Effects of Different Cogging Technologies on the Inclusions in GH4738 Superalloy Produced by Double Vacuum Smelting

Cogging is a key part in the production process of superalloy, but inclusions affect the performance of superalloy. It is therefore particularly important to study the effects of cogging on the inclusions in superalloy. In our study, the superalloy GH4738 was made by double vacuum smelting. Cogging was performed by unidirectional drawing, upsetting and drawing, and upsetting/drawing with radial forging. The types and distributions of the inclusions after the three cogging processes were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and software such as Image Pro Plus. The results showed that double vacuum smelting essentially determined the types of the inclusions in the GH4738 superalloy. Four types of inclusions were found in the experiments: TiC-TiN-Mo-S composite, TiC-TiN composite, Ce-Mo-S composite, and SiC inclusions. In the case of cogging by unidirectional drawing, the average size of the inclusions first decreased and then increased, from the center to the edge. In the case of upsetting and drawing, and upsetting/drawing with radial forging, the average size of inclusions decreased from the center to the edge.