The Solidification Segregation and Homogenization Behavior of a New Solid-Solution Strengthened Ni-Based Superalloy: Key Effects of Zr Microalloying

Abstract

In this article, zirconium (Zr) microalloying plays a crucial role in regulating the solidification, segregation, and homogenization kinetics of a newly developed solid-solution strengthened Ni-based superalloy. Three alloy variants with distinct Zr contents (0.02, 0.08, and 0.22 wt%) are comprehensively analyzed using transmission electron microscopy, electron probe microanalysis, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The results show that Zr addition significantly widens the solidification temperature range ΔT (23, 26, and 36 °C), which aggravates interdendritic segregation of Zr, Mo, and Mn. Zr-rich MC carbides (0.036, 0.131, and 0.249 wt%) that precipitate at grain boundaries undergo progressive dissolution during homogenization at 1200 °C and are accompanied by an increase in the diffusion coefficients of elements (Cr: 4.99, 5.78, and 6.63 × 10⁻¹⁵ m² s⁻¹; Mo: 3.85, 5.31, and 6.55 × 10⁻¹⁵ m² s⁻¹). Consequently, an appropriate amount of Zr microalloying can facilitate elemental diffusion throughout the homogenization process. However, an excessive Zr addition will trigger severe elemental segregation during solidification, which has a detrimental impact on the hot workability of subsequent alloys. Finally, the synergistic effect is thoroughly discussed, and the optimal Zr content is determined.