Failure Prevention of Gas Turbine Blades Through Pack Aluminization

Mishra, R. K.; Kumar, Prashant; Muduli, S. K.

doi:10.1007/s11668-018-0498-1

Cited by 2 publications

(1 citation statement)

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“…Gas turbine blades are exposed to high-temperature corrosion and cyclical thermal loads, which lead to surface damage and thermomechanical fatigue [1,2]. The turbine components of the previous engine generations were protected against oxidation by diffusion aluminizing [3][4][5] and overlay metallic coatings [6,7]. Modern engines use multilayer Thermal Barrier Coatings (TBC), consisting of a metallic bondcoat and a ceramic thermal barrier, most commonly yttria-stabilized zirconia (YSZ).…”

Section: Introductionmentioning

confidence: 99%

Health and Durability of Protective and Thermal Barrier Coatings Monitored in Service by Visual Inspection

et al. 2022

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Protective and Thermal Barrier Coatings (TBC) applied on gas-turbine blades gradually degrade due to oxidation, aluminum depletion and impacts of environmental particles. Among various non-destructive coating testing methods (NDT), visual inspection can be undertaken regularly in service, but it provides little quantitative information, and only surface defects can be detected. This work aims at in-service monitoring of turbine blades with multilayer coatings applied by atmospheric plasma spraying (APS) in a few variants. They were validated during a series of accelerated mission tests of a retired military turbofan engine in a test cell together with five other technologies. The fifty-hour rainbow test focused on assessing coating durability. Between engine runs, 12 borescope inspections were conducted to monitor the health of the blades. Finally, the blades were disassembled and examined using computed tomography (CT) and metallographic methods. Throughout the testing, 31 newly-coated blades (66%) withstood the tests, producing results comparable to the reference blades. However, 16 blades suffered intolerable failures observed as increased roughness, gradual loss of the topcoat, spallation and minor foreign object damage. Visual inspection results were generally in agreement with subsequent laboratory tests.

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