Effects of Trace Impurities in Ni-Base Single Crystal Superalloys on High-Temperature Properties and Disablement of Impurities by CaO for Recycle of Superalloys

In determining the specifications for the production or recycling process of Ni-base single crystal superalloysNi-based single crystal superalloy, it is important to clarify the allowable trace impurityImpurity concentration. In this study, the effects of Pb and Sb on high-temperatureHigh temperature oxidation strength and oxidationOxidation resistance of 6th generation superalloySuperalloys TMS-238 were summarized. It was found that both Pb and Sb do not have a large effect on creepCreep rupture life, but they degrade oxidationOxidation resistance. The removal of impuritiesImpurity by melting in a CaOCaO crucible was tested and its mechanism was examined. It was found that Ca forms a compound with impuritiesImpurity within the alloy and prevents the segregationSegregation of impuritiesImpurity at the oxide film/substrate interface. The effect of CaOCaO was also confirmed in an experiment in which impurityImpurity S was removed from 1st generation Ni-base superalloySuperalloys TMS-1700 by adding CaOCaO particles in a 3-ton commercial melting furnace. Similar results were obtained for this alloy, where it was also found that CaS had formed inside the alloy, thus improving the oxidationOxidation resistance of TMS-1700.