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Co_suoeralloys1.txt
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Co_suoeralloys1.txt
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FN Clarivate Analytics Web of Science
VR 1.0
PT J
AU Sato, J
Omori, T
Oikawa, K
Ohnuma, I
Kainuma, R
Ishida, K
AF Sato, J
Omori, T
Oikawa, K
Ohnuma, I
Kainuma, R
Ishida, K
TI Cobalt-base high-temperature alloys
SO SCIENCE
AB We have identified cobalt-base superalloys showing a high-temperature strength greater than those of conventional nickel-base superalloys. The cobalt-base alloys are strengthened by a ternary compound with the L1(2) structure, gamma ' Co-3( Al,W), which precipitates in the disordered gamma face-centered cubic cobalt matrix with high coherency and with high melting points. We also identified a ternary compound, gamma ' Ir-3(Al, W), with the L1(2) structure, which suggests that the Co-Ir-Al-W-base systems with gamma + gamma ' (Co, Ir)(3)(Al, W) structures offer great promise as candidates for next-generation high-temperature materials.
RI Kainuma, Ryosuke/I-6482-2013; Oikawa, Katsunari/C-6660-2009; OHNUMA,
Ikuo/J-4253-2015; Omori, Toshihiro/A-4478-2017
OI Oikawa, Katsunari/0000-0002-5269-8426; Omori,
Toshihiro/0000-0001-9174-0239
SN 0036-8075
EI 1095-9203
PD APR 7
PY 2006
VL 312
IS 5770
BP 90
EP 91
DI 10.1126/science.1121738
UT WOS:000236584400036
PM 16601187
ER
PT J
AU Moskal, G
Migas, D
Mikuskiewicz, M
Niemiec, D
Godzierz, M
AF Moskal, Grzegorz
Migas, Damian
Mikuskiewicz, Marta
Niemiec, Dawid
Godzierz, Marcin
TI Oxidation behavior of Co-Al-Mo-Nb and Co-Ni-Al-Mo-Nb new tungsten-free
gamma-gamma ' cobalt-based superalloys
SO OCHRONA PRZED KOROZJA
AB This paper presents the oxidation behavior of tungsten-free gamma-gamma' Co-10Al- 5Mo-2Nb and Co-20Ni-10Al-5Mo-2Nb cobalt-based superalloys. This type of alloys is an alternative materials for tungsten contains alloys of Co-Al-W type with gamma'-Co-3(Al.W) intermetallic phase adequate to gamma'-Ni3Al phase identified in Ni based superalloys. Applications of Mo and Nb as a replacement of W is related to tendency to lowering the density of alloys. The investigation included thermogravimetric studies up to 1200 degrees C. The oxidized layer was evaluated, therein microstructure, chemical and phase composition analyses were performed using various methods, inclusive of x-ray diffraction, SEM/EDS analysis and light microscopy.
RI Mikuskiewicz, Marta/G-7088-2011; Moskal, Grzegorz/AAC-9033-2019
OI Mikuskiewicz, Marta/0000-0002-1808-069X; Moskal,
Grzegorz/0000-0001-7396-6568
SN 0473-7733
EI 2449-9501
PD SEP
PY 2017
VL 60
IS 9
BP 318
EP 322
DI 10.15199/40.2017.9.5
UT WOS:000435646800006
ER
PT J
AU Migas, D
Moskal, G
Niemiec, D
AF Migas, Damian
Moskal, Grzegorz
Niemiec, Dawid
TI Surface Condition of New gamma-gamma ' Co-Al-Mo-Nb and Co-Al-W
Cobalt-Based Superalloys After Oxidation at 800 degrees C
SO JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
AB A new type gamma-gamma' Co-Al-Mo-Nb Co-based superalloys were developed due to limitations of basic Co-Al-W superalloys, related to tungsten alloying. The present study aims to characterization of new gamma-gamma' Co-10Al-5Mo-2Nb (at.%) cobalt-based superalloy performance in terms of the high-temperature exposure under cyclic conditions, with particular regard to surface condition. Specimens were tested in cycles of high-temperature exposition (25, 50, 75, 100 and 150 h) in air environment at 800 A degrees C. Detailed analysis of oxidized surfaces by scanning electron microscopy, energy-dispersive spectroscopy and x-ray diffraction was made at various intervals during testing. The cyclic oxidation behavior of new alloy was compared to the basic Co-9Al-9W (at.%) Co-based superalloy.
RI Moskal, Grzegorz/AAC-9033-2019
OI Moskal, Grzegorz/0000-0001-7396-6568; Migas, Damian/0000-0003-0328-964X
SN 1059-9495
EI 1544-1024
PD FEB
PY 2018
VL 27
IS 2
BP 447
EP 456
DI 10.1007/s11665-018-3127-y
UT WOS:000424305800012
ER
PT J
AU Neumeier, S
Freund, LP
Goken, M
AF Neumeier, S.
Freund, L. P.
Goeken, M.
TI Novel wrought gamma/gamma ' cobalt base superalloys with high strength
and improved oxidation resistance
SO SCRIPTA MATERIALIA
AB New polycrystalline Co-base superalloys with gamma/gamma' microstructure have been developed, which show excellent mechanical properties and enhanced oxidation behavior. The gamma' solvus temperature of these alloys is comparatively low giving a large processing window. The yield strength of these alloys is similar to that of wrought Ni-base superalloys. However, the creep strength at 750 degrees C is largely exceeding that of the Ni-base superalloys Waspaloy and Udimet 720Li. Oxidation tests indicate that the oxidation resistance is comparable to commercial Ni-base superalloys. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Goken, Mathias/F-7940-2015; Neumeier, Steffen/F-7092-2017
OI Goken, Mathias/0000-0002-3226-0304; Neumeier,
Steffen/0000-0001-7853-0368
SN 1359-6462
PD DEC
PY 2015
VL 109
BP 104
EP 107
DI 10.1016/j.scriptamat.2015.07.030
UT WOS:000361078100024
ER
PT J
AU Moskal, G
Migas, D
Niemiec, D
Tomaszewska, A
AF Moskal, Grzegorz
Migas, Damian
Niemiec, Dawid
Tomaszewska, Agnieszka
TI Thermogravimetric Investigations of Novel gamma-gamma ' Co-Al-W and
Co-Al-Mo-Nb Cobalt-Based Superalloys
SO JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME
AB Cobalt-based gamma-gamma' superalloys are novel heat-resistant materials suitable for high-temperature applications, such as components of the turbine engine. These alloys exhibit favorable strength and corrosion resistance at high temperatures owing to the gamma-gamma' microstructure, analogous to that of Ni-based superalloys. The aim of this paper is to evaluate the oxidation behavior of basic Co-9Al-9W (at%) and new tungsten-free Co-10Al-5Mo-2Nb (at%) alloys at elevated temperatures. The investigation is concerned with thermogravimetric studies in the temperature range of 40-1200 degrees C. The oxidized surfaces after high temperature oxidation have been characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction analysis (XRD).
SN 0094-4289
EI 1528-8889
PD OCT
PY 2019
VL 141
IS 4
AR 041008
DI 10.1115/1.4043626
UT WOS:000499948900008
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 Bian, HK
Xu, XD
Li, YP
Koizumi, Y
Wang, ZC
Chen, MW
Yamanaka, K
Chiba, A
AF Bian, Huakang
Xu, Xiandong
Li, Yunping
Koizumi, Yuichiro
Wang, Zhongchang
Chen, Mingwei
Yamanaka, Kenta
Chiba, Akihiko
TI Regulating the coarsening of the gamma ' phase in superalloys
SO NPG ASIA MATERIALS
AB The properties of superalloys are typically deteriorated by the coarsening of the nano-sized gamma' phase, which is the primary strengthening component at high temperatures. Stabilizing the gamma' phase represents one of the key challenges in developing next-generation superalloys. Herein, we fabricate a cobalt-nickel-based superalloy with a nanoscale coherent gamma' phase, (Ni,Co)(3) (Al, Ti, Nb), which is isolated by stacking-fault ribbons in the alloy matrix as a result of the Suzuki segregation of alloying atoms. Additionally, we demonstrate that this new nanostructure can slow down the coarsening of the gamma' phase at high temperatures. As a result, the cobalt-nickel-based superalloy displays considerably high tensile yield points, exceeding 1650 MPa at room temperature and 1250 MPa at 973 K, which are markedly higher than those of the commonly used nickel-and cobalt-based superalloys. This study thereby paves a new path for developing superalloys with exceptional mechanical performance and thermal stability.
RI Li, Yunping/M-2076-2016; Li, Yunping/A-8109-2011; Koizumi,
Yuichiro/C-2697-2011; Wang, Zhongchang/M-7124-2019; Yamanaka,
Kenta/G-4745-2014; Yamanaka, Kenta/J-5071-2019; Chen,
Mingwei/A-4855-2010
OI Li, Yunping/0000-0002-4657-2923; Koizumi, Yuichiro/0000-0001-7061-7135;
Yamanaka, Kenta/0000-0003-1675-4731; Yamanaka,
Kenta/0000-0003-1675-4731; Chen, Mingwei/0000-0002-8274-3099
SN 1884-4049
EI 1884-4057
PD AUG
PY 2015
VL 7
AR e212
DI 10.1038/am.2015.96
UT WOS:000360946000007
ER
PT J
AU Gu, YF
Cui, C
Ping, D
Harada, H
Fukuda, T
Fujioka, J
AF Gu, Y. F.
Cui, C.
Ping, D.
Harada, H.
Fukuda, T.
Fujioka, J.
TI Creep behavior of new kinds of Ni-Co-base superalloys
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
CT 11th International Conference of Creep and Fracture of Engineering
Materials and Structures
CY MAY 04-09, 2008
CL Bad Berneck, GERMANY
AB This paper concerns our recent work on developing a new kind of advanced disk alloys based on the mixtures of two kinds of two-phase superalloys, Co-base Co-16.9wt.%Ti and Ni-base U720Li superalloys, for the latest turbine design. The tensile creep behavior of these new Ni-Co-base superalloys at temperatures in the range of 650-760 degrees C and at initial applied stresses of 480-830 MPa were investigated. Comparing a new Ni-Co-base alloy (TMW-4) to U720Li by a Larson-Miller plot shows that a temperature gain in stress-rupture strength of 30 can be expected in a TMW alloy with fine-grained microstructure (10 (m). (C) 2009 Elsevier B.V. All rights reserved.
SN 0921-5093
EI 1873-4936
PD JUN 15
PY 2009
VL 510-11
SI SI
BP 250
EP 255
DI 10.1016/j.msea.2008.04.128
UT WOS:000266397800046
ER
PT J
AU Yao, CS
Chen, Z
Wang, YX
Zhang, J
Du, XJ
AF Yao Chuansheng
Chen Zheng
Wang Yongxin
Zhang Jing
Du Xiujuan
TI Research Progress in New Co-Based gamma-gamma ' High-Temperature Alloys
SO RARE METAL MATERIALS AND ENGINEERING
AB A brief overview of the research progress of new cobalt-based alloys containing ordered L1(2) precipitates gamma'-Co-3(Al, W) was presented. The emphasis was on the microstructure, composition segregation and high temperature behavior of the gamma-gamma' alloys with addition of different elements into ternary Co-Al-W system. The applications of new cobalt-based alloys were forecast and the research prospect required in future was pointed out.
SN 1002-185X
PD NOV
PY 2012
VL 41
IS 11
BP 2064
EP 2068
UT WOS:000312111900040
ER
PT J
AU Gu, Y
Harada, H
Cui, C
Ping, D
Sato, A
Fujioka, J
AF Gu, Y.
Harada, H.
Cui, C.
Ping, D.
Sato, A.
Fujioka, J.
TI New Ni-Co-base disk superalloys with higher strength and creep
resistance
SO SCRIPTA MATERIALIA
AB A new kind of Ni-Co-base superalloys with a gamma/gamma' two-phase structure has been proposed recently for turbine disk applications. Some of these Ni-Co-base superalloys are assessed by tensile tests. The results show that the Ni-Co-base alloys can be processed by cheap cast and wrought route and show superior tensile strength at temperatures up to 750 degrees C and higher creep resistances up to 725 degrees C than those of the UDIMET 720 LI alloy. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
SN 1359-6462
PD NOV
PY 2006
VL 55
IS 9
BP 815
EP 818
DI 10.1016/j.scriptamat.2006.07.008
UT WOS:000240693700016
ER
PT J
AU Yu, H
Ukai, S
Hayashi, S
Oono, N
AF Yu, Hao
Ukai, Shigeharu
Hayashi, Shigenari
Oono, Naoko
TI Effect of Cr on the Oxidation Resistance of Co-Based Oxide Dispersion
Strengthened Superalloys
SO MATERIALS TRANSACTIONS
AB Alumina-forming oxide dispersion strengthened (ODS) superalloys are favorable oxidation-resistant materials for extremely high temperature applications. In order to develop the advanced Co-based superalloys with high strength and superior oxidation resistance at elevated temperature of 1000 degrees C, a new series of Co-Cr-Al ODS superalloys were designed and fabricated by mechanical alloying (MA) and spark plasma sintering (SPS), and then followed by hot rolling and annealing at 1200 degrees C. In this work, the oxidation behavior of Co-10Al (mass%) ODS superalloys with/without 20Cr was investigated at 1000 degrees C in air to understand the effect of Cr on oxidation resistance. The results indicate that the addition of Cr improves the oxidation resistance significantly through optimizing the oxide scales from the multilevel scales with an external CoO/CoAl2O4 and an internal Al2O3 to a single layer of Al2O3. The alumina-forming Co-20Cr-10Al (mass%) ODS superalloys are expected to be applicable at 1000 degrees C.
SN 1345-9678
EI 1347-5320
PY 2018
VL 59
IS 4
BP 563
EP 567
DI 10.2320/matertrans.MJ201603
UT WOS:000428981000007
ER
PT J
AU Mukherji, D
Rosler, J
Strunz, P
Gilles, R
Schumacher, G
Piegert, S
AF Mukherji, Debashis
Roesler, Joachim
Strunz, Pavel
Gilles, Ralph
Schumacher, Gerhard
Piegert, Sebastian
TI Beyond Ni-based superalloys: Development of CoRe-based alloys for gas
turbine applications at very high temperatures
SO INTERNATIONAL JOURNAL OF MATERIALS RESEARCH
AB High temperature material development is mainly driven by gas turbine needs. Today, Ni-based superalloys are the dominant material class in the hot section of turbines. Material development will continue to push the maximum service temperature of Ni-superalloys upwards. However, this approach has a fundamental limit and cannot be sustained indefinitely, as the Ni-superalloys are already used very close to their melting point. Within the framework of a DFG Forschergruppe program (FOR 727) - "Beyond Ni-base Superalloys" - CoRe based alloys are being developed at the Technische Universitat Braunschweig as a new generation of high temperature materials that can be used at + 100 degrees C above single crystal Ni-superalloys. Two main strengthening concepts, namely precipitation hardening by MC carbides and composite hardening by Co(2)Re(3)-type phase are being explored in CoRe alloy development. Selected results of microstructural characterizations, including in-situ measurements by synchrotron and neutron scattering are presented.
RI Mukherji, Debashis/M-1646-2019; Strunz, Pavel/D-1610-2011
OI Mukherji, Debashis/0000-0001-6882-4709; Strunz,
Pavel/0000-0002-0829-4926
SN 1862-5282
PD SEP
PY 2011
VL 102
IS 9
BP 1125
EP 1132
DI 10.3139/146.110563
UT WOS:000296032900009
ER
PT J
AU Migas, D
Moskal, G
Mikuskiewicz, M
Maciag, T
AF Migas, Damian
Moskal, Grzegorz
Mikuskiewicz, Marta
Maciag, Tomasz
TI Thermogravimetric investigations of new gamma-gamma' cobalt-based
superalloys
SO JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
AB The aim of the study is characterization of high-temperature oxidation behavior of new Co-based superalloys by thermogravimetry (TG). The following alloys have been taken into account: Co-9Al-9W, Co-20-Ni-7Al-7W, Co-10Al-5Mo-2Nb and Co-20Ni-10Al-5Mo-2Nb (at.%). The thermogravimetric analysis was carried out in the temperature range 40-1200 degrees C of heating rate 5 degrees min(-1). The investigation was performed using the thermal analyzer NETZSCH STA 449 F3 Jupiter. TG-DTG plots showed oxidation behavior up to 1200 degrees C and indicated the temperatures of further isothermal oxidation examinations. The oxidation behavior of basic Co-9Al-9W (at.%) alloy was compared to W-free Co-10Al-5Mo-2Nb and Co-20Ni-10Al-5Mo-2Nb (at.%) alloys. The obtained data showed different oxidation behavior dependably on the type of alloying elements. Moreover, the effect of Ni addition on oxidation performance was determined. The scales grown on Co-base superalloys after thermogravimetry were evaluated by means of scanning electron microscopy and energy dispersive spectroscopy.
RI Moskal, Grzegorz/AAC-9033-2019; Mikuskiewicz, Marta/M-3710-2019
OI Moskal, Grzegorz/0000-0001-7396-6568; Mikuskiewicz,
Marta/0000-0002-1808-069X; Migas, Damian/0000-0003-0328-964X; Maciag,
Tomasz/0000-0002-8974-2478
SN 1388-6150
EI 1588-2926
PD OCT
PY 2018
VL 134
IS 1
BP 119
EP 125
DI 10.1007/s10973-018-7420-7
UT WOS:000444736600013
ER
PT J
AU Liu, XJ
Pan, YW
Chen, YC
Han, JJ
Yang, SY
Ruan, JJ
Wang, CP
Yang, YS
Li, YJ
AF Liu, Xingjun
Pan, Yunwei
Chen, Yuechao
Han, Jiajia
Yang, Shuiyuan
Ruan, Jingjing
Wang, Cuiping
Yang, Yuansheng
Li, Yingju
TI Effects of Nb and W Additions on the Microstructures and Mechanical
Properties of Novel gamma/gamma' Co-V-Ti-Based Superalloys
SO METALS
AB Microstructures, elemental partition behavior, phase stabilities and mechanical properties of Nb- and W-containing Co-V-Ti-based superalloys were investigated. Elemental partition coefficients (K-X = C-gamma/C gamma) of Nb and W in Co-V-Ti-based superalloys are 2.07 and 1.10, respectively. The gamma' solvus temperatures are determined as 1023 degrees C, 1055 degrees C and 1035 degrees C in Co-12V-4Ti, Co-10V-4Ti-2Nb and Co-10V-4Ti-2W alloys, which are higher than those of Co-9Al-9W alloy (1000 degrees C). The mass densities of quaternary Co-10V-4Ti-2Nb and Co-10V-4Ti-2W alloys are about 8.31 and 8.50 g.cm(-3), respectively, which are 15% lower than Co-Al-W-based superalloys (9.8 g.cm(-3)). All examined alloys exhibit an anomalous positive dependence on temperature rising from 600 to 750 degrees C. Strengths of all examined alloys are higher than those of MarM509 (traditional Cobalt-based superalloy) and Co-9Al-9W at all temperatures that we investigated. The maximum flow stress of Co-V-Ti-Nb alloy is about 638 MPa at 750 degrees C while that of Co-V-Ti-W alloy is about 588 MPa at 700 degrees C.
RI Han, Jiajia/I-3678-2019
OI Han, Jiajia/0000-0002-2642-0252
SN 2075-4701
PD JUL
PY 2018
VL 8
IS 7
AR 563
DI 10.3390/met8070563
UT WOS:000445096800093
ER
PT J
AU Yeh, AC
Wang, SC
Cheng, CF
Chang, YJ
Chang, SC
AF Yeh, An-Chou
Wang, Sheng-Chi
Cheng, Chia-Fu
Chang, Yao-Jen
Chang, Shih-Chin
TI Oxidation Behaviour of Si-Bearing Co-Based Alloys
SO OXIDATION OF METALS
AB The high-temperature oxidation behaviour of Si-bearing cobalt-base superalloys has been investigated. Isothermal oxidation tests conducted at 900, 1000, and 1150 A degrees C indicated that silicon addition can improve oxidation resistance. Furthermore, the alloy content of tungsten can have profound impact on the oxidation behaviour; low content of tungsten can promote the formation of protective alumina at temperatures at and above 1000 A degrees C, while high tungsten content can slow down oxidation at 900 A degrees C.
SN 0030-770X
EI 1573-4889
PD AUG
PY 2016
VL 86
IS 1-2
BP 99
EP 112
DI 10.1007/s11085-016-9623-2
UT WOS:000379175000006
ER
PT J
AU Suzuki, T
Yokokawa, T
Kobayashi, T
Koizumi, Y
Harada, H
Imai, H
AF Suzuki, Takanobu
Yokokawa, Tadaharu
Kobayashi, Toshiharu
Koizumi, Yutaka
Harada, Hiroshi
Imai, Hachiro
TI Effect of cobalt on microstructural parameters and mechanical properties
of Ni-base single crystal superalloys
SO JOURNAL OF THE JAPAN INSTITUTE OF METALS
AB The alloying effect of Cobalt (Co) to microstructural parameters and mechanical properties, such as partitioning ratios of alloying elements and creep strength, of Re-bearing Ni-base single crystal superalloys have been investigated. The second generation single crystal superalloys, TMS-82 +, Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3AI-6.0Ta-2.4Re-0.1Hf, in mass% (8Co) was compared to a Co-free (0Co) and 15 mass% Co (15Co) alloy which had the same chemical composition as TMS-82 + except that Co was changed.
It was shown that the partitioning ratios of alloying elements tend to k(= X-y/K-y') = 1, as the content of Co was increased.
Furthermore, it was found that there was suitable content of Co for the creep strength under various temperature-stress conditions.
SN 0021-4876
EI 1880-6880
PD FEB
PY 2007
VL 71
IS 2
BP 233
EP 238
DI 10.2320/jinstmet.71.233
UT WOS:000245020200018
ER
PT S
AU Liu, R
Yao, MX
AF Liu, Rong
Yao, Matthew X.
BE Zhang, S
Zhao, D
TI High-Performance Wear/Corrosion-Resistant Superalloys
SO AEROSPACE MATERIALS HANDBOOK
SE Advances in Materials Science and Engineering-Boca Raton
SN 2334-3656
BN 978-1-4398-7330-4; 978-1-4398-7329-8
PY 2013
BP 151
EP 235
UT WOS:000374501800006
ER
PT J
AU Zenk, CH
Neumeier, S
Engl, NM
Fries, SG
Dolotko, O
Weiser, M
Virtanen, S
Goken, M
AF Zenk, Christopher H.
Neumeier, Steffen
Engl, Nicole M.
Fries, Suzana G.
Dolotko, Oleksandr
Weiser, Martin
Virtanen, Sannakaisa
Goeken, Mathias
TI Intermediate Co/Ni-base model superalloys - Thermophysical properties,
creep and oxidation
SO SCRIPTA MATERIALIA
AB The mechanical properties of gamma'-strengthened Co-Ni-Al-W-Cr model superalloys extending from pure Ni-base to pure Co-base superalloys have been assessed. Differential scanning calorimetry measurements and thermodynamic calculations match well and show that the gamma' solvus temperature decreases with increasing Co-content The gamma/gamma' lattice misfit is negative on the Ni- and positive on the Co-rich side. High Ni-contents decelerate the oxidation kinetics up to a factor of 15. The creep strength of the Ni-base alloy increases by an order of magnitude with additions of Co before it deteriorates strongly upon higher additions despite an increasing gamma' volume fraction. (C) 2015 Elsevier Ltd. All rights reserved.
RI Neumeier, Steffen/F-7092-2017; Goken, Mathias/F-7940-2015; Virtanen,
Sannakaisa/N-3699-2015
OI Neumeier, Steffen/0000-0001-7853-0368; Goken,
Mathias/0000-0002-3226-0304; Zenk, Christopher/0000-0002-0690-4276;
Virtanen, Sannakaisa/0000-0002-7179-7593; Dolotko,
Oleksandr/0000-0002-6386-0281; Weiser, Martin/0000-0002-9448-5787
SN 1359-6462
PD FEB
PY 2016
VL 112
BP 83
EP 86
DI 10.1016/j.scriptamat.2015.09.018
UT WOS:000365057500019
ER
PT J
AU Wang, YQ
Sayre, G
AF Wang, Y. Q.
Sayre, G.
TI Synthesis of simple and platinum-modified aluminide coatings on cobalt
(Co)-base superalloys via a vapor phase aluminizing process
SO SURFACE & COATINGS TECHNOLOGY
AB An investigation was conducted to synthesize simple beta-CoAl or beta-(Co,Ni)Al coatings and platinum (Pt)-modified aluminide coatings on cobalt-base superalloys via an industrial vapor phase aluminizing process. Surface morphology and cross-section microstructure of the developed coatings were studied and compared by using optical microscope, scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Experimental results showed that Al increase in Al-Cr nuggets increases the coating thickness; substrate elements influence the formation of coatings; the increase of the electrodeposited Pt thickness increases the amount of xi PtAl(2) phase after aluminizing process; and the transformation of xi PtAl(2) phase into beta-(Co,Ni,Pt)Al phase can be obtained via a heat treatment process. (C) 2008 Elsevier B.V. All rights reserved.
SN 0257-8972
PD NOV 25
PY 2008
VL 203
IS 3-4
BP 256
EP 263
DI 10.1016/j.surfcoat.2008.08.072
UT WOS:000261360600011
ER
PT S
AU Suzuki, A
Inui, H
Pollock, TM
AF Suzuki, Akane
Inui, Haruyuki
Pollock, Tresa M.
BE Clarke, DR
TI L1(2)-Strengthened Cobalt-Base Superalloys
SO ANNUAL REVIEW OF MATERIALS RESEARCH, VOL 45
SE Annual Review of Materials Research
AB The discovery of the gamma'-Co-3(Al,W) phase with an L1(2) structure provided Co-base alloys with a new strengthening mechanism, enabling a new class of high-temperature material: Co-base superalloys. This review discusses the current understanding of the phase stability, deformation, and oxidation behaviors of gamma' single-phase and gamma + gamma' two-phase alloys in comparison with Ni-base gamma'-L1(2) phase and gamma + gamma' superalloys. Relatively low stacking fault energies and phase stability of the gamma' phase compared with those in Ni-base alloys are responsible for the unique deformation behaviors observed in Co-base gamma' and gamma + gamma' alloys. Controlling energies of planar defects, such as stacking faults and antiphase boundaries, by alloying is critical for alloy development. Experimental and density functional theory studies indicate that additions of Ta, Ti, Nb, Hf, and Ni are effective in simultaneously increasing the phase stability and stacking fault energy of gamma'-Co-3(Al,W), thus improving the high-temperature strength of Co-base gamma' phase and gamma + gamma' two-phase superalloys.
SN 1531-7331
BN 978-0-8243-1745-4
PY 2015
VL 45
BP 345
EP 368
DI 10.1146/annurev-matsci-070214-021043
UT WOS:000379904600002
ER
PT B
AU Dvorak, J
Kral, P
Kvapilova, M
Hrbacek, K
Sklenicka, V
AF Dvorak, Jiri
Kral, Petr
Kvapilova, Marie
Hrbacek, Karel
Sklenicka, Vaclav
GP TANGER Ltd
TI HIGH - TEMPERATURE CREEP BEHAVIOUR OF CAST COBALT-BASE SUPERALLOYS
SO 27TH INTERNATIONAL CONFERENCE ON METALLURGY AND MATERIALS (METAL 2018)
CT 27th International Conference on Metallurgy and Materials (METAL)
CY MAY 23-25, 2018
CL Brno, CZECH REPUBLIC
SP Techn Univ Ostrava, Czech Soc New Mat & Technologies, Engn Acad Czech Republ, Czech Met Soc, Mat Res Soc Serbia, Soc Portuguesa Mat, Austrian Soc Met & Mat, Norsk Materialteknisk Selskap, Assoc Italiana Metallurgia, Soc Francaise Metallurgie Materiaux
AB Two cast and heat-treated NbC and TaC - strengthened cobalt superalloys have been developed for an investment casting of spinner discs for glass wool industry. In this work constant load creep tests in tension were carried out in argon atmosphere at three testing temperature 900, 950 and 1000 degrees C and at the initial applied stresses ranging from 40 to 200 MPa. All the tests were continued until the final fracture. The results of creep testing were combined with microstructural and fractographic examinations by means of light and scanning electron microscopy. A mutual comparison of creep characteristics of the investigated superalloys under comparable creep loading conditions showed that NbC-strengthened superalloy exhibited longer creep life than TaC-strengthened one. Further, it was found that carbide precipitation is the primary strengthening mechanism in both cobalt-base superalloys under investigation and the amount, morphology and type of carbides have the decisive effect on the creep properties including creep damage and fracture processes. By contrast, CoNb superalloy exhibited a more brittle character of creep fracture mode than CoTa superalloy due to a premature fracture. This study was initiated to investigate in more details operating creep deformation processes and the effect of the creep microstructure and damage evolution on both investigated superalloys. The different behaviour and properties of studied superalloys were explained based on the received results of this study.
RI Kral, Petr/F-9777-2014
OI Kral, Petr/0000-0003-3838-1278
BN 978-80-87294-84-0
PY 2018
BP 530
EP 535
UT WOS:000461832200080
ER
PT J
AU Michon, S
Berthod, P
Aranda, L
Rapin, C
Podor, R
Steinmetz, P
AF Michon, S
Berthod, P
Aranda, L
Rapin, C
Podor, R
Steinmetz, P
TI Application of thermodynamic calculations to study high temperature
behavior of TaC-strengthened Co-base superalloys
SO CALPHAD-COMPUTER COUPLING OF PHASE DIAGRAMS AND THERMOCHEMISTRY
AB A database for cobalt-base superalloys was built up by combing the binary and ternary thermodynamic descriptions available in the SSOL (SGTE) database and from the literature. Using this database, results of thermodynamic calculations for several cobalt-base superalloys were compared to the experimentally observed n-microstructure of the alloys after homogenization at high temperatures and quenching. Three examples are presented: prediction of phase equilibria versus temperature and composition; selection of highly refractory materials using isothermal sections; and evaluation of local melting temperature in the case of skin formation of Co-base alloy during air oxidation at 1300 degreesC. The agreement between calculated prediction and experimental observation is satisfactory. (C) 2004 Elsevier Ltd. All rights reserved.
RI Podor, Renaud/N-3746-2019
OI Podor, Renaud/0000-0002-8103-1743; BERTHOD, Patrice/0000-0002-8035-927X
SN 0364-5916
EI 1873-2984
PD SEP
PY 2003
VL 27
IS 3
BP 289
EP 294
DI 10.1016/j.calphad.2003.12.003
UT WOS:000220038100006
ER
PT J
AU Suzuki, T
Yokokawa, T
Kobayashi, T
Harada, H
Imai, H
AF Suzuki, T
Yokokawa, T
Kobayashi, T
Harada, H
Imai, H
TI Effect of cobalt on micro-structural parameters of Ni-base single
crystal superalloys
SO JOURNAL OF THE JAPAN INSTITUTE OF METALS
AB Effect of Cobalt on micro-structural parameters, such as the lattice misfit and partitioning behaviors of alloying elements, of Re-bearing Ni-base single crystal superalloys have been investigated. The second-generation single crystal superalloys, TMS-82 + (Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass%), was compared to a Co-free (0Co) alloy which had the same chemical composition as TMS-82+ except that Co was removed.
The lattice misfit of 0Co alloy was found to be more negative value than that of TMS-82 + at any temperature. Additionally, when 0Co alloy was equilibrated at 1100 degrees C, Cr, Mo and W partitioned more into the gamma matrix; in contrast, Al and Ti partitioned into the gamma' precipitates. Increase in partitioning of Cr, Mo and W to the gamma phase resulted in an increase in the lattice parameter of gamma phase. Thus, lattice misfit of 0Co tend to more negative value than that of TMS-82 +.
SN 0021-4876
EI 1880-6880
PD FEB
PY 2006
VL 70
IS 2
BP 173
EP 175
DI 10.2320/jinstmet.70.173
UT WOS:000236785900018
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 Klein, L
Virtanen, S
AF Klein, L.
Virtanen, S.
TI Corrosion properties of novel gamma '-strengthened Co-base superalloys
SO CORROSION SCIENCE
AB Electrochemical properties of gamma'-strengthened Co-base superalloys with the composition Co-Al-W-B and Co-Al-W-B-Y are studied in comparison with pure Co at ambient temperature in 0.5 M NaCl aqueous solution (pH 5.8). The different materials exhibit comparable corrosion resistance with a limited initial passivation followed by severe pitting corrosion at higher potentials. Oxide layers, formed under isothermal oxidation at 800 and 900 degrees C, provide exceptional protection against pitting corrosion. No breakdown events are observed, even for thin layers formed during short-term oxidation (1 h at 900 degrees C). Si as alloying element further improves the corrosion behaviour of the oxidised alloy in NaCl. (C) 2012 Elsevier Ltd. All rights reserved.
RI Virtanen, Sannakaisa/N-3699-2015
OI Virtanen, Sannakaisa/0000-0002-7179-7593
SN 0010-938X
PD JAN
PY 2013
VL 66
BP 233
EP 241
DI 10.1016/j.corsci.2012.09.025
UT WOS:000313383800028
ER
PT J
AU Bantounas, I
Gwalani, B
Alam, T
Banerjee, R
Dye, D
AF Bantounas, Ioannis
Gwalani, Bharat
Alam, Talukder
Banerjee, Rajarshi
Dye, David
TI Elemental partitioning, mechanical and oxidation behaviour of two
high-gamma ' W-free gamma/gamma ' polycrystalline Co/Ni superalloys
SO SCRIPTA MATERIALIA
AB Cr-containing W-free Co alloys that form L1(2) gamma' strengthening precipitates in an fcc gamma matrix are presented to examine the effect of Ta and Nb additions to increase the strength, solvus temperature and gamma prime fraction. The alloys are found to have relatively low density, good oxidation resistance (<0.5 mu m scale at 800 degrees C for 100 h) with coherent Al2O3 and Cr2O3 scales, and reasonable yield strengths, similar to 800 MPa. The phase partitioning, measured by atom probe tomography, was found to be similar to W-containing Co/Ni superalloys, with Mo partitioning to the matrix providing solid solution strengthening. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Dye, David/B-5603-2012
OI Dye, David/0000-0002-8756-3513
SN 1359-6462
PD APR 1
PY 2019
VL 163
BP 44
EP 50
DI 10.1016/j.scriptamat.2018.12.025
UT WOS:000458940000010
ER
PT J
AU Mughrabi, H
AF Mughrabi, Hael
TI The importance of sign and magnitude of gamma/gamma ' lattice misfit in
superalloys-with special reference to the new gamma '-hardened
cobalt-base superalloys
SO ACTA MATERIALIA
AB In this work, the remarkable high-temperature strength properties of monocrystalline gamma'-hardened Ni-base superalloys are reviewed with the goal of understanding better the important role played by the gamma/gamma' lattice misfit delta with respect to microstructural stability and high-temperature creep and fatigue resistance. In particular, attention is focussed on the phenomenon of microstructural degradation by directional coarsening in the form of gamma/gamma' rafting which also occurs in turbine blades in service. The role played by the lattice misfit (which is negative for all currently used Ni-base superalloys) is elucidated with respect to its sign, magnitude and temperature dependence. Based on a detailed discussion of high-temperature deformation involving gamma/gamma' rafting, it is argued that superalloys with a positive gamma/gamma' lattice misfit should exhibit better high-temperature strength properties than otherwise similar superalloys with a negative misfit. In this context, the new class of gamma'-hardened Co-base superalloys is of special interest. These alloys have promising high-temperature strength properties and possess a positive lattice mismatch. It is suggested that this positive mismatch is one of the beneficial factors that contribute to the promising properties of these alloys and that this aspect should be explored further. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
SN 1359-6454
EI 1873-2453
PD DEC
PY 2014
VL 81
BP 21
EP 29
DI 10.1016/j.actamat.2014.08.005
UT WOS:000345179800003
ER
PT J
AU Zenk, CH
Povstugar, I
Li, R
Rinaldi, F
Neumeier, S
Raabe, D
Goken, M
AF Zenk, Christopher H.
Povstugar, Ivan
Li, Rui
Rinaldi, Fernando
Neumeier, Steffen
Raabe, Dierk
Goeken, Mathias
TI A novel type of Co-Ti-Cr-base gamma/gamma ' superalloys with low mass
density
SO ACTA MATERIALIA
AB A gamma' strengthened Co-Ti-Cr superalloy is presented with a mass density similar to 14 % below that of typical Co-Al-W-based alloys. The lattice misfit is sufficiently low to form coherent cuboidal gamma' precipitates. Atom probe tomography shows that Cr partitions to the gamma phase, but increases the gamma' volume fraction compared to a binary Co-Ti alloy to more than 60 %. The solubility of Cr in the gamma' phase is significantly higher than expected from previously published values. The gamma' solvus temperature is above 1100 degrees C. The yield strength shows a distinct increase above 600 degrees C surpassing that of Co-9Al-8W (at.%) and conventional Co-base superalloys, even more so when it is normalized by the mass density. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Raabe, Dierk/A-6470-2009; Neumeier, Steffen/F-7092-2017
OI Raabe, Dierk/0000-0003-0194-6124; Zenk, Christopher/0000-0002-0690-4276;
Povstugar, Ivan/0000-0002-1409-6854; Neumeier,
Steffen/0000-0001-7853-0368
SN 1359-6454
EI 1873-2453
PD AUG 15
PY 2017
VL 135
BP 244
EP 251
DI 10.1016/j.actamat.2017.06.024
UT WOS:000407536800025
ER
PT J
AU Gao, B
Wang, L
Liu, Y
Song, X
Yang, SY
Chiba, A
AF Gao, B.
Wang, L.
Liu, Y.
Song, X.
Yang, S. Y.
Chiba, A.
TI High temperature oxidation behaviour of gamma '-strengthened Co-based
superalloys with different Ni addition
SO CORROSION SCIENCE
AB High temperature oxidation behaviours of gamma'-strengthened Co-based superalloys with various Ni additions were investigated at both 800 degrees C and 900 degrees C. The results show that the superalloys show excellent oxidation resistance due to the formation of compact spinel oxide scales. With the increasing of Ni addition, the concentration of Cr in scale/alloy interface will be increased but that of Co will be decreased. And the growth of Cr2O3 will be promoted, while CoO nucleation will be hindered. Therefore, increasing Ni addition helps the formation of protective spinel oxide scales and delays nodular oxidation, which favours to be better oxidation resistance.
SN 0010-938X
EI 1879-0496
PD AUG 15
PY 2019
VL 157
BP 109
EP 115
DI 10.1016/j.corsci.2019.05.036
UT WOS:000480374200012
ER
PT J
AU Jokisaari, AM
Naghavi, SS
Wolverton, C
Voorhees, PW
Heinonen, OG
AF Jokisaari, A. M.
Naghavi, S. S.
Wolverton, C.
Voorhees, P. W.
Heinonen, O. G.
TI Predicting the morphologies of gamma ' precipitates in cobalt-based
superalloys
SO ACTA MATERIALIA
AB Cobalt-based alloys with gamma/gamma ' microstructures have the potential to become the next generation of superalloys, but alloy compositions and processing steps must be optimized to improve coarsening, creep, and rafting behavior. While these behaviors are different than in nickel-based superalloys, alloy development can be accelerated by understanding the thermodynamic factors influencing microstructure evolution. In this work, we develop a phase field model informed by first-principles density functional theory and experimental data to predict the equilibrium shapes of Co-Al-W gamma ' precipitates. Three-dimensional simulations of single and multiple precipitates are performed to understand the effect of elastic and interfacial energy on coarsened and rafted microstructures; the elastic energy is dependent on the elastic stiffnesses, misfit strain, precipitate size, applied stress, and precipitate spatial distribution. We observe characteristic microstructures dependent on the type of applied stress that have the same gamma ' morphology and orientation seen in experiments, indicating that the elastic stresses arising from coherent gamma/gamma ' interfaces are important for morphological evolution-during creep. The results also indicate that the narrow gamma channels between gamma ' precipitates are energetically favored, and provide an explanation for the experimentally observed directional coarsening that occurs without any applied stress. (c) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI Wolverton, Christopher/B-7542-2009; Voorhees, Peter/B-6700-2009
SN 1359-6454
EI 1873-2453
PD DEC
PY 2017
VL 141
BP 273
EP 284
DI 10.1016/j.actamat.2017.09.003
UT WOS:000415768100027
ER
PT J
AU Osada, T
Nagashima, N
Gu, YF
Yuan, Y
Yokokawa, T
Harada, H
AF Osada, Toshio
Nagashima, Nobuo
Gu, Yuefeng
Yuan, Yong
Yokokawa, Tadaharu
Harada, Hiroshi
TI Factors contributing to the strength of a polycrystalline nickel-cobalt
base superalloy
SO SCRIPTA MATERIALIA
AB The strengthening behaviors of a new polycrystalline Ni-Co base superalloy are analyzed by measuring its Vickers hardness over a range of structural scales, from nano to micro. The results clearly show, for the first time, the contributions of boundaries (grain, annealing twin and primary gamma') and secondary and tertiary gamma' precipitates in solid solutions to the total strength of such polycrystalline superalloys. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
RI OSADA, Toshio/D-3226-2014
OI Osada, Toshio/0000-0003-1539-9264
SN 1359-6462
PD MAY
PY 2011
VL 64
IS 9
BP 892
EP 895
DI 10.1016/j.scriptamat.2011.01.027
UT WOS:000288738400024
ER
PT J
AU Klein, L
Shen, Y
Killian, MS
Virtanen, S
AF Klein, L.
Shen, Y.
Killian, M. S.
Virtanen, S.
TI Effect of B and Cr on the high temperature oxidation behaviour of novel
gamma/gamma '-strengthened Co-base superalloys
SO CORROSION SCIENCE
AB Isothermal oxidation was carried out on new gamma/gamma'-strengthened Co-base superalloys of the system Co-Al-W-B and Co-Al-W-B-Cr at 800 and 900 degrees C in air. ToF-SIMS investigations show that boron accumulates in the inner oxide layer which improves the oxidation behaviour and oxide layer adhesion considerably. B-rich precipitations can be observed in the alloy matrix, as well. Appropriate amounts of chromium as additional alloying element lead to further improvement of the oxidation resistance due to the formation of protective inner Al(2)O(3) and Cr(2)O(3) scales. (C) 2011 Elsevier Ltd. All rights reserved.
RI Virtanen, Sannakaisa/N-3699-2015
OI Virtanen, Sannakaisa/0000-0002-7179-7593; Killian,
Manuela/0000-0003-0892-4614
SN 0010-938X
PD SEP
PY 2011
VL 53
IS 9
BP 2713
EP 2720
DI 10.1016/j.corsci.2011.04.020
UT WOS:000293157700005
ER
PT J
AU Casas, R
Galvez, F
Campos, M
AF Casas, R.
Galvez, F.
Campos, M.
TI Microstructural development of powder metallurgy cobalt-based
superalloys processed by field assisted sintering techniques (FAST)
SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES
MICROSTRUCTURE AND PROCESSING
AB This study reports the microstructural evolution, physical and mechanical properties of cobalt-based superalloys processed from mechanical alloyed powders and consolidated by field-assisted sintering techniques (FAST). After an initial thermodynamic simulation of the ternary diagram by Thermocalc (R) to determine the composition, a sequential milling process was carried out at room temperature up to 40 h milling of two different alloying systems: CO-12Al-10W (at%) and Co-12Al-10W-2Ti-2Ta (at%). Characterization of the powders was performed by using X-Ray diffraction, scanning electron microscope with energy-dispersive X-ray spectroscopy (EDS) and particle-size analyzer. Consolidated samples were also characterized in terms of density, microhardness and hardness. In order to promote the dual gamma/gamma' microstructure, both alloys were aged after solution annealing heat treatment, improving a new route of consolidation with a new level of performance.
RI Galvez Diaz-Rubio, Francisco/L-3201-2014; Campos, Monica/B-5213-2012
OI Galvez Diaz-Rubio, Francisco/0000-0002-3249-8865; Campos,
Monica/0000-0002-8360-9561
SN 0921-5093
EI 1873-4936
PD MAY 2
PY 2018
VL 724
BP 461
EP 468
DI 10.1016/j.msea.2018.04.004
UT WOS:000432640000050
ER
PT J
AU Kolb, M
Zenk, CH
Kirzinger, A
Povstugar, I
Raabe, D
Neumeier, S
Goken, M
AF Kolb, Markus
Zenk, Christopher H.
Kirzinger, Anna
Povstugar, Ivan
Raabe, Dierk
Neumeier, Steffen
Goeken, Mathias
TI Influence of rhenium on gamma '-strengthened cobalt-base superalloys
SO JOURNAL OF MATERIALS RESEARCH
AB The element Re is known to be a very potent strengthener concerning the creep properties of Ni-base superalloys. In this paper the influence of Re on the properties of new gamma'-strengthened Co-base superalloys is addressed. Atom probe tomography reveals that Re partitions preferentially to the gamma phase, but not as pronounced as in ni-base superalloys. Nanoindentation and micro-pillar compression tests of the gamma' phase indicate an increase of the hardness and the critical resolved shear stress caused by a considerable concentration of Re in the gamma' phase. Creep investigations show that the positive effect of Re is by far not as pronounced as in Ni-base superalloys. Several effects, which can contribute to this behavior, such as the lower Re concentration in gamma and hence a slightly reduced effective diffusion coefficient, a smaller diffusion barrier of Re in Cocompared to Ni, a slightly lower lattice misfit and gamma' volume fraction of the Re-containing alloy, are discussed.
RI Raabe, Dierk/A-6470-2009; Neumeier, Steffen/F-7092-2017
OI Raabe, Dierk/0000-0003-0194-6124; Zenk, Christopher/0000-0002-0690-4276;
Povstugar, Ivan/0000-0002-1409-6854; Neumeier,
Steffen/0000-0001-7853-0368
SN 0884-2914
EI 2044-5326
PD JUL
PY 2017
VL 32
IS 13
BP 2551
EP 2559
DI 10.1557/jmr.2017.242
UT WOS:000405627400012
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 Yu, H
Ukai, S
Hayashi, S
Ono, N
AF Yu, Hao
Ukai, Shigeharu
Hayashi, Shigenari
Ono, Naoko
TI Effect of Al content on the high-temperature oxidation of
Co-20Cr-(5,10)Al oxide dispersion strengthened superalloys
SO CORROSION SCIENCE
AB The high-temperature oxidation of Co-based oxide dispersion strengthened (ODS) Co-20Cr-(5, 10) Al-2.4Hf-1.5Y(2)O(3) (wt%) superalloys was investigated at 900 C-omicron and 1000 C-omicron. The 10Al (wt%) superalloys possess better oxidation resistance with the formation of alumina scale than the 5Al (wt%) with a duplex scale of CoCr2O4/Cr2O3 and internal Al2O3. The alumina on the 10Al superalloy is composed of theta- and alpha-alumina at 900 C-omicron but dominated by alpha-alumina at 1000 C-omicron. The lower weight gain of 10Al superalloys at 1000 C-omicron than at 900 C-omicron was associated with different growth mechanisms of the Al2O3 scales. (C) 2017 Elsevier Ltd. All rights reserved.
RI YU, Hao/H-7228-2018
SN 0010-938X
EI 1879-0496
PD APR
PY 2017
VL 118
BP 49
EP 59
DI 10.1016/j.corsci.2017.01.015
UT WOS:000396969800005
ER
PT S
AU Mukherji, D
Rosler, J
AF Mukherji, Debashis
Roesler, Joachim
BE Heilmaier, M
TI Design considerations and strengthening mechanisms in developing
Co-Re-based alloys for applications at+100 degrees C above
Ni-superalloys
SO EURO SUPERALLOYS 2010
SE Advanced Materials Research
CT European Symposium on Superalloys and their Applications
CY MAY 25-28, 2010
CL Wildbad Kreuth, GERMANY
AB Although Ni-base superalloys meet the gas turbine needs of today, they are used very close to their melting range. Demands for applications at higher temperatures are presently met partly through component cooling and application of thermal barrier coatings. However, this approach can not be sustained indefinitely unless the base metal melting temperature is also significantly increased. Rhenium addition can substantially increase the melting point in Co-base alloys and thereby provide a unique opportunity in the development of new alloys for very high temperatures - e.g. for applications at +100 degrees C metal temperature above present day single crystal Ni-base superalloys. The design considerations behind the Co-Re alloy development are presented in this paper. Selected results from the alloy development studies are also presented.