Effect of Al addition on oxidation behavior of Nb-based refractory alloys at elevated temperatures
| dc.contributor.author | Zhao, Yufei | |
| dc.contributor.department | Chalmers tekniska högskola / Institutionen för industri- och materialvetenskap | sv |
| dc.contributor.department | Chalmers University of Technology / Department of Industrial and Materials Science | en |
| dc.contributor.examiner | Guo , Sheng | |
| dc.contributor.supervisor | Li, Xiaolong | |
| dc.date.accessioned | 2024-11-18T12:27:43Z | |
| dc.date.available | 2024-11-18T12:27:43Z | |
| dc.date.issued | 2024 | |
| dc.date.submitted | ||
| dc.description.abstract | Improving gas turbine efficiency is closely linked to reducing global carbon emissions, which requires the development of materials that can operate at ultra-high temperatures. In this thesis, the oxidation behavior of three quaternary Nb-based refractory alloys, Nb-15Hf-5.5W-4Al, Nb-15Hf-5.5W-8Al, Nb-15Hf-5.5W- 12Al (nominal compositions, in at.%) is reported. The alloys were produced by vacuum arc melting, and the oxidation studies were performed at 800℃, 1000℃, and 1200℃ for 1h, 8h, and 24h, respectively, while the phase constitution, microstructure, and composition of oxidation products were analyzed by XRD, SEM, and EDS. Microstructures of three alloys all showed a single-phase bcc structure with a typical dendritic structure, and their Vicker hardness monotonously increased with the increasing Al content. The oxidation products contained different complex oxides including Nb2O5, Hf6Nb2O17, AlNbO4, WO3, and Nb11AlO29. At 800℃, the oxidation behavior was linear, but at higher temperatures, the oxidation behavior was more parabolic. Although oxide layers and transition layers were seen to form in samples after oxidation at 1000℃ and 1200℃, all formed oxide layers were not protective, and consequently, pesting was observed almost in all cases, except the condition of oxidation at 800℃ for 1h. The results showed that adding Al up to 12 at.% helped to improve the oxidation resistance of these Nb-based refractory alloys, but the improvement was still limited and importantly it was not capable of forming a dense and protective oxide layer yet. | |
| dc.identifier.coursecode | IMSX30 | |
| dc.identifier.uri | http://hdl.handle.net/20.500.12380/308990 | |
| dc.language.iso | eng | |
| dc.setspec.uppsok | Technology | |
| dc.subject | Refractory alloys | |
| dc.subject | Nb-based alloys | |
| dc.subject | Oxidation resistance | |
| dc.subject | Pesting | |
| dc.subject | Microstructure | |
| dc.title | Effect of Al addition on oxidation behavior of Nb-based refractory alloys at elevated temperatures | |
| dc.type.degree | Examensarbete för masterexamen | sv |
| dc.type.degree | Master's Thesis | en |
| dc.type.uppsok | H | |
| local.programme | Materials engineering (MPAEM), MSc |