Oxidation behavior of co-doped NiCrAl alloys in dry and wet air

Kinga A. Unocic; Bruce A. Pint

doi:10.1016/j.surfcoat.2013.07.068

Oxidation behavior of co-doped NiCrAl alloys in dry and wet air

Kinga A. Unocic, Bruce A. Pint

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

50 Scopus citations

Abstract

Cast NiCrAl alloys with additions of Y, La, Hf and Ti were evaluated at 1100°C in wet (10 and 50% H₂O) and dry air (0% H₂O) in order to optimize such dopants for superalloy bond coatings. The results suggest that the typical Y addition in most coatings could be replaced by La. Also, scale adhesion in cyclic testing was improved with the co-addition of Hf with La or Y. Ti was added to investigate its incorporation in coatings on superalloys containing significant Ti additions. Particularly with co-doped alloys, the addition of Ti had little effect on scale adhesion but did reduce the depth of internal oxidation. Water vapor increased spallation, especially for the least adherent alloys, such as Y,Ti-doped NiCrAl. For the co-doped compositions with Hf, water vapor had a limited effect on scale adhesion and on the alumina growth rate in isothermal exposures. In addition to specimen mass change, the extent of internal oxidation and the depletion of β phase in the substrate were evaluated. Analytical transmission electron microscopy showed that Y, La and Hf co-segregated to the alumina scale grain boundaries and formed dopant-rich oxide precipitates in the scale.

Original language	English
Pages (from-to)	8-15
Number of pages	8
Journal	Surface and Coatings Technology
Volume	237
DOIs	https://doi.org/10.1016/j.surfcoat.2013.07.068
State	Published - Dec 25 2013

Funding

The authors would like to thank G. W. Garner, T. M. Lowe, T. Geer, T. Jordan and D. W. Coffey for assistance with the experimental work. S. N. Dryepondt and L. F. Allard Jr. provided helpful comments and suggestions on the results and manuscript. Research was supported by the U.S. Department of Energy, Office of Coal and Power R&D, Office of Fossil Energy, and ORNL's Shared Research Equipment (ShaRE) User Facility, which is sponsored by the Office of Basic Energy Sciences, U.S. Department of Energy.

Funders	Funder number
Office of Basic Energy Sciences
Office of Coal and Power R&D
U.S. Department of Energy
Office of Fossil Energy
Oak Ridge National Laboratory

Keywords

Hf, Y, Ti and La segregation
NiCrAl
Reactive elements
Water vapor
α-AlO

Access to Document

10.1016/j.surfcoat.2013.07.068

Cite this

@article{58d283c7db444f88916866a93438c02a,

title = "Oxidation behavior of co-doped NiCrAl alloys in dry and wet air",

abstract = "Cast NiCrAl alloys with additions of Y, La, Hf and Ti were evaluated at 1100°C in wet (10 and 50% H2O) and dry air (0% H2O) in order to optimize such dopants for superalloy bond coatings. The results suggest that the typical Y addition in most coatings could be replaced by La. Also, scale adhesion in cyclic testing was improved with the co-addition of Hf with La or Y. Ti was added to investigate its incorporation in coatings on superalloys containing significant Ti additions. Particularly with co-doped alloys, the addition of Ti had little effect on scale adhesion but did reduce the depth of internal oxidation. Water vapor increased spallation, especially for the least adherent alloys, such as Y,Ti-doped NiCrAl. For the co-doped compositions with Hf, water vapor had a limited effect on scale adhesion and on the alumina growth rate in isothermal exposures. In addition to specimen mass change, the extent of internal oxidation and the depletion of β phase in the substrate were evaluated. Analytical transmission electron microscopy showed that Y, La and Hf co-segregated to the alumina scale grain boundaries and formed dopant-rich oxide precipitates in the scale.",

keywords = "Hf, Y, Ti and La segregation, NiCrAl, Reactive elements, Water vapor, α-AlO",

author = "Unocic, {Kinga A.} and Pint, {Bruce A.}",

year = "2013",

month = dec,

day = "25",

doi = "10.1016/j.surfcoat.2013.07.068",

language = "English",

volume = "237",

pages = "8--15",

journal = "Surface and Coatings Technology",

issn = "0257-8972",

publisher = "Elsevier",

}

TY - JOUR

T1 - Oxidation behavior of co-doped NiCrAl alloys in dry and wet air

AU - Unocic, Kinga A.

AU - Pint, Bruce A.

PY - 2013/12/25

Y1 - 2013/12/25

N2 - Cast NiCrAl alloys with additions of Y, La, Hf and Ti were evaluated at 1100°C in wet (10 and 50% H2O) and dry air (0% H2O) in order to optimize such dopants for superalloy bond coatings. The results suggest that the typical Y addition in most coatings could be replaced by La. Also, scale adhesion in cyclic testing was improved with the co-addition of Hf with La or Y. Ti was added to investigate its incorporation in coatings on superalloys containing significant Ti additions. Particularly with co-doped alloys, the addition of Ti had little effect on scale adhesion but did reduce the depth of internal oxidation. Water vapor increased spallation, especially for the least adherent alloys, such as Y,Ti-doped NiCrAl. For the co-doped compositions with Hf, water vapor had a limited effect on scale adhesion and on the alumina growth rate in isothermal exposures. In addition to specimen mass change, the extent of internal oxidation and the depletion of β phase in the substrate were evaluated. Analytical transmission electron microscopy showed that Y, La and Hf co-segregated to the alumina scale grain boundaries and formed dopant-rich oxide precipitates in the scale.

AB - Cast NiCrAl alloys with additions of Y, La, Hf and Ti were evaluated at 1100°C in wet (10 and 50% H2O) and dry air (0% H2O) in order to optimize such dopants for superalloy bond coatings. The results suggest that the typical Y addition in most coatings could be replaced by La. Also, scale adhesion in cyclic testing was improved with the co-addition of Hf with La or Y. Ti was added to investigate its incorporation in coatings on superalloys containing significant Ti additions. Particularly with co-doped alloys, the addition of Ti had little effect on scale adhesion but did reduce the depth of internal oxidation. Water vapor increased spallation, especially for the least adherent alloys, such as Y,Ti-doped NiCrAl. For the co-doped compositions with Hf, water vapor had a limited effect on scale adhesion and on the alumina growth rate in isothermal exposures. In addition to specimen mass change, the extent of internal oxidation and the depletion of β phase in the substrate were evaluated. Analytical transmission electron microscopy showed that Y, La and Hf co-segregated to the alumina scale grain boundaries and formed dopant-rich oxide precipitates in the scale.

KW - Hf, Y, Ti and La segregation

KW - NiCrAl

KW - Reactive elements

KW - Water vapor

KW - α-AlO

UR - http://www.scopus.com/inward/record.url?scp=84889089953&partnerID=8YFLogxK

U2 - 10.1016/j.surfcoat.2013.07.068

DO - 10.1016/j.surfcoat.2013.07.068

M3 - Article

AN - SCOPUS:84889089953

SN - 0257-8972

VL - 237

SP - 8

EP - 15

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

ER -

Oxidation behavior of co-doped NiCrAl alloys in dry and wet air

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this