Abstract:Nickel base single crystal superalloys are widely used to fabricate turbine blade materials, since they have high temperature capability, excellent mechanical and environmental properties. Appropriate heat treatment process can improve alloy performance by changing its microstructure. The second generation single crystal alloy CMSX-4 was prepared by screw selecting method and low segregation technology. The homogenizing heat treatment carried out in an antivacuum chamber oven and followed by air cooling (AC), in order to investigate the effect of heat treatment on microstructure and stress rupture properties. The results show that elemental segregation of alloy is obviously improved after multistage solid solution heat treatment 1280 ℃, 1 h+1290 ℃, 2 h+1300 ℃, 6 h AC+1140 ℃, 4 h AC+870 ℃, 16 h AC (process 1). The rupture life of the alloy is 207.50 h under the condition of 980℃/250MPa and 280.84 h under the condition of 1070℃/140MPa. During heat treatment, homogenization micropores formed in the solution process and the size of solidification micropores increased. These micropores are the weak and crack initiation points during the creep tests of the alloy. Elemental segregation of the alloy was also improved after over melting point heat treatment heat treatment 1320℃, 3 h AC+1140℃, 4 h AC+870℃, 16 h AC (process 2). It can be concluded that the homogenization effect of process 2 is not as good as that of process 1 by measuring the segregation coefficient. However, the rupture property performs well and the rupture life of the alloy is 293.08 h under the condition of 980℃/250MPa and 310.10 h under the condition of 1070℃/140MPa. The solid solution time of process 2 is shorter and the number of micropores is less.