Composition-dependent wetting and interfacial behavior of CMAS melts on YSZ thermal barrier coatings: a molecular dynamics and first-principles study

The corrosion of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) induced by molten calcium–magnesium–aluminosilicate (CMAS) deposits is closely related to interfacial wetting and diffusion behaviors. In this work, the effects of CMAS composition on the wetting and corrosion behavior of YSZ TBCs were investigated using molecular dynamics simulations combined with first-principles calculations. Single-component oxide melts (CaO, MgO, Al 2 O 3 , and SiO 2 ) and designed CMAS melts with varied compositions were constructed on the YSZ (010) surface to clarify the role of individual elements. The results show that CaO exhibits the lowest equilibrium contact angle (20.3°) and the highest diffusion coefficient, indicating a strong wetting and penetration tendency. For designed CMAS compositions, increasing Ca content leads to a continuous decrease in contact angle and an increase in adsorption work, with Ca 6 Mg 2 AlSi 6 O 22 showing the strongest interfacial adhesion. Electronic structure analysis reveals that the enhanced interfacial activity originates from strong interactions among Ca, O, and Y atoms near the Fermi level. These results provide atomic-scale insight into the composition-dependent wetting mechanisms of CMAS melts on YSZ surfaces within a simplified YSZ(010)-based model framework, and may offer theoretical guidance for improving CMAS resistance of thermal barrier coatings.