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

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 degrees C. At lower aging temperatures of 715 and 800 degrees C, a small number of tiny carbide precipitates were observed on sigma 3(c) grain boundaries. In contrast, plate-like carbides precipitated near both sides of sigma 3(i) grain boundary and on one side of sigma 9 grain boundary, and large carbide precipitates formed on sigma 27 and random grain boundaries. At higher aging temperatures of 900 and 1000 degrees C, large carbide precipitates with a more consistent morphology precipitated at sigma 9, sigma 27, 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.

Automated summary

This study evaluated the growth and dissolution of carbides in grain boundary engineering (GBE) treated nickel-based superalloy during aging treatment, revealing different precipitation behaviors of carbides at various aging temperatures and grain boundary characters.