DD5单晶高温合金钎焊接头的微观组织和力学性能分析

采用Co基钎料在1 180℃/60 min条件下钎焊DD5镍基单晶高温合金，利用SEM，EPMA分析接头的显微组织，讨论接头的焊缝间隙对显微组织和相分布的影响.结果表明，当钎焊间隙为10 μm时，焊缝组织与母材相似，由γ和γ'相构成，其中弥散分布着细小的M₃B₂相；随焊缝间隙的增加，焊缝中形成骨架状M₃B₂相，富钴的γ-Ni，Ni-Si化合物等脆性相；当焊缝间隙大于200 μm时，焊缝中间形成球状的钴基固溶体，在钴基固溶体之间分布着多种化合物相.对接头进行高温拉伸性能测试可知，随着钎焊间隙减小，接头的高温性能提高，接头在870℃的抗拉强度最高可达到792 MPa.

Microstructure and mechanical properties of DD5 single crystal superalloy brazing joint

Ni-based single crystal superalloy DD5 was brazed by using Co-based braze alloy at 1180℃ for 60 min. The microstructure of the joint and effect of the thickness of brazing seam on the microstructure and distribution of phases were investigated by SEM and EPMA in this research. The result indicates that the brazing seam was composed of γ+γ' and dispersive M₃B₂ precipitates when the thickness of seam is 10 μm, which is similar to substrates. With the thickness of brazing gap increasing, several kinds of compound were formed in the seam, which is the skeleton shaped M₃B₂ phase, γ-Ni solid solution rich Co, Ni-Si compounds and other brittle phase. When the brazing gap is over 200 μm, the spherical Co-based solid solution is formed in the brazing seam. Several kinds of compound are formed in the interface of Co-based solid solution. The testing results of mechanical properties show that the high temperature tensile of the joint improves with the decrease of brazing gap. The tensile of joint at 870℃ can reach the highest value of 792 MPa.