Effect of Al, Ti and Cr additions on the γ-γ’ microstructure of W-free Co-Ta-V-Based superalloys

Fernando L. Reyes Tirado; Spencer Taylor; David C. Dunand

doi:10.1016/j.actamat.2019.04.031

Effect of Al, Ti and Cr additions on the γ-γ’ microstructure of W-free Co-Ta-V-Based superalloys

Fernando L. Reyes Tirado, Spencer Taylor, David C. Dunand^*

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

57 Scopus citations

Abstract

The recently-discovered metastable γ′-Co₃(Ta_0.76V_0.24) 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 γ+γ′ microstructure, the γ′-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 γ/γ′ superalloy, Co-10Ni-5Al-3Ta-3V-2Ti-0.04B (at.%), with γ′ precipitates which are stable up to six weeks of aging at 850 °C, while slowly coarsening and coalescing from cuboidal to elongated shapes. After one day of aging at 850 °C, the γ′ nanoprecipitates have a (Co_0.83Ni_0.17)₃(Ta_0.42Al_0.23Ti_0.19V_0.15B_0.01) composition, with Al and Ti replacing at the same rate both Ta and V in the original metastable Co₃(Ta_0.76V_0.24) phase. To improve oxidation resistance, 4% Cr is added to the new superalloy, resulting in a somewhat higher volume fraction of finer cuboidal γ′ precipitates after one week of aging at 850 °C, but no other deleterious phases. These W- and Mo-free γ/γ′ superalloys show good creep resistance at 850 °C, on par with two other recent Co-base γ/γ′ 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.

Original language	English (US)
Pages (from-to)	44-54
Number of pages	11
Journal	Acta Materialia
Volume	172
DOIs	https://doi.org/10.1016/j.actamat.2019.04.031
State	Published - Jun 15 2019

Funding

This study was supported by the U.S. Department of Commerce , National Institute of Standards and Technology , as part of the Center for Hierarchical Materials Design (CHiMaD) at Northwestern University via award 70NANB14H012 . F.R.T acknowledges the support of a NSF Graduate Research Fellowship . S.T. acknowledges the support of the NU-MRSEC Research Experience for Undergraduates ( NSF DMR-1720139 ) and the 3M Corporation . This work made use of the MatCI Facility which receives support from the MRSEC Program ( NSF DMR- 1720139 ) of the Materials Research Center at Northwestern University ; the EPIC facility of Northwestern University’s NU ANCE Center , which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource ( NSF ECCS-1542205 ); the MRSEC program ( NSF DMR-1720139 ) at the Materials Research Center ; the International Institute for Nanotechnology (IIN) ; the Keck Foundation ; the State of Illinois , through the IIN . The authors gratefully acknowledge experimental assistance from Mr. Ding-Wen Chung, Ms. Francesca Long, Mr. Richard Michi and Dr. Amir Fakoosh (NU) and useful discussions with Mr. Ding-Wen Chung and Prof. D.N. Seidman (NU).

Keywords

Atom probe tomography (APT)
Cobalt-base superalloys
Creep
Microstructure
Precipitates

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Ceramics and Composites
Polymers and Plastics
Metals and Alloys

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10.1016/j.actamat.2019.04.031

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@article{c66944e1572b49a4aa6a6fca0f417135,

title = "Effect of Al, Ti and Cr additions on the γ-γ{\textquoteright} microstructure of W-free Co-Ta-V-Based superalloys",

abstract = "The recently-discovered metastable γ′-Co3(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 γ+γ′ microstructure, the γ′-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 γ/γ′ superalloy, Co-10Ni-5Al-3Ta-3V-2Ti-0.04B (at.%), with γ′ precipitates which are stable up to six weeks of aging at 850 °C, while slowly coarsening and coalescing from cuboidal to elongated shapes. After one day of aging at 850 °C, the γ′ 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 Co3(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 γ′ precipitates after one week of aging at 850 °C, but no other deleterious phases. These W- and Mo-free γ/γ′ superalloys show good creep resistance at 850 °C, on par with two other recent Co-base γ/γ′ 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.",

keywords = "Atom probe tomography (APT), Cobalt-base superalloys, Creep, Microstructure, Precipitates",

author = "{Reyes Tirado}, {Fernando L.} and Spencer Taylor and Dunand, {David C.}",

note = "Publisher Copyright: {\textcopyright} 2019 Acta Materialia Inc.",

year = "2019",

month = jun,

day = "15",

doi = "10.1016/j.actamat.2019.04.031",

language = "English (US)",

volume = "172",

pages = "44--54",

journal = "Acta Materialia",

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TY - JOUR

T1 - Effect of Al, Ti and Cr additions on the γ-γ’ microstructure of W-free Co-Ta-V-Based superalloys

AU - Reyes Tirado, Fernando L.

AU - Taylor, Spencer

AU - Dunand, David C.

PY - 2019/6/15

Y1 - 2019/6/15

N2 - The recently-discovered metastable γ′-Co3(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 γ+γ′ microstructure, the γ′-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 γ/γ′ superalloy, Co-10Ni-5Al-3Ta-3V-2Ti-0.04B (at.%), with γ′ precipitates which are stable up to six weeks of aging at 850 °C, while slowly coarsening and coalescing from cuboidal to elongated shapes. After one day of aging at 850 °C, the γ′ 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 Co3(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 γ′ precipitates after one week of aging at 850 °C, but no other deleterious phases. These W- and Mo-free γ/γ′ superalloys show good creep resistance at 850 °C, on par with two other recent Co-base γ/γ′ 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.

AB - The recently-discovered metastable γ′-Co3(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 γ+γ′ microstructure, the γ′-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 γ/γ′ superalloy, Co-10Ni-5Al-3Ta-3V-2Ti-0.04B (at.%), with γ′ precipitates which are stable up to six weeks of aging at 850 °C, while slowly coarsening and coalescing from cuboidal to elongated shapes. After one day of aging at 850 °C, the γ′ 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 Co3(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 γ′ precipitates after one week of aging at 850 °C, but no other deleterious phases. These W- and Mo-free γ/γ′ superalloys show good creep resistance at 850 °C, on par with two other recent Co-base γ/γ′ 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.

KW - Atom probe tomography (APT)

KW - Cobalt-base superalloys

KW - Creep

KW - Microstructure

KW - Precipitates

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DO - 10.1016/j.actamat.2019.04.031

M3 - Article

AN - SCOPUS:85064918053

SN - 1359-6454

VL - 172

SP - 44

EP - 54

JO - Acta Materialia

JF - Acta Materialia

ER -

Effect of Al, Ti and Cr additions on the γ-γ’ microstructure of W-free Co-Ta-V-Based superalloys

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Keywords

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