The effect of refining time and calcium addition on the removal of oxygen, nitrogen, and hydrogen from IN713LC during vacuum induction refining

This research was intended to decrease the gas content, namely, oxygen, nitrogen, and hydrogen, in the nickel-based superalloy IN713LC using vacuum induction refining (VIR) and calcium addition. To accomplish this, the molten superalloy was subjected to individual VIR for up to 15 min, as well as a combination of VIR and calcium addition up to 0.03 wt%. Then the removal of oxygen, nitrogen, and hydrogen through the superalloy's constituent carbon and added calcium was investigated. The results showed that with increasing refining time and calcium content, total oxygen and nitrogen levels decreased continuously according to second-and first-order kinetic models, respectively. However, the addition of 0.03 wt% Ca resulted in the lowest concentration of total oxygen, and a refining time of 15 min resulted in the lowest concentration of total nitrogen and hydrogen. The remaining air in the crucible's unfilled crevices was proposed as the reason for the need for calcium addition to achieve greater oxygen removal than the carbon deoxidation process. In addition, the influence of calcium addition on the removal of Al2O3 inclusions as one of the probable mechanisms of total oxygen decrease was discussed using the phase stability diagram of the Al2O3-CaO inclusion system, which was constructed in the current study.