Small punch creep testing of thermally sprayed Stellite 6 coating: A comparative study of as-received vs post-heat treatment

G.A. Jackson; M. Bai; Z. Pala; T. Hussain; W. Sun

doi:10.1016/j.msea.2019.02.030

Small punch creep testing of thermally sprayed Stellite 6 coating: A comparative study of as-received vs post-heat treatment

G.A. Jackson, M. Bai, Z. Pala, T. Hussain, W. Sun

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

2 Citations (Scopus)

15 Downloads (Pure)

Abstract

Thermally sprayed Stellite 6 coatings offer high wear and corrosion-erosion resistance at high temperature but the creep behaviour of such coatings is not well understood. In this paper, the microstructure and creep behaviour of a HVOF Stellite 6 coating was investigated. The coating was tested in the as-sprayed condition and after an isothermal heat-treatment of 1 h at 1050 °C. The as-sprayed coating comprised FCC Co-Cr-W solid solution with 2–3 wt% HCP phase, whereas the heat-treated coating comprised FCC Co-Cr-W solid solution, 11 wt% M23C6 carbides and 7 wt% M7C3 carbides. Small punch creep tests were conducted at 700 °C on the as-sprayed and heat-treated coatings. The heat-treated coating exhibited minimum steady-state strain rates approximately 2 orders of magnitude lower than the as-sprayed coating when tested at similar loads, leading to times to failure approximately two orders of magnitude longer for the heat-treated coating within the selected load range. Fracture analysis showed cracking along powder particle boundaries was the main mode of cracking in the as-sprayed coating whereas for the heat-treated coating, fracture along the carbide / matrix interface was the main fracture mechanism.

Original language	English
Pages (from-to)	137-147
Number of pages	11
Journal	Materials Science and Engineering: A
Volume	749
Early online date	10 Feb 2019
DOIs	https://doi.org/10.1016/j.msea.2019.02.030
Publication status	Published - 11 Mar 2019
Externally published	Yes

Bibliographical note

© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/BY/4.0/).

Keywords

Small punch creep
HVOF
Stellite 6
Fracture
Mechanical properties

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title = "Small punch creep testing of thermally sprayed Stellite 6 coating: A comparative study of as-received vs post-heat treatment",

abstract = "Thermally sprayed Stellite 6 coatings offer high wear and corrosion-erosion resistance at high temperature but the creep behaviour of such coatings is not well understood. In this paper, the microstructure and creep behaviour of a HVOF Stellite 6 coating was investigated. The coating was tested in the as-sprayed condition and after an isothermal heat-treatment of 1 h at 1050 °C. The as-sprayed coating comprised FCC Co-Cr-W solid solution with 2–3 wt% HCP phase, whereas the heat-treated coating comprised FCC Co-Cr-W solid solution, 11 wt% M23C6 carbides and 7 wt% M7C3 carbides. Small punch creep tests were conducted at 700 °C on the as-sprayed and heat-treated coatings. The heat-treated coating exhibited minimum steady-state strain rates approximately 2 orders of magnitude lower than the as-sprayed coating when tested at similar loads, leading to times to failure approximately two orders of magnitude longer for the heat-treated coating within the selected load range. Fracture analysis showed cracking along powder particle boundaries was the main mode of cracking in the as-sprayed coating whereas for the heat-treated coating, fracture along the carbide / matrix interface was the main fracture mechanism.",

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AU - Hussain, T.

AU - Sun, W.

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N2 - Thermally sprayed Stellite 6 coatings offer high wear and corrosion-erosion resistance at high temperature but the creep behaviour of such coatings is not well understood. In this paper, the microstructure and creep behaviour of a HVOF Stellite 6 coating was investigated. The coating was tested in the as-sprayed condition and after an isothermal heat-treatment of 1 h at 1050 °C. The as-sprayed coating comprised FCC Co-Cr-W solid solution with 2–3 wt% HCP phase, whereas the heat-treated coating comprised FCC Co-Cr-W solid solution, 11 wt% M23C6 carbides and 7 wt% M7C3 carbides. Small punch creep tests were conducted at 700 °C on the as-sprayed and heat-treated coatings. The heat-treated coating exhibited minimum steady-state strain rates approximately 2 orders of magnitude lower than the as-sprayed coating when tested at similar loads, leading to times to failure approximately two orders of magnitude longer for the heat-treated coating within the selected load range. Fracture analysis showed cracking along powder particle boundaries was the main mode of cracking in the as-sprayed coating whereas for the heat-treated coating, fracture along the carbide / matrix interface was the main fracture mechanism.

AB - Thermally sprayed Stellite 6 coatings offer high wear and corrosion-erosion resistance at high temperature but the creep behaviour of such coatings is not well understood. In this paper, the microstructure and creep behaviour of a HVOF Stellite 6 coating was investigated. The coating was tested in the as-sprayed condition and after an isothermal heat-treatment of 1 h at 1050 °C. The as-sprayed coating comprised FCC Co-Cr-W solid solution with 2–3 wt% HCP phase, whereas the heat-treated coating comprised FCC Co-Cr-W solid solution, 11 wt% M23C6 carbides and 7 wt% M7C3 carbides. Small punch creep tests were conducted at 700 °C on the as-sprayed and heat-treated coatings. The heat-treated coating exhibited minimum steady-state strain rates approximately 2 orders of magnitude lower than the as-sprayed coating when tested at similar loads, leading to times to failure approximately two orders of magnitude longer for the heat-treated coating within the selected load range. Fracture analysis showed cracking along powder particle boundaries was the main mode of cracking in the as-sprayed coating whereas for the heat-treated coating, fracture along the carbide / matrix interface was the main fracture mechanism.

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