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以厚度≤1 mm的Cr,Ni混合粉做中间层,在焊接温度为1650℃,真空度(3.0～4.0)×10-2 Pa,保温时间1～2 h,加压0.1 MPa条件下对钼和石墨进行扩散焊接。通过扫描电子显微镜观察焊接试样接口组织形貌,用其附带的能谱仪进行化学成分分析,用X射线衍射仪进行物相分析。并分析焊接过程中的界面反应,认为实验条件下的焊接过程与瞬间液相扩散焊(TLP)焊接机制相一致,包括中间层的熔化(或溶解)、母材溶解和迁移、等温凝固、固相成分均匀化4种相变过程,靠近母材部分界面反应遵循快速通道扩散机制,整个焊接层组元浓度梯度与薄膜源扩散模型相一致。中间层与母材元素反应形成的最终产物包括Cr3C2,Cr7C3及Mo2C等Ni以单质形式弥散其中,最终形成不同成分粒状组织,一定程度上阻止了脆性相中的裂纹扩展。石墨基体中也明显有含合金元素的新相生成,有利于实现基体与中间层的连接。
The Cr and Ni mixed powder with the thickness of less than or equal to 1 mm was used as the intermediate layer. Under the condition of the welding temperature of 1650 ℃, the degree of vacuum of 3.0 ~ 4.0 × 10-2 Pa, the holding time of 1 ~ 2 h and the pressure of 0.1 MPa, And graphite diffusion welding. Scanning electron microscope (SEM) was used to observe the microstructure of the interface of the welded specimens. The chemical composition of the welded specimens was analyzed by using the attached energy dispersive spectrometer. The phase analysis was carried out by X-ray diffractometer. And analyzed the interface reaction during the welding process. It is considered that the welding process under the experimental conditions is consistent with the TLP welding mechanism, including the melting (or dissolution) of the middle layer, the dissolution and migration of the base metal, isothermal solidification, solidification Phase composition of the four phase transformation process, part of the interface near the base metal follow the fast channel diffusion mechanism, the entire weld layer concentration gradient consistent with the film source diffusion model. The final products formed by the reaction of the intermediate layer with the base metal include Ni, such as Cr3C2, Cr7C3 and Mo2C, dispersed therein in the form of simple substance and finally formed granular structures with different compositions, to a certain extent, the crack propagation in the brittle phase was prevented. Graphite matrix also obviously contains new alloying elements formed, is conducive to the connection of the substrate and the middle layer.