Microstructure characteristics of FGH95 superalloy powders prepared by PREP

The microstructure characteristics of FGH95 superalloy powders prepared by plasma rotating electrode processing (PREP) have been investigated by using SEM. The relation between cooling rate and particle size of PREP FGH95 alloy powders has been calculated through numerical analysis based on Newtonian heat transfer formulation coupled with the classical heterogeneous nucleation. The results indicate that the solidification microstructures of particle surface are dendrite and cellular structures. With decreasing of the particle size, the microstructures of particle interior change from dendrite in major to cellular and microcrystal structures. The relation between droplet cooling rate and particle size can be expressed by T = 2.267 x 10(9)d(-1.649) during solidification. Thus, the relation of secondary arm space and cooling rate of FGH95 superalloy is concluded as S = 36.2T(-0.24).