DD26单晶高温合金钎焊接头微观组织与力学性能研究

Microstructure and Mechanical Properties of Brazed DD26 Single Crystal Superalloy Joint

采用NiNbCoWCrAlSiMo钎料,在1225℃/30 min钎焊条件下开展了DD26单晶高温合金的钎焊试验,分析了0.05 mm、0.20 mm两种钎焊间隙对应接头的微观组织和性能。研究发现,接头组织主要由颗粒状的γ+γ′双相组织,以及分布在颗粒相之间的富W相和Ni–Nb(Si)相构成。当钎焊间隙为0.05 mm时,接头室温抗拉强度为614 MPa,达到DD26单晶合金的75.9%;1000℃抗拉强度为466 MPa,达到DD26单晶合金的78.8%;1000℃/75MPa条件下的持久寿命最高可达44.6 h。当钎焊间隙为0.20 mm时,接头室温抗拉强度为686 MPa,达到DD26单晶合金的84.8%;1000℃抗拉强度为479 MPa,达到DD26单晶合金的81.0%;1000℃/75 MPa条件下的持久寿命最高可达17.5 h。焊后热处理对间隙0.05 mm的接头持久性能影响不明显,间隙0.20 mm的接头持久性能在热处理后有所提升。断口分析发现,接头断裂表现出裂纹沿颗粒状的γ+γ'双相组织边缘扩展的特征。

The brazing of DD26 single crystal superalloy was investigated with NiNbCoWCrAlSiMofiller 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 ofγ+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 granularγ+γ′dual phase structure.