Inclusions in wrought superalloys: a review

Inclusions in wrought superalloys significantly affect the stability of the alloy properties and limit their use and development in aeroengines and other applications. The types and sources of inclusions in wrought superalloys were reviewed with analysis of the conditions of inclusion formation from the viewpoints of thermodynamics and kinetics. The thermodynamic data for inclusion formation in nickel-based and cobalt-based alloys were summarized and improved. The damage of inclusions to the fatigue and tensile properties and workability of these alloys and the mechanisms of crack initiation and propagation caused by inclusions were also discussed, and the effects of inclusions with different characteristics on crack propagation were reviewed. In addition, the control methods and mechanisms of inclusions in the triple smelting process (vacuum induction melting + protective electroslag remelting + vacuum arc remelting) were covered, providing a reference for improving the control technology of inclusions in wrought superalloys. Finally, the difficulties and development trends for inclusion control in wrought superalloys were discussed.