About this Abstract |
Meeting |
Superalloys 2024
|
Symposium
|
Superalloys 2024
|
Presentation Title |
E-15: The Effect of Ti Replacement with Nb on the Long-term Oxidation Behaviour at High Temperatures of Ni-base Superalloys for Turbine Disc Applications |
Author(s) |
Ana Carolina B. Silva, Nabil Chaia, Satoshi Utada, Luciano Braga Alkmin, Gilberto Coelho, Yuanbo T. Tang, Roger Reed, Carlos Angelo Nunes, Phani Karamched |
On-Site Speaker (Planned) |
Carlos Angelo Nunes |
Abstract Scope |
This work focuses on the effect of partial and total replacement of Ti with Nb on the long-term oxidation at 800 °C up to ~2000 h of Ni-based superalloys for turbine disc applications. The replacement of Ti with Nb leads to a lower mass gain of the specimens, in both pseudo and isothermal oxidation conditions. The alloys presented a relatively smooth oxide scale surface; however, the roughness of the Nb-free/high-Ti alloy is twice of that of the Ti-free/high-Nb alloy. From XRD data, the Nb-free/high-Ti alloy presented Cr2O3, TiO2, Al2O3, (Ni,Co)Cr2O4 and γ+γ' (matrix) phases, while the Ti-free/high-Nb alloy presented Cr2O3, Al2O3, (Ni,Co)Cr2O4, γ+γ' (matrix) and δ-Ni3Nb phases. The chromia layer thickness of the Ti-free/high-Nb alloy ranged from 1.0 to 1.5 µm, the thinnest among all the alloy for any given oxidation time and condition, with no mass change after approximately 280 h exposure. The exceptional oxidation behavior is attributed to the absence of Ti in this specific alloy composition. The semi-continuous alumina formation underneath the chromia scale as well as the formation of δ-Ni3Nb phase filling up the spaces between the alumina intrusions are probably the reason of delayed outward Cr diffusion. |
Proceedings Inclusion? |
Definite: At-meeting proceedings |