钎焊温度对CMSX-4单晶高温合金接头组织与性能的影响

采用一种镍基合金钎料钎焊CMSX-4单晶高温合金，利用扫描电镜、电子探针等分析手段研究接头的微观组织与相组成，并利用高温持久试验机测试接头的高温持久性能，讨论不同钎焊工艺条件下，接头的组织与性能变化规律及接头的断裂机制。研究发现，随着钎焊温度的提高，焊缝中低熔点化合物相减少，小尺寸凝固缺陷消失，白色硼化物比例先升高后降低，γ′沉淀相增多，接头的高温组织稳定性增加。当钎焊温度不低于1 290 ℃时，CMSX-4单晶高温合金接头在980 ℃/100 MPa条件下的持久寿命可达到400 h。观察接头的断口形貌发现，断裂均发生在焊缝处，断裂模式为以脆性断裂为主的混合断裂。

Effect of brazing temperature on microstructure and mechanical properties of CMSX-4 single crystal superalloybrazed 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 than 1 290 ℃, 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.