Evolution of Aging Treatment Effect on the Microstructure and Hardness of a ‎Co-Al-W-Ti-Ta Based Superalloy ‎

Document Type : Original Research Article

Authors

1 M.Sc. Student‎, Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology,, Tehran,, Iran

2 Assistant Professor‎, Faculty of Materials and Manufacturing Technologies,, Malek Ashtar University of Technology, Tehran,, Iran

3 M.Sc., Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran

10.22034/frj.2020.232939.1119

Abstract

The aim of this study was to investigate the effect of temperature and time of aging on the microstructure and hardness of the novel Co-based superalloy with the composition of Co-7Al-7W-4Ti-2Ta. For this purpose, the new generation cobalt-based superalloy ingot cast by the VIM and VAR furnaces. Then aging treatment was performed at 700, 800 and 900°C for 8, 16 and 24 hours. Then, the specimens were cooled in air. Subsequently, the specimens were subjected to microstructural examinations by optical and electron microscopy and hardness test. The results showed that by increasing aging temperature from 700°C to 800°C, the γʹ precipitation and its growth occurred and its volume fraction and size increased. Therefore, the maximum hardness obtained for the specimen aged at 800°C. By increasing the temperature of aging to 900oC, the hardness decreased which was attributed to the precipitation of harmful β phase containing Co-Al-Ti and consumption of γʹ alloying elements results in reduction of the γʹ volume fraction.

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