Thermodynamics calculation and analysis of oxide inclusion formation in single crystal superalloy DD6

Calculation and analysis on the thermodynamics conditions for the formation of oxide inclusion during the vacuum induction melting of Ni-based single crystal superalloy DD6 have been carried out by using Thermo-calc thermodynamics software and JMatPro analysis software. The results show that the main oxide inclusion is Al₂O₃. Under the thermodynamic equilibrium state, the value of oxygen activity during the melting and solidification stages is within (3.21-14.0)×10^-7 and (1.63-4.89)× 10^-8. It will cause increasing oxygen in the molten liquid and the formation of Al₂O₃ inclusion by using CaO crucible when the vacuum level is 0.lPa. In order to make the content of Al₂O₃ inclusion reduce to less than 10×10^-6, it is necessary to control oxygen content below 4.709×10^-6 before alloying treatment.