Effect of slow cooling treatment on microstructure of difficult deformation GH4742 superalloy

For the difficult deformation of GH4742 superalloy, hot working of the γ + γ′ two phases region is inevitable. The dispersed small size γ′ phase markedly increases hot deformation flow stress and at the same time decreases the plasticity. In this paper, the effect of slow cooling treatment in γ + γ′ two phases region after homogenization on precipitation behavior of γ′ phase was evaluated. The relationships between grain boundary morphology, the size, morphology and distribution of γ′ phase and cooling rate were also investigated. The results showed that the little dendritic-type γ′ phase, γ matrix of lower solution strengthening effect and tortuous grain boundary after slow cooling treatment decreased the hot deformation flow stress of the GH4742 superalloy and increased hot deformation plasticity obviously.