Microstructure evolution and mechanical behavior of Ni-based single crystal superalloy joint brazed with mixed powder at elevated temperature
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2017年第10期
论文作者：Guanglei Wang Yuan Sun Xinguang Wang Jide Liu Jinlai Liu Jinguo Li Jinjiang Yu Yizhou Zhou Tao Jin Xudong Sun Xiaofeng Sun
文章页码：1219 - 1226
摘 要：Brazing of a Ni-based single crystal superalloy has been investigated with the additive Ni-based superalloy and filler Ni–Cr–W–B alloy at 1260℃, and attentions were paid to the microstructure evolution during brazing and the stress-rupture behavior at 980℃ of such brazed joints after homogenization. Microstructure in the brazed joint generally includes brazing alloy zone（BAZ）, isothermally solidified zone（ISZ） and diffusion affected zone（DAZ）. Microstructure evolution during this brazing process is discussed at the heating stage, the holding stage and the cooling stage respectively, according to the diffusion path of B atoms. Initially well-distributed γ’/γ’ microstructure in the homogenized bonded zone after heat treatment and substantial γ’ rafts enhance the post-brazed joint to obtain a stress-rupture lifetime of more than 120 h at 980℃/250 MPa. On the other hand, the decreased stress-rupture behavior of post-brazed joint, compared with parenting material, is ascribed to the presence of inside brazing porosity and stray grain boundary, which not only reduces the effective loading-carrying area but also offers preferential sites for creep vacancy aggregation to further soften stray grain boundary. And finally an early fracture of these post-brazed joints through the intergranular microholes aggregation and growth mode under this testing condition was observed.
Guanglei Wang1,2，Yuan Sun1，Xinguang Wang1，Jide Liu1，Jinlai Liu1，Jinguo Li1，Jinjiang Yu1，Yizhou Zhou1，Tao Jin1，Xudong Sun2，Xiaofeng Sun1
1. Institute of Metal Research, Chinese Academy of Sciences2. School of Materials Science and Engineering, Northeastern University
摘 要：Brazing of a Ni-based single crystal superalloy has been investigated with the additive Ni-based superalloy and filler Ni–Cr–W–B alloy at 1260℃, and attentions were paid to the microstructure evolution during brazing and the stress-rupture behavior at 980℃ of such brazed joints after homogenization. Microstructure in the brazed joint generally includes brazing alloy zone（BAZ）, isothermally solidified zone（ISZ） and diffusion affected zone（DAZ）. Microstructure evolution during this brazing process is discussed at the heating stage, the holding stage and the cooling stage respectively, according to the diffusion path of B atoms. Initially well-distributed γ’/γ’ microstructure in the homogenized bonded zone after heat treatment and substantial γ’ rafts enhance the post-brazed joint to obtain a stress-rupture lifetime of more than 120 h at 980℃/250 MPa. On the other hand, the decreased stress-rupture behavior of post-brazed joint, compared with parenting material, is ascribed to the presence of inside brazing porosity and stray grain boundary, which not only reduces the effective loading-carrying area but also offers preferential sites for creep vacancy aggregation to further soften stray grain boundary. And finally an early fracture of these post-brazed joints through the intergranular microholes aggregation and growth mode under this testing condition was observed.
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