Effect of initial powder particle size on the hot workability of powder metallurgy Ni-based superalloys

Abstract

The effect of the initial powder particle size on the hot workability of Ni-based superalloys was investigated. Herein, four powders with different particle size ranges (<53, 53–106, 106–150, and 150–500 μm) were prepared by sieving the same batch of gas atomized powder. It was found that the oxygen content of the powders decreased monotonically from 200 to ~50 ppm with increasing the particle size. The hot workability was evaluated by high-temperature tensile tests with different temperatures. The hot workability was found to be highly sensitive to the deformation temperature and was the highest at γ′ sub-solvus temperature of ~1100 °C. The initial powder particle size had a significant effect on the hot workability only at the peak temperature. The sample fabricated using the powder with relatively coarse particles (>106 μm) exhibited superior hot workability than that of the sample fabricated using the powder with finer particles (<53 μm). This was because of the high density of prior particle boundaries, which served as preferential cavity nucleation sites. These findings suggest that finer particles are not necessarily better with respect to the hot workability and provide novel insights into the powder metallurgy technology.