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使用电子束对DD407单晶高温合金进行焊接,采用光学显微镜和扫描电镜观察分析了熔凝区裂纹形态及分布特征,采用EDS测定了试样枝晶干与枝晶间区域的化学成分,计算了元素的偏析比并分析了裂纹形成原因。结果表明:在电子束热作用下,DD407单晶熔凝区中主要产生纵向裂纹、横向裂纹、弧坑裂纹、晶间裂纹,当其它工艺参数不变时,熔凝区凝固裂纹含量随着电子束流的增大先增大后减小;DD407单晶在焊接凝固过程中,杂晶区合金元素偏析严重,导致低熔点共晶组织聚集并形成低熔点液态薄膜,在凝固收缩拉应力作用下,使得杂晶区常形成凝固裂纹。
The electron beam was used to weld the DD407 single crystal superalloy. The morphology and distribution of cracks in the melting zone were observed by optical microscope and scanning electron microscope. The chemical composition of dendrite and dendrite was measured by EDS. Element segregation ratio and analyzed the cause of crack formation. The results show that the longitudinal cracks, transverse cracks, crater cracks and intergranular cracks mainly occur in the solidification zone of DD407 single crystal under the action of electron beam. When the other process parameters remain unchanged, the content of solidified crack in the melting zone decreases with the increase of electron The increase of beam current firstly increases and then decreases. During the solidification process of DD407 single crystal, the segregation of alloying elements in the miscellaneous zone is serious, resulting in the aggregation of low melting point eutectic and the formation of low melting point liquid film. , So that often the formation of heterogeneous crystalline solidified crack.