Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at%) superalloys

Peter J. Bocchini*, Chantal K. Sudbrack, Ronald D. Noebe, David C Dunand, David N Seidman

*Corresponding author for this work

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Polycrystalline Co-10Ni-(9 – x)Al-(9 – x)W-2xTi at% (x = 0, 1, 2, 3, 4) alloys with γ(f.c.c.) plus γ′(L12) microstructures are investigated, where the γ′(L12)-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal γ′(L12)-precipitates grow and develop a rounded morphology. After 256 h of aging at 1000 °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, ϕ, of the γ′(L12)-phase from <R> = 463 nm and ϕ = 8% for 2 at% Ti to <R> = 722 nm and ϕ = 52% for 8 at% Ti. Composition measurements of the γ(f.c.c.)-matrix and γ′(L12)-precipitates demonstrate that Ti substitutes for W and Al in the γ′(L12)-precipitates, increases the partitioning of W to γ′(L12), and changes the partitioning behavior of Al from a mild γ′(L12)-former to a mild γ(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely μ(Co7W6)-type, which do not destabilize the γ(f.c.c.) plus γ′(L12) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys’ mass density decrease; (ii) the γ′(L12)-solvus temperature increases; (iii) the γ′(L12) volume fraction formed during aging at 1273 K (1000 °C) increases; and (iv) the 0.2% offset flow stress increases.

Original languageEnglish (US)
Pages (from-to)122-132
Number of pages11
JournalMaterials Science and Engineering A
Volume705
DOIs
StatePublished - Sep 29 2017

Fingerprint

Tungsten
heat resistant alloys
Titanium
Aluminum
Superalloys
Precipitates
precipitates
tungsten
Substitution reactions
titanium
substitutes
aluminum
Aging of materials
Volume fraction
microstructure
Microstructure
Plastic flow
Grain boundaries
grain boundaries
radii

Keywords

  • Cobalt superalloy
  • Flow stress
  • Gamma prime
  • High-temperature stability
  • Precipitation strengthening

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

@article{101999997ee649d888df2fc790cd01e7,
title = "Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at{\%}) superalloys",
abstract = "Polycrystalline Co-10Ni-(9 – x)Al-(9 – x)W-2xTi at{\%} (x = 0, 1, 2, 3, 4) alloys with γ(f.c.c.) plus γ′(L12) microstructures are investigated, where the γ′(L12)-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal γ′(L12)-precipitates grow and develop a rounded morphology. After 256 h of aging at 1000 °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, ϕ, of the γ′(L12)-phase from <R> = 463 nm and ϕ = 8{\%} for 2 at{\%} Ti to <R> = 722 nm and ϕ = 52{\%} for 8 at{\%} Ti. Composition measurements of the γ(f.c.c.)-matrix and γ′(L12)-precipitates demonstrate that Ti substitutes for W and Al in the γ′(L12)-precipitates, increases the partitioning of W to γ′(L12), and changes the partitioning behavior of Al from a mild γ′(L12)-former to a mild γ(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely μ(Co7W6)-type, which do not destabilize the γ(f.c.c.) plus γ′(L12) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys’ mass density decrease; (ii) the γ′(L12)-solvus temperature increases; (iii) the γ′(L12) volume fraction formed during aging at 1273 K (1000 °C) increases; and (iv) the 0.2{\%} offset flow stress increases.",
keywords = "Cobalt superalloy, Flow stress, Gamma prime, High-temperature stability, Precipitation strengthening",
author = "Bocchini, {Peter J.} and Sudbrack, {Chantal K.} and Noebe, {Ronald D.} and Dunand, {David C} and Seidman, {David N}",
year = "2017",
month = "9",
day = "29",
doi = "10.1016/j.msea.2017.08.034",
language = "English (US)",
volume = "705",
pages = "122--132",
journal = "Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing",
issn = "0921-5093",
publisher = "Elsevier BV",

}

Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at%) superalloys. / Bocchini, Peter J.; Sudbrack, Chantal K.; Noebe, Ronald D.; Dunand, David C; Seidman, David N.

In: Materials Science and Engineering A, Vol. 705, 29.09.2017, p. 122-132.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at%) superalloys

AU - Bocchini, Peter J.

AU - Sudbrack, Chantal K.

AU - Noebe, Ronald D.

AU - Dunand, David C

AU - Seidman, David N

PY - 2017/9/29

Y1 - 2017/9/29

N2 - Polycrystalline Co-10Ni-(9 – x)Al-(9 – x)W-2xTi at% (x = 0, 1, 2, 3, 4) alloys with γ(f.c.c.) plus γ′(L12) microstructures are investigated, where the γ′(L12)-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal γ′(L12)-precipitates grow and develop a rounded morphology. After 256 h of aging at 1000 °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, ϕ, of the γ′(L12)-phase from <R> = 463 nm and ϕ = 8% for 2 at% Ti to <R> = 722 nm and ϕ = 52% for 8 at% Ti. Composition measurements of the γ(f.c.c.)-matrix and γ′(L12)-precipitates demonstrate that Ti substitutes for W and Al in the γ′(L12)-precipitates, increases the partitioning of W to γ′(L12), and changes the partitioning behavior of Al from a mild γ′(L12)-former to a mild γ(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely μ(Co7W6)-type, which do not destabilize the γ(f.c.c.) plus γ′(L12) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys’ mass density decrease; (ii) the γ′(L12)-solvus temperature increases; (iii) the γ′(L12) volume fraction formed during aging at 1273 K (1000 °C) increases; and (iv) the 0.2% offset flow stress increases.

AB - Polycrystalline Co-10Ni-(9 – x)Al-(9 – x)W-2xTi at% (x = 0, 1, 2, 3, 4) alloys with γ(f.c.c.) plus γ′(L12) microstructures are investigated, where the γ′(L12)-formers Al and W are replaced with Ti. Upon aging, the initially cuboidal γ′(L12)-precipitates grow and develop a rounded morphology. After 256 h of aging at 1000 °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, ϕ, of the γ′(L12)-phase from <R> = 463 nm and ϕ = 8% for 2 at% Ti to <R> = 722 nm and ϕ = 52% for 8 at% Ti. Composition measurements of the γ(f.c.c.)-matrix and γ′(L12)-precipitates demonstrate that Ti substitutes for W and Al in the γ′(L12)-precipitates, increases the partitioning of W to γ′(L12), and changes the partitioning behavior of Al from a mild γ′(L12)-former to a mild γ(f.c.c.)-former. The grain boundaries in the aged alloys exhibit W-rich precipitates, most likely μ(Co7W6)-type, which do not destabilize the γ(f.c.c.) plus γ′(L12) microstructure within the grains. Four important benefits accrue from replacing W and Al with Ti: (i) the alloys’ mass density decrease; (ii) the γ′(L12)-solvus temperature increases; (iii) the γ′(L12) volume fraction formed during aging at 1273 K (1000 °C) increases; and (iv) the 0.2% offset flow stress increases.

KW - Cobalt superalloy

KW - Flow stress

KW - Gamma prime

KW - High-temperature stability

KW - Precipitation strengthening

UR - http://www.scopus.com/inward/record.url?scp=85027960475&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85027960475&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2017.08.034

DO - 10.1016/j.msea.2017.08.034

M3 - Article

VL - 705

SP - 122

EP - 132

JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

SN - 0921-5093

ER -