Removal of inclusions from nickel-based superalloy by induced directional solidification during electron beam smelting

The electron beam smelting (EBS) is employed in refining the nickel-based superalloy. Removal efficiency of impurities and inclusions in nickel-based superalloy during EBS has been investigated. The morphology, microstructure and the content of oxygen in nickel-based superalloy before and after the experiment were analyzed. The EBS process is divided into three stages: melting stage, refining stage and solidification stage. The results show that the oxygen has been removed during the EBS process. The optimal experiment parameters are smelting power of 9 kW and smelting time of 30 min, by which a minimal evaporation loss of the alloy and a highest removal efficiency of impurities can be acquired. The removal efficiency of oxygen reaches 60% with the optimized experiment parameters. The inclusions are consist of oxides of aluminum, silicon and calcium and their composite oxides. The inclusions enrich at the circular region of the ingot periphery during solidification. A new method for preparation of nickel-based superalloy with high purity is found in the laboratory, and the enrichment mechanism of inclusion is analyzed.