Microstructural evolution of a Y2O3 network reinforced Ni–Co based superalloy fabricated by spark plasma sintering

Abstract

A Y2O3 network reinforced Ni–Co based superalloy was prepared by ball milling and spark plasma sintering (SPS). Ball milling time and solution treatment temperature were studied to obtain the best microstructure. Optical microscope (OM), scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA) were used to observe the microstructure evolution of as-sintered and solution-treated samples. Hardness also was conducted to analysis the variations of properties with the increase of solution-treatment temperature. The results revealed that the ball milling was beneficial to sintering activity of Ni–Co based superalloy powders. The Y-containing oxides in as-sintered alloys exhibited a network distribution. Master alloy with low C content made the microstructure more uniform during the sintering. After solution treatment at 1250 °C, the precipitations in the Y2O3 network reinforced Ni–Co based superalloy with low C content were fine nano tertiary γ′ phase with the size of ~30 nm. In the Vickers hardness test, Y-containing oxides provided additional hardness for the alloy. The appropriate solution treatment temperature and master alloy with low C content were beneficial to obtain better microstructure and properties of the alloy.