Abstract
Detailed microstructural characterisation of phases present in a next generation polycrystalline Ni based superalloy after thermal exposure at 900 °C was carried out, focusing on carbides and borides. Metastable M5B3 precipitated after 32 h had a stoichiometry of (Cr0.7Mo0.2W0.1)5B3 with substitutions with Ni, Co, Nb and Ta. Fine M23C6 (a = 10.62 Å) was overgrown by metastable M5B3, as shown by rigorous TEM-SAD pattern investigation. The borides were eventually dominated by Mo rich M3B2, at the apparent expense of MC. Decomposition of MC was confirmed; it transformed sequentially to γ and then γ΄. The primary driving force for the MC decomposition was attributed to γ΄ precipitation, increasing its fraction to the thermodynamic equilibrium at 900 °C.
Original language | English |
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Article number | 113721 |
Journal | Materials Characterization |
Volume | 209 |
Early online date | 1 Feb 2024 |
DOIs | |
Publication status | Published - 1 Mar 2024 |
Bibliographical note
AcknowledgementThe joint support of UK Engineering and Physical Science Research Council (EPSRC) and Rolls-Royce plc is greatly acknowledged. HSK and LS would like to thank Centre for Electron Microscopy (CEM) and Metallurgy&Materials Characterisation Facility at University of Birmingham for the support throughout the experimental investigations.
Keywords
- Superalloys
- Iso-thermal treatment
- Carbides: MC M23C6
- Borides: M5B3 M3B2
- TEM
- EDS
- Thermo-Calc software