Durability of Dense Alumina Coating Deposited by Hybrid Aerosol Deposition under High-Speed Steam-Jet at Elevated Temperatures

抄録

In pursuit of achieving zero-emission power generation, the utilization of carbon-free fuels like H₂ holds promise for enhancing the reliability of the next-generation turbines. To realize the necessary of new operational environment, the implementation of dense environmental barrier coatings (EBCs) becomes essential. This study delves into the investigation of the durability of dense Al₂O₃ coatings deposited using the Hybrid Aerosol Deposition (HAD) method under the harsh condition of a high-speed steam-jet test, operating at approximately 125 m/s and elevated temperatures. The durability assessment encompasses uncoated SUS304 substrates and SUS304 substrates with dense HAD Al₂O₃ coatings deposited on one side. These samples underwent a rigorous 20-hour steam-jet test within a temperature range of 600–800°C.

Results indicate that the erosion rate of uncoated SUS304 substrates steadily increased with temperature, reaching a recession rate of 4.4 µm/h at the point of impingement. Conversely, the erosion rate was nearly halved following the deposition of HAD Al₂O₃ coating on one side of the substrates. The dense 8–9 µm Al₂O₃ coatings applied via HAD exhibited exceptional environmental protection during continuous exposure to the high-speed steam-jet at temperatures up to 800°C for 20 hours. Furthermore, the HAD layer effectively prevented oxygen penetration into the substrate. Post-test analysis revealed no significant features at the coating-substrate interface. Importantly, there were no alterations in the lattice parameter of Al₂O₃ crystal post-test. The coatings remained exclusively composed of the α-Al₂O₃ phase, with gradual crystallinity recovery driven by thermal effects during the steam-jet test and increasing temperature. These findings underscore the robust durability of HAD Al₂O₃ coatings in demanding high-speed steam-jet environments, making them a promising solution for enhancing power generation reliability.