The Influence of Segregation Bands and Hot Rolling on the Precipitation of Secondary Phases during Aging at 750 °C for Nickel Alloy 625

Abstract

For Inconel 625, where the γ” and δ phases precipitate, the influence of prior hot rolling on the process is not well covered. The influence of segregation bands and prior hot rolling on the precipitation of secondary phases during aging at 750 °C for different times was investigated. Prior hot-rolling was conducted on a hot rolling mill at 1050 °C and 1150 °C with three different deformation levels. The hot rolled samples were aged at 750 °C for 1, 5, 25 and 125 h. The γ″ precipitated in both the deformed and recrystallized grains in the segregation bands containing a high concentration of niobium and molybdenum and a lower concentration of nickel, chromium and iron. The opposite was observed between the segregation bands where no γ″ precipitate was found. There was a smooth transition in the density and the size of the γ″ particles in the deformed grains at the border of the segregation bands, while a more complex transition occurred in the recrystallized grains. This occurred in the area where the average niobium concentration decreased from 4.5 to 2.7 wt. %, which influenced the mechanical properties.

Keywords

• nickel-based superalloy
• hot rolling
• recrystallization
• segregation
• precipitation