As the inlet temperature of engines increases, injected sand, volcanic ash, and dust melt to form calcium−magnesium−aluminosilicate (CMAS) glass, which subsequently adheres to the surface of ytterbium monosilicate (YbMS; Yb₂SiO₅) environmental barrier coatings (EBCs), posing a serious degradation threat. In this study, a novel aluminum surface modification strategy was proposed to prevent direct interaction between the coatings and CMAS, thereby increasing corrosion resistance. The modification confers a dual-protection mechanism: First, it seals exposed interconnections deposited by air plasma spray (APS) and facilitates the in situ formation of a dense, continuous ytterbium aluminum garnet (YbAG; Yb₃Al₅O₁₂) layer, serving as the primary, nonreactive physical barrier against CMAS infiltration; second, it inhibits silica consumption by YbMS while releasing silica into the melt. This process increases the melt viscosity, fundamentally suppressing CMAS penetration. The combined effect of these mechanisms extends the coating life by at least 10 times. Although the CMAS resistance of unmodified YbMS is inferior to that of previous ytterbium disilicate (YbDS; Yb₂Si₂O₇) coatings, aluminum-modified YbMS has significantly greater resistance than modified YbDS. This performance reversal is attributed to the unique microstructure of YbMS, which favors the formation of a higher-quality, more protective YbAG layer, thereby fundamentally altering the CMAS interaction mechanism.

Environmental barrier coatings (EBCs) effectively protect the ceramic matrix composites (CMCs) from harsh engine environments, especially steam and molten salts. However, open pores inevitably formed during the deposition process provide the transport channels for oxidants and corrosives, and lead to premature failure of EBCs. This research work proposed a method of pressure infiltration densification which blocked these open pores in the coatings. These 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, and finally stopped infiltrating at a depth of a specific geometry. Based on the wrinkled zigzag pore model, a mathematical relationship between the critical pressure with the infiltration depth and the pore intrinsic geometry was established. The 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 a melt infiltration.