Pressure Infiltration of Molten Aluminum for Densification of Environmental Barrier Coatings

Abstract

\n Environmental barrier coatings (EBCs) effectively protect ceramic matrix composites (CMCs) from harsh engine environment, especially steam and molten salts. However, open pores inevitably formed during deposition process provide transport channels for oxidants and corrosives and lead to premature failure of EBCs. This work proposed a pressure infiltration densification method that blocked these open pores in the coatings. Results showed that it was difficult for aluminum to infiltrate spontaneously, but with the increase of external gas pressure and internal vacuum simultaneously, the molten aluminum obviously moved forward, but finally stopped infiltrating at a depth of a specific geometry. Based on the wrinkled zigzag pore model, a mathematical relationship between the critical pressure and the infiltration depth and the pore intrinsic geometry was established. Infiltration results confirmed this relationship, indicating that for a given coating, a dense thick film can be obtained by adjusting the internal and external gas pressures to drive the melt infiltration.