Optical absorption effects in thermal radiation barrier coating materials

• Published in: Surface & coatings technology Vol. 487; p. 130974
• Main Authors: Koutsakis, Georgios, Clarke, David R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2024
• Subjects: Gas turbine engine; Optical absorption; Propulsion materials; Thermal barrier coating; Thermal radiation; Propulsion materials; Thermal radiation; Optical absorption; Gas turbine engine; Thermal barrier coating
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.130974

Future gas turbine engines will operate at higher gas temperatures and consequentially hot-section components such as blades, vanes and combustors, will be subject to higher thermal radiation fluxes than today. Current thermal barrier coating materials are translucent over the spectral region of the heat flux so future coatings will also have to provide a barrier to thermal radiation. The effects of optical absorption and scattering properties of coating materials on the temperatures and heat fluxes through coatings are explored using a two-flux heat transfer model, and promising combinations are identified that reduce the coating–alloy interface temperatures. Lower interface temperatures occur for thickness normalized absorptions of κ¯L>1. The effect of both a narrow and a broad band spectrally selective absorbing Gd2Zr2O7 based coating materials are then studied. These show that large values of the product of the normalized absorption length and the spectral width of the absorption are required to significantly decrease the radiative heat transport through a coating. The results emphasize the importance of enhancing the optical absorption of the next generation barrier materials as a strategy to increase gas turbine engine efficiency by decreasing compressor bleed air cooling requirements. •Explores effects of optical absorption and scattering in coating materials using a two-flux model.•Identifies coating materials combinations that reduce coating–alloy interface temperatures.•Analyzes the impact of spectrally-selective absorbers like rare-earth doped gadolinium zirconate.•Demonstrates the importance of enhanced optical absorption for increasing gas turbine efficiency.•Discusses broad band absorbers and their potential in improving thermal barrier coatings.