Influence of Refining and Vacuum-Breaking on Oxygen and Nitrogen Contents in Ni-Based Superalloy

After refinement,oxygen,nitrogen and inclusions contents of the Ni-based superalloy melted by vacuum induction were determined.The influences of the refinement and vacuum-breaking on the O,N contents and inclusions were researched.The results show that at the initial stage of refinement the oxygen reacts with carbon and produces CO,the degassing rate of the oxygen is high,but decreases at later stage.The degassing of nitrogen relies on the high temperature and vacuum.The degassing rate of the nitrogen is affected by the rate of CO's production and discharging.The O,N contents are related to the inclusion content in the alloy.There is a dynamic balance between element O in liquid metal and Al2O3 inclusion at high temperature during refining.The contents of oxygen,nitrogen and inclusions are all reduced and the Al2O3 inclusions in the alloy are decomposed with the refining time prolonged.