| Author: | Xu, Pengyu |
| Title: | Nanoscale precipitation and mechanical properties of γ’-strengthened cobalt-based superalloys |
| Advisors: | Jiao, Zengbao (ME) |
| Degree: | M.Sc. |
| Year: | 2023 |
| Subject: | Heat resistant alloys Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | 39 pages : color illustrations |
| Language: | English |
| Abstract: | Cobalt-based superalloys have been widely used in aircraft turbines for vane and combustor sections, due to their high specific strength, excellent corrosion resistance, and superior heat resistance. High performances superalloys can improve the efficiencies of turbine engines and play a significate role in environment pretention. In this work, a novel γ′-strengthened cobalt-based superalloys (Co‒16Cr‒7Ti‒1Ta‒0.4B) with high thermal stability and outstanding mechanical properties was developed and the formation, mechanical properties, and thermal stability mechanisms were systematically investigated through a combination of scanning electron microscope (SEM), energy dispersive spectroscope (EDX), X-ray diffraction (XRD) and tensile test. The new alloy has an excellent yield strength of 700 MPa, ultimate tensile strength of 858 MPa, and a super ductility of 25% at 800 °C. The XRD and SEM results reveal that a high number density of γ′-Co3(Ti, Ta) nano-precipitate are uniformly precipitate in the matrix at 800 °C, which play the most strengthen effect on the strength. When aging at 900 °C for long time, micro scale Laves phase-Co2(Ti, Ta) is formed at grain boundary, which furtherly enhances the strength of the alloy but slightly decreases the ductility. This alloy exhibits a promising combination of high strength, thermal stability, and acceptable ductility, making it a potentially valuable material for various high-temperature applications. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 7482.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 2.2 MB | Adobe PDF | View/Open |
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