Carbide precipitation behavior during vacuum arc remelting of GH4742 alloy

Abstract

The different heat transfer conditions in each region of the vacuum arc remelting superalloy ingot lead to significant difference in the morphology and size distribution of carbide in the ingot. Based on industrial vacuum arc remelting GH4742 alloy as a raw material, using metallographic and scanning electron microscopic analysis quantitative analysis method to study the ingot different position distribution of the carbide precipitation behavior and microstructure, supplemented by MeltFlow-VAR simulation software, the solidification process of remelting different cooling rate and local solidification time on the influence of carbide were analyzed. The results show that Nb and Ti elements are enriched in the carbide precipitates of GH4742 alloy, and the segregation degree of Nb element is the largest. The area of the precipitated phase is decreased from the center to the edge, and the morphology is changed from skeleton-like and cursive to interconnected fine strips. As the cooling rate increases, the dendrites become more slender and compact, and the dendrite spacing decreases. The area of precipitated phase is linearly related to the secondary dendrite spacing. Increasing the cooling rate can reduce the dendrite spacing, thus the area of precipitated phase is reduced effectively.

Keywords

• vacuum arc remelting
• gh4742
• carbide
• dendrite spacing
• meltflow-var