Pore filling behavior of YSZ under CMAS attack: Implications for designing corrosion‐resistant thermal barrier coatings

To understand the pore filling behavior in thermal barrier coatings during calcium‐magnesium‐alumino‐silicate ( CMAS ) infiltration process, porous yttria‐stabilized zirconia pellets with different sizes of spherical pores were prepared to simulate thermal barrier coatings. The pores (D50 ranging from 6 to 77 μm) were introduced to the pellets using poly methyl methacrylate as pore forming agents. Then the pellets were sintered to remove the pore forming agents and to achieve a similar volume fraction of porosity with thermal barrier coatings. After CMAS infiltration, only some small pores in the CMAS ‐infiltrated zones were filled by CMAS , whereas all large pores (larger than 13 μm) remained unfilled; besides, the results also show that even open pores can resist filling by CMAS . The reason may relate to pore diameters; if the diameter of a pore is relatively large, the pore surface will not be completely wetted by liquid CMAS , the liquid meniscus will be discontinuous, and therefore the pore cannot be filled. The key insight gained from this study is that introducing “ CMAS ‐proof” pores into thermal barrier coatings may be a potential way to mitigate CMAS damage.