Effects of aging temperature and grain boundary character on carbide precipitation in a highly twinned nickel-based superalloy

ABSTRACT

The precipitation of carbides at grain boundaries in nickel-based superalloys and austenitic stainless steels can significantly affect the grain boundary related properties of the bulk material. This study evaluated the growth and dissolution of carbides in grain boundary engineering (GBE) treated nickel-based superalloy (Inconel 690) during aging treatment using scanning electron microscopy and transmission electron microscopy. The grain boundary network was stable during aging below 1000°C. At lower aging temperatures of 715 and 800°C, a small number of tiny carbide precipitates were observed on Σ3_c grain boundaries. In contrast, plate-like carbides precipitated near both sides of Σ3_i grain boundary and on one side of Σ9 grain boundary, and large carbide precipitates formed on Σ27 and random grain boundaries. At higher aging temperatures of 900 and 1000 °C, large carbide precipitates with a more consistent morphology precipitated at Σ9, Σ27, and random grain boundaries. Carbide dissolution was common during aging at these higher temperatures, which promoted the growth and redistribution of other carbides. These experimental findings provide valuable insights into the effect of aging temperature and grain boundary character on carbide precipitation behaviours.

KEYWORDS:

• Carbide precipitation
• carbide dissolution
• grain boundary character
• grain boundary engineering
• nickel-based superalloy

Acknowledgments

This work was financially supported by National Key Research and Development Program of China (No. 2016YFB0700401). The authors would like to thank Mr. Xirong Liu for the SEM observations.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also form part of an ongoing study.

Additional information

Funding

This work was financially supported by National Key Research and Development Program of China [grant number 2016YFB0700401].