The brazing of DD26 single crystal superalloy was investigated with NiNbCoWCrAlSiMo filler metal under the condition of 1225 ℃/30 min. Microstructure and mechanical properties of joint corresponded to brazing gaps of 0.05 mm and 0.20 mm were analyzed. It was indicated that the joint microstructure was composed of γ+γ′ particles and W-rich and Nb-rich phases distributed among the particles. When the brazing gap was 0.05 mm

the joint tensile strength at room temperature was 614 MPa

about 75.9% of DD26 alloy; the joint tensile strength at 1000 ℃ was 466 MPa

about 78.8% of DD26 alloy; and the creep rupture life under the condition of 1000 ℃/75 MPa was 44.6 h. When the brazing gap was 0.20 mm

the joint tensile strength at room temperature was 686 MPa

about 84.8% of DD26 alloy; the joint tensile strength at 1000 ℃ was 479 MPa

about 81.0% of DD26 alloy; the creep rupture life under the condition of 1000 ℃/75 MPa was 17.5 h. The influence of heat treatment on the creep rupture life of joint with brazing gap of 0.05 mm was insignificant

while that of joint with brazing gap of 0.20 mm increased. The fracture analysis showed that the joint fracture presented the characteristics of crack propagation along the edge of granular γ+γ′ dual phase structure.