Interactions of Na2SO4 and yttrium-silicate environmental barrier coatings at 825 & DEG;C

Yttrium-silicates (Y2Si2O7 and Y2SiO5) are candidate environmental barrier coating (EBC) materials for silicon carbide ceramic matrix composites (SiC-CMCs). These materials' high-temperature, high-velocity steam, and siliceous debris resistance are well studied. However, Na2SO4-induced hot corrosion mechanisms are less understood. Free-standing atmospheric plasma sprayed Y2Si2O7 and Y2SiO5 coupons were exposed to 2.5 mg/cm(2) of Na2SO4 at 825 & DEG;C in 0.1% SO2-O-2 (g). Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry were used to identify a previously unknown damage mechanism. Water-soluble Y and Na-Y sulfates and oxysulfates formed in reaction with Na2SO4, causing significant damage to the yttrium-silicate EBCs materials.

Automated summary

Yttrium-silicates (Y2Si2O7 and Y2SiO5) are potential environmental barrier coating (EBC) materials for silicon carbide ceramic matrix composites (SiC-CMCs). While their resistance to high temperatures, high-velocity steam, and siliceous debris is well studied, the mechanisms of Na2SO4-induced hot corrosion are not fully understood. This study reveals a previously unknown damage mechanism in which water-soluble Y and Na-Y sulfates and oxysulfates react with Na2SO4, causing significant damage to the yttrium-silicate EBCs materials.