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Cavitation erosion performance of CVD W/WC coatings

Cavitation erosion performance of CVD W/WC coatings
Cavitation erosion performance of CVD W/WC coatings
In the aviation industry, water droplet erosion (WDE) takes place when an aircraft takes off on as wet runway or flies through rain or clouds. The leading edge of turbofan blades suffers from high-speed (300-400 m/s) impingements of water droplets, resulting in material removal that subsequently changes the leading edge profile and surface roughness. This affects the aerodynamic performance of turbofan blades, which eventually leads to efficiency drop of the aircraft engine and the need to replace and/or recondition the blades. A coating solution is targeted, such that, not only that it resists the high impact pressure but also inhibits stress wave reinforcements at the coating-substrate or interlayers interfaces. Past studies indicate similar damage mechanisms to WDE are generated by cavitation erosion (CE) during the early stages (incubation). Hence, CE is introduced in this study to predict the WDE performance. The coatings studied were nanostructured CVD tungsten/tungsten carbide coatings, either hierarchical or monotonic in design, on Ti6Al4V alloy grade 5 substrates. In-depth understanding on the coating damage mechanisms are established by correlating the coating performance with microstructure, crystallographic texture, interface design, coating deposition conditions and mechanical properties for the first time. A particular crystalline texture was found that gives optimum performance. The effect of the initial coating topography on the CE performance is effectively characterised by the surface parameters Ssk and Sku. The damage was found to initiate at the grain boundaries of the exposed surfaces. The hierarchical coating microstructure demonstrated enhancement in CE performance compared to a monotonic columnar grain structure. Additionally, it is found that the coating performance under dynamic compressive loadings could not be predicted by a simple H/E approaches. However, combining the H/E ratios with the factors of microstructure and crystal orientations might further facilitate the understanding of coating performances along with better understanding of the role of compressive residual stresses and stress waves propagation or reinforcement through coating depth and at the top surface of the coating.
cavitation, water droplet erosion (WDE), erosion resistance, CVD coating, nanostructured tungsten/tungsten carbide, hierarchical and monotonic coatings
0043-1648
Ma, Dina
ae2dcfae-cf5b-4492-b6dc-2e6b86960431
Harvey, Terence
3b94322b-18da-4de8-b1af-56d202677e04
Zhuk, Yuri N.
4bc28e9c-147f-4bdb-96e3-4547e7fcd371
Wellman, Richard
933354f5-e4ff-448e-b6b5-4caef14187a4
Wood, Robert
d9523d31-41a8-459a-8831-70e29ffe8a73
Ma, Dina
ae2dcfae-cf5b-4492-b6dc-2e6b86960431
Harvey, Terence
3b94322b-18da-4de8-b1af-56d202677e04
Zhuk, Yuri N.
4bc28e9c-147f-4bdb-96e3-4547e7fcd371
Wellman, Richard
933354f5-e4ff-448e-b6b5-4caef14187a4
Wood, Robert
d9523d31-41a8-459a-8831-70e29ffe8a73

Ma, Dina, Harvey, Terence, Zhuk, Yuri N., Wellman, Richard and Wood, Robert (2020) Cavitation erosion performance of CVD W/WC coatings. Wear, 452–453, [203276]. (doi:10.1016/j.wear.2020.203276).

Record type: Article

Abstract

In the aviation industry, water droplet erosion (WDE) takes place when an aircraft takes off on as wet runway or flies through rain or clouds. The leading edge of turbofan blades suffers from high-speed (300-400 m/s) impingements of water droplets, resulting in material removal that subsequently changes the leading edge profile and surface roughness. This affects the aerodynamic performance of turbofan blades, which eventually leads to efficiency drop of the aircraft engine and the need to replace and/or recondition the blades. A coating solution is targeted, such that, not only that it resists the high impact pressure but also inhibits stress wave reinforcements at the coating-substrate or interlayers interfaces. Past studies indicate similar damage mechanisms to WDE are generated by cavitation erosion (CE) during the early stages (incubation). Hence, CE is introduced in this study to predict the WDE performance. The coatings studied were nanostructured CVD tungsten/tungsten carbide coatings, either hierarchical or monotonic in design, on Ti6Al4V alloy grade 5 substrates. In-depth understanding on the coating damage mechanisms are established by correlating the coating performance with microstructure, crystallographic texture, interface design, coating deposition conditions and mechanical properties for the first time. A particular crystalline texture was found that gives optimum performance. The effect of the initial coating topography on the CE performance is effectively characterised by the surface parameters Ssk and Sku. The damage was found to initiate at the grain boundaries of the exposed surfaces. The hierarchical coating microstructure demonstrated enhancement in CE performance compared to a monotonic columnar grain structure. Additionally, it is found that the coating performance under dynamic compressive loadings could not be predicted by a simple H/E approaches. However, combining the H/E ratios with the factors of microstructure and crystal orientations might further facilitate the understanding of coating performances along with better understanding of the role of compressive residual stresses and stress waves propagation or reinforcement through coating depth and at the top surface of the coating.

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Manuscript_V6 (Wood R.J.) - Accepted Manuscript
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Accepted/In Press date: 20 March 2020
e-pub ahead of print date: 25 March 2020
Keywords: cavitation, water droplet erosion (WDE), erosion resistance, CVD coating, nanostructured tungsten/tungsten carbide, hierarchical and monotonic coatings

Identifiers

Local EPrints ID: 438943
URI: http://eprints.soton.ac.uk/id/eprint/438943
ISSN: 0043-1648
PURE UUID: 060472a6-4a82-4c49-988b-7208a799ad69
ORCID for Robert Wood: ORCID iD orcid.org/0000-0003-0681-9239

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Date deposited: 27 Mar 2020 17:30
Last modified: 17 Mar 2024 05:25

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Contributors

Author: Dina Ma
Author: Terence Harvey
Author: Yuri N. Zhuk
Author: Richard Wellman
Author: Robert Wood ORCID iD

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