An aluminum surface modification strategy for enhancing CMAS corrosion resistance of environmental barrier coatings

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.