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Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

Performance Metrics and Experimental Testing of Erosion-Resistant Compressor Blade Coatings

[+] Author and Article Information
Sean G. Leithead

Department of Mechanical
and Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada
e-mail: sean.leithead@rmc.ca

William D. E. Allan

Department of Mechanical
and Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON K7K 7B4, Canada
e-mail: billy.allan@rmc.ca

Linruo Zhao

Institute for Aerospace Research,
National Research Council of Canada,
Ottawa, ON K1A 0R6, Canada
e-mail: linruo.zhao@nrc-cnrc.gc.ca

1Corresponding author.

Contributed by the Manufacturing Materials and Metallurgy Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 31, 2014; final manuscript received September 23, 2014; published online December 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(5), 052101 (May 01, 2015) (11 pages) Paper No: GTP-14-1453; doi: 10.1115/1.4028719 History: Received July 31, 2014; Revised September 23, 2014; Online December 02, 2014

A durability test rig for erosion-resistant gas turbine engine compressor blade coatings was designed and commissioned. Bare and coated 17-4PH steel modified NACA 6505-profile blades were spun at an average speed of 10,860 rpm and exposed to garnet sand-laden air for 5 h at an average sand concentration of 2.5 g/(m3 of air) and a blade leading edge (LE) Mach number of 0.50. The rig was designed to represent a first stage axial compressor. Two 16 μm-thick coatings were tested: Titanium nitride (TiN) and chromium–aluminum–titanium nitride (CrAlTiN), both applied using an arc physical vapor deposition (PVD) technique. A composite scale, defined as the Leithead-Allan-Zhao (LAZ) score, was devised to compare the durability performance of bare and coated blades based on mass-loss and blade dimension changes. The bare blades' LAZ score was set as a benchmark of 1.00, with the TiN-coated and CrAlTiN-coated blades obtaining respective scores of 0.69 and 0.41. A lower score identified a more erosion-resistant coating. Major locations of blade wear included: trailing edge (TE), LE, and rear suction surface (SS). TE thickness was reduced, the LE became blunt, and the rear SS was scrubbed by overtip and recirculation zone vortices. The erosion effects of secondary flows were found to be significant. Erosion damage due to reflected particles was absent due to a low blade solidity of 0.7. The rig is best suited for durability evaluation of erosion-resistant coatings after (AF) being proven worthy of consideration for gas turbine engines through ASTM standardized testing.

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References

Figures

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Fig. 1

RMC erosion rig schematic

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Fig. 2

Airflow velocity at the blade LE (airflow from left as per convention)

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Fig. 3

Blade assembly AF silver-soldering and bead blasting: (a) side view and (b) front view

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Fig. 4

Rainbow blade test pattern: (a) rotor & blades in rotor housing, (b) blade coatings used, and (c) rotor assembly & blades

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Fig. 5

Blade LE & forward PS region photos BE & AF 5 h of erosion (airflow from left to right, scale: 1 mm per increment): bare 17-4PH steel (a) BE and (b) AF; TiN-coated (c) BE and (d) AF; CrAlTiN-coated (e) BE and (f) AF (adapted from Ref. [12])

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Fig. 6

Bare 17-4PH steel blade SS (airflow from left to right, scale: 1 mm per increment): (a) oil-flow visualization, (b) AF 1 h of erosion (annotated), and (c) AF 5 h of erosion (adapted from Ref. [12])

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Fig. 7

Proposed flow phenomena occurring at sections annotated in Fig. 6(b): (a) Section A-A, (b) Section B-B, and (c) Section C-C (adapted from Ref. [12])

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Fig. 8

Blade SS photos BE & AF 5 h of erosion (chordwise sections removed for clarity, airflow from left to right, scale: 1 mm per increment): bare 17-4PH steel (a) BE and (b) AF; TiN-coated (c) BE and (d) AF; CrAlTiN-coated (e) BE and (f) AF (adapted from Ref. [12])

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Fig. 9

Rear blade-tip photos BE & AF 5 h of erosion (airflow from left to right, scale: 1 mm per increment): bare 17-4PH steel (a) BE and (b) AF; TiN-coated (c) BE and (d) AF; CrAlTiN-coated (e) BE and (f) AF (adapted from Ref. [12])

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Fig. 10

Cumulative uncoated and coated blade assembly mass-loss during erosion testing (MaLE = 0.50, 2.5 g/(m3 of air) sand concentration (Hr No. 1-4), 4.0  g/(m3 of air) sand concentration (Hr No. 5))

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Fig. 11

TiN-coated blade SEM EDAX spectra (K-cnt versus energy in keV): (a) BE erosion and (b) AF 5 h of erosion (adapted from Ref. [12])

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