对不同Re和W含量的铸态镍基单晶高温合金通过Brinell硬度计压痕变形, 分别在1230~1330 ℃保温1 h, 研究了难熔元素Re和W对合金再结晶行为的影响. 结果表明, 再结晶晶粒在压痕表面形成, 并沿枝晶干向内扩展, 晶界迁移受到枝晶间粗大γ'相和γ +γ'共晶阻碍. 添加Re和W提高了铸态单晶高温合金的γ'相溶解温度和γ +γ'共晶含量, 导致单晶高温合金的再结晶温度升高. 热处理温度升高, 各单晶高温合金的再结晶面积随着枝晶间γ'相和共晶含量的减少而增大. 相同热处理温度下, 由于不同成分单晶高温合金枝晶间粗大γ'相和γ +γ'共晶含量不同, 不含难熔元素Re和W的单晶高温合金再结晶面积最大, 含Re单晶高温合金的再结晶面积大于含W单晶高温合金, 同时添加Re和W的单晶高温合金再结晶面积最小.

Ni-based single crystal (SX) superalloys have been used as blades in aero-space industry and land-based applications due to their excellent high-temperature properties. However, residual strain is introduced into as-cast SX superalloy blades during the manufacturing process, such as casting, grinding or shot peening, and so on. Recrystallization (RX) occurs easily during subsequent high temperature heat treatment. In previous work, it is believed that RX has detrimental effect on the mechanical properties of SX superalloy. Furthermore, in order to improve the mechanical properties, more and more refractory elements, such as W, Re, Mo, Ta, are added into SX superalloys. However, so far, few reports about the effect of refractory elements on the RX in as-cast SX superalloys have been available. In the present work, the effect of Re and W on the RX behavior of as-cast Ni-based SX superalloy was studied. Single crystal superalloys with different Re and W contents were annealed at 1230~1330 ℃ after indened using Brinell hardnesstester. It is found that RX grains form at the surface under indentation and grow preferentially along the dendritic cores. Subsequent growth of RX is impeded by the residual coarse γ' and γ +γ' eutectics in the interdendritic regions. Both the volume fraction of γ +γ' eutectics and γ' solvus temperature are increased with the addition of Re and W, which are attributed to the increase of RX threshold temperature. For all SX superalloys studied in this work, RX area increases with the increase of annealing temperature due to the dissolution of γ' and γ+γ' eutectics. At the same annealing temperature, in comparison to Re, W shows more effect to inhibit RX growth. Additionally, SX superalloy containing both Re and W has the smallest RX area in the present experiments.