The effect of solidification rate on the solidified structure, solute segregation and microstructures such as carbide, γ'/γ eutectic, γ' phase and dendrite arm spacing was experimentally investigated employing a method of partially directional solidification and subsequent quick quenching. Three types of the solidified structure were identified: cellular, cellular-dendritic and developed dendrite-type, and the width of a mushy zone was narrowed when solidification rate increased from 2.5 µm/s to 125 µm/s. The carbide morphologies were affected by both solidified structure and solidification rate, it formed into bar-type in the cellular structure, and Chinese script-type in the dendrite structure. The increase of solidification rate caused a lot of γ'/γ eutectic and the change of γ' phase from cubic into cubic-round. The dendrite arm spacing decreased and the segregation of Cr, Al, Co, Mo, Ti was alleviated with increasing solidification rate.
(Received March 17, 1997)
Keywords: superalloy, solidification, microstructurePDF (Free) Table of Contents