EFFECT OF EXTENT OF HOMOGENIZATION ON THE HOT DEFORMATION RECRYSTALLIZATION OF SUPERALLOY INGOT IN COGGING PROCESS postprint

Abstract: The elimination of the segregation improves the thermo plasticity of superalloy ingot during the homogenization process, but coarser grain structure and high-temperature oxidation caused in further homogenization have an adverse impact on the thermo plasticity. The inheritance of coarse grain structure in the followed hot working process increases the tendency of cogging crack and makes the grain refining harder, leading to a lower yield of the final workpiece. The microstructure characteristics and their hot deformation behaviors of GH4740H, GH4738, GH3625 and 690 alloys under different homogenizations were investigated by means of microstructure analysis methods and crack propagation testing. The experimental results show that the reasonable homogenization processing needs to take into account the segregation elimination arising thermo plasticity addition, more to consider grain coarsing and severe oxidation leading to decrease plasticity. Based on the residue dendrites can provide more recrystalazation nucleation sites, the partial homogenization possessing probably exists rationality. This research work provides an exploratory study for the improvement of the homogenization-cogging process of superalloy.