By applying a small punch testing technique, it has been previously shown that near-surface aluminized CoCrAlY coatings of unused advanced gas turbine blades had very low ductility due to the formation of Al and Cr rich phases, compared to internal and near-interface regions. Thus, it is important to examine how in-service operation affects the mechanical properties of the internal, near-interface coatings and substrates to maintain the integrity of gas turbines. This study attempts to compare the effects of in-service operation for 20,000 h under combustion of liquefied natural gas and thermal ageing in air. The in-service operation led to a larger ductility loss in concave coatings near the tailing edge, although the ductility slightly improved above testing temperature at 950 °C. Substrate used in-service had lower ductility at 950 °C than the used concave coatings. The ductility of used internal coatings depended on the blade location. In convex coatings near the leading edge, in-service degradation was not significant and the ductility was about two-fold greater than in the thermally aged blade. The in-service degradation mechanism of the aluminized CoCrAlY coatings is discussed in light of the operating temperature distribution and microstructural evolution.
- International Gas Turbine Institute
Ductility Loss in Aluminized CoCrAlY Coatings Exposed to In-Service Environment
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Shinohara, N, Ito, A, Sugiyama, K, Sugita, Y, Kameda, J, Bloomer, TE, & Sakurai, S. "Ductility Loss in Aluminized CoCrAlY Coatings Exposed to In-Service Environment." Proceedings of the ASME Turbo Expo 2001: Power for Land, Sea, and Air. Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award. New Orleans, Louisiana, USA. June 4–7, 2001. V004T01A004. ASME. https://doi.org/10.1115/2001-GT-0416
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