Effect of brazing temperature on microstructure and mechanical properties of CMSX-4 single crystal superalloy brazed joint

The single crystal superalloy CMSX-4 was brazed with a Ni-based filler alloy,the microstructure and the phase composition were studied by scanning electron microscopy（ SEM）,electron probe microanalysis（ EPMA）. The stress rupture property of joint was tested by high temperature stress rupture property testing machine. The result shows that the fracture mechanism and stress rupture property at high temperature of joint transformed with the different brazing temperature. With the increase of brazing temperature,the low melting point eutectic phase and the solidification defect with small size disappears,the proportion of white boron compounds increases firstly and then decreases. Besides,the amount of the precipitated phase and the high temperature structure stability of joint increase. When the brazing temperature is not lower than1 290 ℃,the rupture life of CMSX-4 superalloy under the condition of 980 ℃/100 MPa reaches up to 400 h. The fracture morphology of joints shows that all the fractures occurred at the weld seam. The fracture mode of joint is the mixed fracture characterized by brittle fracture.