|研究了DZ40M定向凝固钴基高温合金的钎焊行为，利用SEM/EDS对钎焊接头的微观组织形貌和物相组成进行了分析，并测试了接头的高温拉伸强度与高温持久寿命。结果表明，接头中间的钎缝组织主要由镍基固溶体与白色条状富W硼化物组成，靠近母材的元素扩散区主要由母材基体和分布在其中的块状硼化物组成，钎缝组织和元素扩散区之间的界面连接区主要由Ni-Co固溶体、灰色块状富Cr硼化物与弥散分布的富Co相组成。对接头的性能测试发现，在980 ℃下不同钎缝间隙的接头抗拉强度变化不大，抗拉强度约为150 MPa；而在980 ℃加载66 MPa条件下高温持久寿命随着钎缝间隙的增大而下降。高温持久寿命与钎焊中的硼化物析出相尺寸和含量有关，尺寸越大，含量越高，接头的高温持久寿命越低。
|关键词: 钴基合金 钎焊 显微组织 力学性能
|Microstructure and mechanical properties of the brazing joint for DZ 40 M cobalt - base superalloy
Chun Daoyong 1 , Wang Shiyang 2 , Sun Yuan 2 , Hou Xingyu 2 , Hou Guichen 2
|The brazing behavior of Co-base directionally solidified superalloy DZ40M was studied. The microstructure including typical precipitations of the joint were investigated by SEM equipped with EDS. The high temperature yield strength and stress rupture life of the joint were tested. Results showed that three distinct regions, including the filler alloy zone, interfacial bonding zone and element diffusion zone, can be found in the joint. The filler alloy zone consists of Ni-base solid solution and white strip-like W rich borides. Element diffusion zone adjacent to the base metal consists of granular borides and γ -phase from the base metal. The interfacial bonding zone, located between the filler alloy zone and diffusion zone, is composed of Ni-Co solid solution, gray block-like Cr rich borides and dispersed Co rich phase. The test results showed that tensile strength of joint was 150 MPa.With increasing the brazing seam width of the joint,the amount of content and size of the borides in the joint increased.High temperature tensile test and stress rupture life results indicated that the increase the brazing seam width can significantly reduce the high temperature stress rupture life,but the tensile strength is not significantly affected.
|Key words: cobalt-base superalloy brazing microstructure mechanical property