0, 0.25 and 0.5 (the corresponding mass fractions of Ta and Ti are respectively 0Ta-2.65Ti, 4.82Ta-1.26Ti and 9,32Ta-0Ti), and group B: [Al-Ni12-yCo gamma](Al1Ta0.25Ti0.25Cr1W0.25MO0.25), with y=1.5, 1.75, 2 and 2.5 (the corresponding mass fractions of Co are respectively 9.43Co, 11Co, 12.57Co and 15.71Co). The single-crystal superalloys were prepared using selector technique. And then they underwent the following tests of incipient melting, standard heat treatment and 1000 h long term ageing at 900 degrees C. It is found that: (1) In group A, with increasing Ta content (decreasing Ti), all the incipient melting temperatures are increased to above 1330 degrees C, and to the highest value is between 1335 degrees C and 1340 degrees C for alloy 9.32Ta-0Ti; the gamma(')gamma(') lattice negative misfits after standard heat treatment are reduced from -0.262% (0Ta-2.65Ti) to -0.247% (9.32Ta-0Ti); the gamma(') coarsening tendency after long-term ageing is deduced, and alloy 9.32Ta-0Ti has the lowest coarsening rate (K=5.6x10(-5) mu(3)/h). (2) In group B, the Co content does not influence the incipient melting temperature (always above 1330 degrees C) and the coarsening rate of gamma(') after long-term ageing. The major role of Co is to increase the mean size of the gamma(') precipitates to about 0.55 pm and the gamma(') volume fraction to about 69% after the standard heat treatment. These two groups of alloys have their gamma(') coarsening rates approaching the level of third-generation single-crystal superalloys (K approximate to(2.08 similar to 3.82)*10(-5) mu m(3)/h).
SN 0412-1961
PD APR
PY 2018
VL 54
IS 4
BP 591
EP 602
DI 10.11900/0412.1961.2017.00334
UT WOS:000433006500013
ER
PT J
AU Chen, XY
Li, YX
Huang, L
Zou, D
Wu, EX
Liu, YJ
Xie, YY
Yao, R
Liao, SY
Wang, GR
Zheng, F
AF Chen, Xiaoyu
Li, Yongxia
Huang, Lan
Zou, Dan
Wu, Enxi
Liu, Yanjun
Xie, Yuanyan
Yao, Rui
Liao, Songyi
Wang, Guangrong
Zheng, Feng
TI Effects of Precipitant and pH on Coprecipitation of Nanosized Co-Cr-V
Alloy Powders
SO MATERIALS
AB Nanosized Co-Cr-V alloy powders were synthesized via coprecipitation method. Effects of precipitants ((NH4)(2)C2O4<bold>H</bold>2O and Na2CO3) and pH were investigated by X-ray diffraction (XRD), Zeta potential analyzer, thermogravimetry-differential scanning calorimetry (TG-DSC), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). Co-Cr-V alloy powders were consisted of major face-centered cubic Co (fcc Co) and minor hexagonal close-packed Co (hcp Co). Grain sizes of precursors and Co-Cr-V alloy powders were increased with pH value (7-10) within the ranges of 3 similar to 39 and 39 similar to 66 nm, respectively. Rod-like or granular Co-Cr-V alloy particles were assembled by interconnected nanograins. At pH = 7, Na2CO3 precipitant was found to be beneficial to maintain the desirable composition of Co-Cr-V powders. It was also found that lower pH favors the maintenance of pre-designed composition, while grain coarsens at higher pH. Effects of variation for precipitant and pH on the morphology and composition of Co-Cr-V alloy powder were discussed in detail and relevant mechanism was further proposed.
OI Zheng, Feng/0000-0003-1807-7949
SN 1996-1944
PD OCT
PY 2017
VL 10
IS 10
AR 1108
DI 10.3390/ma10101108
UT WOS:000414639000003
ER
PT J
AU Bocchini, PJ
Sudbrack, CK
Noebe, RD
Dunand, DC
Seidman, DN
AF Bocchini, Peter J.
Sudbrack, Chantal K.
Noebe, Ronald D.
Dunand, David C.
Seidman, David N.
TI Effects of titanium substitutions for aluminum and tungsten in
Co-10Ni-9Al-9W (at%) superalloys
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
AB Polycrystalline Co-10Ni-(9 - x)Al-(9 - x)W-2xTi at% (x = 0, 1, 2, 3, 4) alloys with gamma(f.c.c.) plus gamma'(L1(2)) microstructures are investigated, where the gamma'(L1(2))-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal gamma'(L1(2))-precipitates grow and develop a rounded morphology. After 256 h of aging at 1000 degrees C, the precipitates in the 6 and 8 at% Ti alloys coalesce and develop an irregular, elongated morphology. After 1000 h of aging, replacement of W and Al with Ti increases both the mean radius, < R >, and volume fraction, phi, of the gamma'(L1(2))-phase from < R > = 463 nm and phi = 8% for 2 at% Ti to < R > = 722 nm and phi = 52% for 8 at% Ti. Composition measurements of the gamma(f.c.c.)-matrix and gamma'(L1(2))-precipitates demonstrate that Ti substitutes for W and Al in the gamma'(L1(2))-precipitates, increases the partitioning of W to gamma'(L1(2)), and changes the partitioning behavior of Al from a mild gamma'(L1(2))-former to a mild gamma(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely mu(Co7W6)-type, which do not destabilize the gamma(f.c.c.) plus gamma'(L1(2)) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys' mass density decrease; (ii) the gamma'(L1(2))-solvus temperature increases; (iii) the gamma'(L1(2)) volume fraction formed during aging at 1273 K (1000 degrees C) increases; and (iv) the 0.2% offset flow stress increases.
RI Dunand, David C/B-7515-2009; Seidman, David/B-6697-2009
SN 0921-5093
EI 1873-4936
PD SEP 29
PY 2017
VL 705
BP 122
EP 132
DI 10.1016/j.msea.2017.08.034
UT WOS:000413135700016
ER
PT J
AU Xu, YT
Xia, RL
Sha, QZ
Xia, TD
AF Xu Yangtao
Xia Rongli
Sha Qizhen
Xia Tiandong
TI Phase Composition and Cracking Behavior on TIG Cladding Layer of
Co-8.8Al-9.8W-0.2B Superalloy Based on JMatPro Software
SO RARE METAL MATERIALS AND ENGINEERING
AB Co-Al-W superalloy is a novel cobalt-based superalloy with the precipitation strengthening phase of ternary compound gamma-Co-3(Al,W). In order to study the cracking behavior of Co-8.8A1-9.8W-0.2B cladding layer on 304 stainless steel with TIG welding, the phase composition and relative contents at different positions of the cladding layer were investigated by thermodynamic simulation calculation of JMatPro software and experimental verification. The results show that the phase composition is the same at different positions of the cladding layer, but the content of those phases are not alike. Combining phase composition and contents of the cladding layer, the surface cracks of cladding layer are mainly hot cracks, which come from the integrated effect of the thermal stress, the phase transformation stress and the Laves phase.
SN 1002-185X
PD SEP
PY 2017
VL 46
IS 9
BP 2459
EP 2464
UT WOS:000435226100022
ER
PT J
AU Coakley, J
Lass, EA
Ma, D
Frost, M
Stone, HJ
Seidman, DN
Dunand, DC
AF Coakley, James
Lass, Eric A.
Ma, Dong
Frost, Matthew
Stone, Howard J.
Seidman, David N.
Dunand, David C.
TI Lattice parameter misfit evolution during creep of a cobalt-based
superalloy single crystal with cuboidal and rafted gamma-prime
microstructures
SO ACTA MATERIALIA
AB A [h00] oriented Co-based superalloy single crystal was crept under tension at 940 degrees C/100 MPa, resulting in a P-type raft morphology with extensive particle coalescence along the [h00] loading direction. However, particle coalescence was also observed in two perpendicular directions on the (h00) plane, normal to the loading axis. Tensile creep experiments were performed with in-situ neutron diffraction at 800 degrees C/500 MPa on this initially rafted gamma' microstructure, and for comparison at (i) 900 degrees C/260 MPa, and at (ii) 750 degrees C/875 MPa, both with initially cuboidal gamma' microstructures. The alloy was shown to exhibit a positive lattice parameter misfit, and during the first hour of creep at 900 degrees C/260 MPa, the lattice parameter evolution indicated changes in phase composition associated with gamma' dissolution as the alloy achieved phase equilibrium at 900 degrees C. For all three in-situ creep measurements, there was a significant divergence of the gamma' and gamma lattice parameters as creep proceeded. The lattice parameter misfit values between the precipitates and the matrix approached their unconstrained values during creep, and were notably large compared to those of Ni-based superalloys. This is indicative of a loss of coherency at the precipitate/matrix interfaces. Such a loss of coherency at the precipitate/matrix interfaces will likely degrade certain mechanical properties such as fatigue resistance, as has been shown for the Ni-based superalloys. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Ma, Dong/G-5198-2011; Dunand, David C/B-7515-2009; Seidman,
David/B-6697-2009; Lass, Eric/AAE-9593-2019
OI Ma, Dong/0000-0003-3154-2454; Lass, Eric/0000-0003-1428-3585; Frost,
Matthew/0000-0001-6821-170X; Coakley, James/0000-0001-8721-0438
SN 1359-6454
EI 1873-2453
PD SEP 1
PY 2017
VL 136
BP 118
EP 125
DI 10.1016/j.actamat.2017.06.025
UT WOS:000407665300011
ER
PT J
AU Bocchini, PJ
Sudbrack, CK
Sauza, DJ
Noebe, RD
Seidman, DN
Dunand, DC
AF Bocchini, Peter J.
Sudbrack, Chantal K.
Sauza, Daniel J.
Noebe, Ronald D.
Seidman, David N.
Dunand, David C.
TI Effect of tungsten concentration on microstructures of
Co-10Ni-6Al-(0,2,4,6) W-6Ti (at%) cobalt-based superalloys
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
AB The effects of reducing the W concentration (and concomitantly mass density) of Co-10Ni-6A1-xW-6Ti at% Co-based superalloys, with a gamma(f.c.c.) plus gamma'(L1(2)) microstructure, is investigated for a series of alloys with W concentrations of 6 at% (baseline alloy), 4 and 2 at% (W-reduced) and 0 at% (W-free). The gamma'(L1(2)) solvus temperature decreases strongly (by 46 degrees C per 1 at% reduction in W), while the liquidus and solvus temperatures decrease mildly (3-5 degrees C per 1 at% W reduction) as measured by differential scanning calorimetry. Scanning electron microscopy was used to image phase formation in all alloys. When aging at 900 or 1000 degrees C for 256 h, the W reduction does not result in the appearance of additional phases within the grains beyond the gamma(f.c.c.) and gamma'(L1(2)) phases present in the original alloy. Grain-boundary precipitates are present for all alloy compositions: W-rich or W-free precipitates after aging at 1000 degrees C, and coarsened gamma'(L1(2)) precipitates after aging at 900 degrees C. The composition of grain boundary precipitates were measured with energy-dispersive X-ray spectroscopy. Vickers microhardness values decrease with decreasing W content, due to a reduction in gamma'(L1(2)) precipitation and 'reduced solid-solution strengthening.
RI Seidman, David/B-6697-2009; Dunand, David C/B-7515-2009
SN 0921-5093
EI 1873-4936
PD JUL 17
PY 2017
VL 700
BP 481
EP 486
DI 10.1016/j.msea.2017.06.018
UT WOS:000406564300055
ER
PT J
AU Houdkova, S
Pala, Z
Smazalova, E
Vostfak, M
Cesanek, Z
AF Houdkova, Sarka
Pala, Zdenek
Smazalova, Eva
Vostfak, Marek
Cesanek, Zdenek
TI Microstructure and sliding wear properties of HVOF sprayed, laser
remelted and laser clad Stellite 6 coatings
SO SURFACE & COATINGS TECHNOLOGY
CT 7th International Meeting on Thermal Spraying (RIPT)
CY DEC 09-11, 2015
CL Limoges, FRANCE
AB The microstructure and sliding wear, properties of Co-Cr-W alloy (Stellite 6) coatings were studied in the dependence on the deposition technology. The HVOF as-sprayed, laser remelted HVOF sprayed and laser clad coatings were evaluated by SEM, XRD and ASTM G-133 reciprocating sliding wear test. In dependence on used deposition technology, the microstructure of coating varied namely in terms of grain size and phase composition. The XRD analyses in the wear track revealed that the strain-induced fcc-to-hcp transformation is taking part during wear of laser remelted HVOF sprayed coatings. The difference of the phase composition, grain size and strain-induced fcc-to-hcp transformation was shown to be responsible for differences in the sliding wear behaviour. (C) 2016 Elsevier B.V. All rights reserved.
RI Vostrak, Marek/C-1702-2016; Houdkova, Sarka/C-1244-2016; Pala,
Zdenek/C-8304-2014
OI Vostrak, Marek/0000-0003-4159-5664; Houdkova, Sarka/0000-0002-7354-3888;
Pala, Zdenek/0000-0002-5849-3018
SN 0257-8972
PD MAY 25
PY 2017
VL 318
BP 129
EP 141
DI 10.1016/j.surfcoat.2016.09.012
UT WOS:000402356100016
ER
PT J
AU Viat, A
Dreano, A
Fouvry, S
Bouchet, MID
Henne, JF
AF Viat, Ariane
Dreano, Alixe
Fouvry, Siegfried
Bouchet, Maria-Isabel De Barros
Henne, Jean-Francois
TI Fretting wear of pure cobalt chromium and nickel to identify the
distinct roles of HS25 alloying elements in high temperature glaze layer
formation
SO WEAR
AB HS25 cobalt-based superalloy was investigated between 100 and 600 degrees C under fretting wear (small amplitude reciprocating displacements) in a cross-cylinder contact. Tribological behavior was compared to pure cobalt, chromium and nickel tested under the same conditions and analyzed in terms of friction, wear, interface morphology and chemical composition by SEM-EDX and Raman spectroscopy. On HS25, the tribological tests resulted in the formation of a "glaze layer" of ground and compacted wear debris, which was protective against severe wear and high friction above 250 degrees C. Similar glaze layers were found for cobalt-cobalt (Co//Co) contacts, suggesting the determining role of cobalt in glaze layer formation whereas worn Cr//Cr and Ni//Ni interfaces exhibited poorly sintered debris and respectively adhesive and abrasive wear. To identify the role of alloying elements in glaze layer formation, the oxides formed in the interface were studied in terms of composition and thermal stability. As sintering appears to be a determining factor in glaze layer formation, the diffusion properties of cobalt and its oxides are emphasized. The strengthening and corrosion resistance properties of chromium and nickel in the alloy are also discussed. (C) 2017 Elsevier B.V. All rights reserved.
OI Dreano, Alixe/0000-0002-9221-7703
SN 0043-1648
EI 1873-2577
PD APR 15
PY 2017
VL 376
BP 1043
EP 1054
DI 10.1016/j.wear.2017.01.049
PN B
UT WOS:000403902000015
ER
PT J
AU Sumner, J
Potter, A
Simms, NJ
Oakey, JE
AF Sumner, J.
Potter, A.
Simms, N. J.
Oakey, J. E.
TI Modeling gas turbine materials' hot corrosion degradation in combustion
environments from H-2-rich syngas
SO MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION
AB Components of gas turbines (such as blades, vanes, combustor cans) exposed to combustion environments at high temperature are susceptible to hot corrosion attack. To successfully plan maintenance and to determine whether to operate in novel combustion modes (e.g., in integrated gasification combined cycles that incorporate pre-combustion carbon capture) predictions of hot corrosion component life must be made. In this paper, hot corrosion datasets relating to two alloys, MarM 509 (a cobalt-based superalloy), and Rene 80 (a nickel-based superalloy) form the basis of hot corrosion predictive lifetime models. The model framework is based on the two stages of incubation and propagation, with the transitions from incubation to propagation around the samples being based on Weibull statistics. The impact of a range of temperatures (including 700 and 900 degrees C), gas compositions (simulating the combustion of natural gas, H-2-rich syngas, or partially cleaned syngas), and deposit chemistries/fluxes have been assessed. Predictions have been made including the expected damage spread for a range of different exposure conditions.
OI Sumner, Joy/0000-0001-5435-200X
SN 0947-5117
EI 1521-4176
PD FEB
PY 2017
VL 68
IS 2
BP 205
EP 214
DI 10.1002/maco.201508779
UT WOS:000394663600010
ER
PT J
AU Vacchieri, E
Costa, A
Roncallo, G
Cacciamani, G
AF Vacchieri, E.
Costa, A.
Roncallo, G.
Cacciamani, G.
TI Service induced fcc -> hcp martensitic transformation in a Co-based
superalloy
SO MATERIALS SCIENCE AND TECHNOLOGY
CT 9th International Charles Parsons Turbine and Generator Conference
CY SEP, 2015
CL Loughborough Univ, Loughborough, ENGLAND
HO Loughborough Univ
AB Co-based superalloy, ECY768, applied on gas turbine vanes, shows the presence of cracks after service. EBSD studies revealed hcp transformation in the base material near cracked regions. This phase arises from a martensitic transformation of fcc matrix and bestows high fragility. The phase transformation is related to temperature and loading distribution that characterises components in service. However, at the service temperatures, the hcp transformation is not expected for ECY768. An in-house thermodynamic database was developed using the Calphad approach and thermodynamic calculations were applied to the complicated alloy composition for phase stability range evaluation. Moreover, a testing campaign was planned to artificially create this martensitic transformation and to comprehend the influence of plastic strain on fcc-hcp transformation. The transformation mechanisms were understood and some methods were developed for hcp-phase removal through refurbishment heat treatment.
RI Cacciamani, Gabriele/A-9643-2013
OI Cacciamani, Gabriele/0000-0001-9686-277X; Vacchieri,
Erica/0000-0003-2726-6194
SN 0267-0836
EI 1743-2847
PY 2017
VL 33
IS 9
BP 1100
EP 1107
DI 10.1080/02670836.2016.1273866
UT WOS:000400195200009
ER
PT B
AU Cygan, R
Rokicki, P
AF Cygan, Rafal
Rokicki, Pawel
BE Gomes, JFS
Meguid, SA
TI CHEMICAL COMPOSITION AND METALLURGICAL PURITY OF IN 713C SUPERALLOY
EFFECT ON TECHNOLOGICAL PARAMETERS FOR PRODUCTION OF AIRCRAFT ENGINE
CRITICAL COMPONENTS
SO PROCEEDINGS OF THE 7TH INTERNATIONAL CONFERENCE ON MECHANICS AND
MATERIALS IN DESIGN (M2D2017)
CT 7th International Conference on Mechanics and Materials in Design (M2D)
CY JUN 11-15, 2017
CL Albufeira, PORTUGAL
SP Univ Porto, Fac Engn, Univ Toronto, Mech & Aerosp Design Lab, Univ Algarve, Inst Super Engn, Portuguese Assoc Expt Mech, European Soc Expt Mech, Amer Soc Expt Mech, Japanese Soc Mech Engn, Int Measurement Confederat, Assoc Francaise Mecanique, European Assoc Dynam Mat, Inst Ciencia & Inovacao Enga Mecanica & Enga Ind, Lab Biomecanica Porto, Fundacao Ciencia Technologia, ABREU, Profess Congress Organizer
AB Aircraft engines components, including high and low pressure turbine blades and vanes, made of nickel and cobalt based superalloys, during long-term operation, are exposed to mass forces at elevated temperatures as well as corrosive agents. These conditions cause very high quality requirements for castings, both in terms of dimensional requirements, surface condition, as well as micro- and macrostructure. Quality of supplied charge materials is of fundamental importance for quality of castings, as all the bad qualities of the alloy transform naturally to the casting.
BN 978-989-98832-7-7
PY 2017
BP 619
EP 626
UT WOS:000427886600109
ER
PT J
AU Lu, X
Miki, T
Nagasaka, T
AF Lu, Xin
Miki, Takahiro
Nagasaka, Tetsuya
TI Activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag and their
application to the recycling of Ni-Co-Fe-based end-of-life superalloys
via remelting
SO INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS
AB To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al2O3-SiO2 slag. The activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B = (%CaO)/(%SiO2) = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.
SN 1674-4799
EI 1869-103X
PD JAN
PY 2017
VL 24
IS 1
BP 25
EP 36
DI 10.1007/s12613-017-1375-8
UT WOS:000393034800004
ER
PT J
AU Liu, LF
Wu, SS
Dong, YB
Lu, SL
AF Liu, Longfei
Wu, Shusen
Dong, Yunbo
Lu, Shulin
TI Effects of alloyed Mn on oxidation behaviour of a Co-Ni-Cr-Fe alloy
between 1050 and 1250 degrees C
SO CORROSION SCIENCE
AB The effects of Mn content on the oxidation behaviour of a Co-base superalloy with compositions of Co-29Cr-21Ni-23Fe-2.2Nb-1.6Si-xMn (x=0, 0.5, 1, 2) (Co22 alloy for short, wt.%) have been studied. Isothermal oxidation behaviour was investigated, and it showed kinetics of the Mn-containing samples followed a two-stage parabolic law. In the absence of Mn, scales on Co22 alloys consisted mainly of Cr2O3 and SiO2, and small amounts of Fe-Cr, Ni-Cr spinel nodules formed on the surface. When Mn was added, a triple oxide layer could be observed, consisting of Mn-Cr spinel as outer layer, Cr2O3 as middle layer and SiO2 in the innermost layer. (C) 2015 Elsevier Ltd. All rights reserved.
SN 0010-938X
EI 1879-0496
PD MAR
PY 2016
VL 104
BP 236
EP 247
DI 10.1016/j.corsci.2015.12.016
UT WOS:000370457500024
ER
PT J
AU Yu, H
Ukai, S
Oono, N
Sasaki, T
AF Yu, Hao
Ukai, Shigeharu
Oono, Naoko
Sasaki, Taisuke
TI Microstructure characterization of Co-20Cr-(5,10)Al oxide dispersion
strengthened superalloys
SO MATERIALS CHARACTERIZATION
AB In order to develop Co-based oxide dispersion strengthened (ODS) superalloys with excellent mechanical properties and oxidation resistance at the temperature above 1000 degrees C, Co-20Cr-(5,10)Al ODS superalloys were designed and fabricated by mechanical alloying (MA), spark plasma sintering (SPS), hot rolling and the final annealing at 1200 degrees C. Two different phases were identified; the Co solid solution of a fcc structure, and the B2 phase highly enriched with Aluminum. Composition and volume fraction of both phases are almost consistent with the Co-Cr-Al ternary phase diagram computed with the Pandat software. Another coarse fcc phase with smaller content of oxide particles was also characterized. This phase was probably formed through an incipient melting at the initial stage of SPS process. Fine oxides particles are densely distributed inside both, the fcc solid solution and the B2 phase. Grain boundaries and phase boundaries are decorated with the oxide particles, which are beneficial to grains and phases stability at elevated temperature. The observed unique core-shell structure was characterized as Y2Hf7O17 type in a core and Y2Hf2O7 type at a periphery of the oxide particles. (C) 2015 Elsevier Inc. All rights reserved.
RI YU, Hao/H-7228-2018
SN 1044-5803
EI 1873-4189
PD FEB
PY 2016
VL 112
BP 188
EP 196
DI 10.1016/j.matchar.2015.12.027
UT WOS:000370109200023
ER
PT J
AU Houdkova, S
Smazalova, E
Pala, Z
AF Houdkova, Sarka
Smazalova, Eva
Pala, Zdenek
TI Effect of Heat Treatment on the Microstructure and Properties of
HVOF-Sprayed Co-Cr-W Coating
SO JOURNAL OF THERMAL SPRAY TECHNOLOGY
AB Co-Cr-W HVOF-sprayed protective coatings are used for their high oxidation and wear resistance. Apart from the oxidation resistance, the stability of their mechanical properties in relation to thermal loading is crucial with respect to the most common high-temperature application areas. This work is focused mainly on evaluation of the heat-induced changes in the phase composition and related mechanical properties. It was shown that the original powder, composed fully from face-centered cubic Co-based alloy, partly changes its phase composition during spraying to a hexagonal close-packed (hcp) structure. The annealing further increases the ratio of the hcp phase in the structure. The heat-induced phase changes are accompanied by an increase in the coatings' hardness and cohesion strength. The abrasive and adhesive wear behavior was evaluated. While the coatings' heat treatment had a positive effect on the coefficient of friction, the abrasive and adhesive wear resistance of annealed coating was lower compared to as-sprayed coating.
RI Houdkova, Sarka/C-1244-2016
OI Houdkova, Sarka/0000-0002-7354-3888
SN 1059-9630
EI 1544-1016
PD FEB
PY 2016
VL 25
IS 3
BP 546
EP 557
DI 10.1007/s11666-015-0365-5
UT WOS:000374269200015
ER
PT J
AU Makineni, SK
Samanta, A
Rojhirunsakool, T
Alam, T
Nithin, B
Singh, AK
Banerjee, R
Chattopadhyay, K
AF Makineni, S. K.
Samanta, A.
Rojhirunsakool, T.
Alam, T.
Nithin, B.
Singh, A. K.
Banerjee, R.
Chattopadhyay, K.
TI A new class of high strength high temperature Cobalt based gamma-gamma '
Co-Mo-Al alloys stabilized with Ta addition
SO ACTA MATERIALIA
AB The present paper reports a new class of Co based superalloys that has gamma-gamma' microstructure and exhibits much lower density compared to other commercially available Co superalloys including Co-Al-W based alloys. The basic composition is Co-10Al-5Mo (at%) with addition of 2 at% Ta for stabilization of gamma' phase. The gamma-gamma' microstructure evolves through solutionising and aging treatment. Using first principles calculations, we observe that Ta plays a crucial role in stabilizing gamma' phase. By addition of Ta in the basic stoichiometric composition Co-3(Al, Mo), the enthalpy of formation (Delta H-f) of L1(2) structure (gamma' phase) becomes more negative in comparison to DO19 structure. The All of the L12 structure becomes further more negative by the occupancy of Ni and Ti atoms in the lattice suggesting an increase in the stability of the gamma' precipitates. Among large number of alloys studied experimentally, the paper presents results of detailed investigations on Co-10Al-5Mo-2Ta, Co-30Ni-10Al-5Mo-2Ta and Co-30Ni-10Al-5Mo-2Ta-2Ti. To evaluate the role alloying elements, atom probe tomography investigations were carried out to obtain partition coefficients for the constituent elements. The results show strong partitioning of Ni, Al, Ta and Ti in ordered gamma' precipitates. 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Singh, Abhishek/C-2039-2009
OI Singh, Abhishek/0000-0002-7631-6744; Samanta, Atanu/0000-0001-7918-2772;
Makineni, Surendra/0000-0002-4493-6498
SN 1359-6454
EI 1873-2453
PD SEP 15
PY 2015
VL 97
BP 29
EP 40
DI 10.1016/j.actamat.2015.06.034
UT WOS:000359875800003
ER
PT J
AU Terberger, PJ
Sebold, D
Webler, R
Ziener, M
Neumeier, S
Klein, L
Virtanen, S
Goken, M
Vassen, R
AF Terberger, Philipp J.
Sebold, Doris
Webler, Ralf
Ziener, Marco
Neumeier, Steffen
Klein, Leonhard
Virtanen, Sannakaisa
Goeken, Mathias
Vassen, Robert
TI Isothermal aging of a gamma '-strengthened Co-Al-W alloy coated with
vacuum plasma-sprayed MCrAlY bond coats
SO SURFACE & COATINGS TECHNOLOGY
AB Cobalt-based superalloys with a gamma/gamma' microstructure were discovered in 2006 and are currently being investigated as an alternative to nickel-based superalloys for high-temperature, high-load applications in gas turbine blades. They promise a better castability combined with a similar creep strength. Superalloy turbine blades are commonly coated with oxidation resistant bond coats. For this reason their compatibility needs to be studied. Co-9Al-9W specimens with a gamma/gamma' microstructure were coated with either a nickel-based or cobalt-based MCrAlY bond coat using vacuum plasma spraying. After aging at 900 degrees C in air for up to 500 h no decomposition of the gamma' phase was found in the bulk superalloy. The interdiffusion zone shows several different W-rich topologically close-packed phases arising from the dissolution of the gamma' phase in this region. The W-rich phases are identified to be mu phase for both bond coats and R phase for the nickel-based bond coat only. Their total volume is higher for the nickel-based bond coat. Therefore the cobalt-based bond coat is better suited for the Co-based superalloy substrate. Room temperature hardness and Young's modulus were measured using nanoindentation in the initial state and after heat treatment. A significantly higher Young's modulus was found for the cobalt-based bond coat (C) 2015 Elsevier B.V. All rights reserved.
RI Neumeier, Steffen/F-7092-2017; Virtanen, Sannakaisa/N-3699-2015; Goken,
Mathias/F-7940-2015
OI Neumeier, Steffen/0000-0001-7853-0368; Virtanen,
Sannakaisa/0000-0002-7179-7593; Goken, Mathias/0000-0002-3226-0304
SN 0257-8972
PD AUG 25
PY 2015
VL 276
BP 360
EP 367
DI 10.1016/j.surfcoat.2015.06.048
UT WOS:000360594600045
ER
PT J
AU Tarasova, TV
Nazarov, AP
Prokof'ev, MV
AF Tarasova, T. V.
Nazarov, A. P.
Prokof'ev, M. V.
TI Effect of the regimes of selective laser melting on the structure and
physicomechanical properties of cobalt-base superalloys
SO PHYSICS OF METALS AND METALLOGRAPHY
AB In this article, we give a preferential regime of selective laser melting for the production of parts from a cobalt superalloy using a PTK-PS domestic machine, which can find application upon the production of components from various superalloys in the aviation and atomic industry and in the automobile industry. We have investigated the phase composition and determined the physicomechanical properties of the samples prepared under the preferential regime of selective laser melting. It has been established that the structure of the alloy obtained by selective laser melting consists of two supersaturated solid solutions based on the low-temperature hexagonal and high-temperature cubic cobalt modifications, which leads to an increase in the strength characteristics of the samples in comparison with the cast samples.
SN 0031-918X
EI 1555-6190
PD JUN
PY 2015
VL 116
IS 6
BP 601
EP 605
DI 10.1134/S0031918X15060101
UT WOS:000356378600010
ER
PT J
AU Makineni, SK
Nithin, B
Chattopadhyay, K
AF Makineni, S. K.
Nithin, B.
Chattopadhyay, K.
TI A new tungsten-free gamma-gamma ' Co-Al-Mo-Nb-based superalloy
SO SCRIPTA MATERIALIA
AB We present the first report of a tungsten-free cobalt-based superalloy having a composition Co-10Al-5Mo-2Nb. The alloy is strengthened by cuboidal precipitates of metastable Co-3(Al,Mo,Nb) distributed throughout the microstructure. The precipitates are coherent with the face-centred cubic gamma-Co matrix and possess ordered Ll(2) structure. The microstructure is identical to the popular gamma-gamma' type nickel-based superalloys and that of recently reported Co-Al-W-based alloys. Being tungsten free, the reported alloy has higher specific proof stress compared to existing cobalt-based superalloys. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
OI Makineni, Surendra/0000-0002-4493-6498
SN 1359-6462
PD MAR 15
PY 2015
VL 98
BP 36
EP 39
DI 10.1016/j.scriptamat.2014.11.009
UT WOS:000348965500010
ER
PT J
AU Makineni, SK
Nithin, B
Chattopadhyay, K
AF Makineni, S. K.
Nithin, B.
Chattopadhyay, K.
TI Synthesis of a new tungsten-free gamma-gamma ' cobalt-based superalloy
by tuning alloying additions
SO ACTA MATERIALIA
AB The paper presents the synthesis of a new class of gamma-gamma' cobalt-based superalloy that is free of tungsten as an alloying addition. It has much lower density and higher specific strength than the existing cobalt-based superalloys. The current superalloys have a base composition of Co-10Al and are further tuned by the addition of a binary combination of molybdenum and niobium, with the optimum composition of Co-10Al-5Mo-2Nb. The solvus temperature of the alloy (866 degrees C) can be further enhanced above 950 C by the addition of Ni to give the form Co-xNi-10Al-5Mo-2Nb, where x can be from 0 to 30 at.%. After heat treatment, these alloys exhibit a duplex microstructure with coherent cuboidal L1(2)-ordered precipitates (gamma') throughout the face-centred cubic matrix (gamma), yielding a microstructure that is very similar to nickel-based superalloys as well as recently developed Co-Al-W-based alloys. We show that the stability of the gamma' phase improves significantly with the nickel addition, which can be attributed to the increase in solvus temperature. A very high specific 0.2% proof stress of 94.3 MPa g(-1) cm(-3) at room temperature and 63.8 MPa g(-1) cm(-3) at 870 degrees C were obtained for alloy Co-30Ni-10Al-5Mo-2Nb. The remarkably high specific strength of these alloys makes this class of alloy a promising material for use at high temperature, including gas turbine applications. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
OI Makineni, Surendra/0000-0002-4493-6498
SN 1359-6454
EI 1873-2453
PD FEB 15
PY 2015
VL 85
BP 85
EP 94
DI 10.1016/j.actamat.2014.11.016
UT WOS:000348956800009
ER
PT J
AU Roa, JJ
Jimenez-Pique, E
Tarrago, JM
Zivcec, M
Broeckmann, C
Llanes, L
AF Roa, J. J.
Jimenez-Pique, E.
Tarrago, J. M.
Zivcec, M.
Broeckmann, C.
Llanes, L.
TI Berkovich nanoindentation and deformation mechanisms in a hardmetal
binder-like cobalt alloy
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
AB A cobalt-base solid solution is the most used binder for hardmetals (WC-Co cemented carbides) in a wide range of industrial applications. In the composite material such cobalt alloy is surrounded by hard carbides grains; thus, a direct evaluation of its intrinsic mechanical properties is not an easy task. In order to overcome this inconvenience, a model cobalt alloy with a composition similar to that exhibited by typical hardmetal binder (containing W and C in solid solution) was processed following a powder metallurgy route. Nanoindentation testing at different length scales has been performed to study the mechanical properties as well as to introduce plastic deformation in individual grains of the dilute face centered cubic (fcc) stabilized model Co-W-C alloy. It is found that it exhibits an isotropic mechanical response, without any evidence of indentation size effects. The main deformation mechanism activated during the indentation tests resulted to be deformation twinning, although combined with limited planar slip but with no evidence of stress-induced phase transformation. Such finding is related to the high W and C amounts dissolved in the model Co alloy studied, and its effect on stabilizing the fcc configuration and increasing the stacking fault energy. The effective use of small-length scale mechanical characterization protocols is finally discussed for understanding deformation response of binder-like alloys and optimizing microstructural design of hardmetals. (C) 2014 Elsevier B.V. All rights reserved.
RI ROA, JOAN JOSEP/K-1656-2015; Llanes, Luis/H-9761-2015
OI ROA, JOAN JOSEP/0000-0002-7440-0766; Llanes, Luis/0000-0003-1054-1073;
Jimenez-Pique, Emilio/0000-0002-6950-611X
SN 0921-5093
EI 1873-4936
PD JAN 5
PY 2015
VL 621
BP 128
EP 132
DI 10.1016/j.msea.2014.10.064
UT WOS:000347590600016
ER
PT J
AU Lass, EA
Williams, ME
Campbell, CE
Moon, KW
Kattner, UR
AF Lass, Eric A.
Williams, Maureen E.
Campbell, Carelyn E.
Moon, Kil-Won
Kattner, Ursula R.
TI gamma' Phase Stability and Phase Equilibrium in Ternary Co-Al-W at 900 A
degrees C
SO JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION
AB Phase equilibria at 900 A degrees C in the Co-rich Co-Al-W ternary system are investigated through isothermal annealing of six alloy compositions for times up to 8000 h. The volume fraction of the L1(2)-gamma' phase co-existing with disordered FCC-gamma, B2 and D0(19) phases is found to steadily decrease with increasing annealing time indicating that it is unstable at 900 A degrees C. Additional heat treatments at 850 and 1000 A degrees C further suggest it is a nonequilibrium phase at all temperatures in the ternary system. The L1(2)-gamma' phase dissolves slowly with significant amounts remaining in some alloys after 8000 h at 900 A degrees C. However, the present work clearly indicates the microstructure is moving toward a three-phase equilibrium between gamma, D0(19), and B2. The collected compositional and phase equilibria information provide much needed data for improving the available thermodynamic assessments of the ternary Co-Al-W alloy system.
RI Lass, Eric/AAE-9593-2019
OI Lass, Eric/0000-0003-1428-3585
SN 1547-7037
EI 1863-7345
PD DEC
PY 2014
VL 35
IS 6
BP 711
EP 723
DI 10.1007/s11669-014-0346-2
UT WOS:000345281500007
ER
PT J
AU Ren, W
Li, Q
Song, J
Xiao, C
Xu, Z
Cao, C
AF Ren, W.
Li, Q.
Song, J.
Xiao, C.
Xu, Z.
Cao, C.
TI Oxidation and microstructure evolution of cobalt aluminide coatings on
directionally solidified superalloys during long term exposure at 1000
degrees C
SO MATERIALS RESEARCH INNOVATIONS
AB Using low pressure chemical vapour deposition, cobalt aluminide coatings were deposited onto directionally solidified Ni based superalloys (DZ466 and DS GTD111). Isothermal oxidation testing of the coated specimens was performed at 1000 degrees C under atmospheric pressure for times up to 2500 h. Oxidation and interdiffusion behaviour of the coating superalloy systems was examined. It was observed that the oxide growth mode of both coating systems conformed to a staged parabolic law, with differences in the transient stage related to the growth of theta-Al2O3. Coating degradation and formation of chromium containing precipitates occurred during exposure because of severe interdiffusion between the coating and superalloy. The composition of the superalloy substrate played an important role in the microstructure evolution of the aluminide coating, and the corresponding mechanism is discussed.
SN 1432-8917