Effect of High Temperature Homogenization on Microstructure and Properties of GH4710 Nickel Base Alloy

Abstract

GH4710 nickel base alloy ingots， melted by VIM plus VAR， were subjected to trails of two-stage high-temperature homogenizing heat treatments， the microstructure and grain size of the ingots before and after heat treatment were analyzed by metallographic microscop. the distribution and content of alloy element in the ingot before and after heat treatment were evaluated by scanning electron microscope and electron probe， as well as to calculate the segregation index for alloying elements in different positions of ingots. Test result verified that， the two-stage homogenizing heat treatment at （1 150±50）℃×30 h-（1 200±10）℃×50 h， it could significantly eliminate the eutectic phase in the structure of GH 4710 ingot and reduce the element segregation in the ingot，and the mechanical properties of the forged bar are improved significantly. Under the test conditions of 980 ℃， 120 N/mm2， the persistence performance reached 126 h and 134 h， which was about double improvement compared with 53 h and 74 h of un-homogenizing heat treatment production. The persistent elongation rate has also increased by more than 50%.

Keywords

• gh4710 nickel base superalloy； eutectic phase； homogenizing heat treatment； dendritic segregation