Castable eutectic Ni–Ce high temperature alloys strengthened by γ/γʹ microstructure

Abstract

Ni-based superalloys are the premier material for high-temperature applications but are often difficult to manufacture via solidification-based processing. Eutectic alloys typically possess good castability due to narrow solidification ranges. The Ni–Ce system possesses a eutectic reaction but has never been examined as a potential high-temperature material. This work investigates the microstructure and mechanical properties of near-eutectic alloys Ni–17Ce and Ni–17Ce–5Al (wt.%). Both alloys show outstanding high-temperature microstructure and mechanical property stability at 900 °C. The formation of Ni3Al (γʹ) precipitates is observed in the primary FCC-Ni phase of the ternary Ni–Ce–Al alloy. The precipitation hardened ternary alloy exhibits superior hardness to Inconel 718 at elevated temperatures, retaining its strength to 750 °C, or about 50 °C higher than Inconel 718. The novel hierarchical microstructure consisting of thermally stable eutectic regions combined with γʹ-strengthened primary FCC-Ni and eutectic phases show great promise as a castable material solution for high-temperature applications.

Keywords

• Castable superalloy
• High-temperature applications
• Precipitation hardening
• Eutectic
• Thermal stability
• Hot hardness