CMAS corrosion behavior of Ca2+xGd8-x(SiO4)6-x(PO4)xO2 ceramic materials

CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) will be melted and penetrated into the high-temperature protective coating exceeding 1200 °C, severely compromising its service life. Apatite-phase rare earth silicate, which often emerges as CMAS corrosion product, boasts exceptional thermophysical properties and shows significant promise for high-temperature thermal protection field. In this paper, two novel apatite materials Ca 2+x Gd 8-x (SiO 4 ) 6-x (PO 4 ) x O 2 (x = 1, 2) were synthesized via chemical co-precipitation and conducted CMAS corrosion tests at 1250 °C and 1350 °C, respectively. Results show that Ca 4 Gd 6 (SiO 4 ) 4 (PO 4 ) 2 O 2 readily reacts with CMAS, generating abundant Ca 3 (PO 4 ) 2 that bonds together, forming a protective barrier layer between the molten CMAS and the underlying ceramic material. The barrier layer is thickened by increasing corrosion time and remains stable over extended periods at 1250 °C. However, when the temperature rises to 1350 °C, the material severely degrades, and the corrosion products fail to form a Ca 3 (PO 4 ) 2 barrier layer. The Ca 4 Gd 6 (SiO 4 ) 4 (PO 4 ) 2 O 2 shows promise as a new thermal/environmental barrier coating ceramic material, offering resistance to CMAS corrosion at temperatures up to 1250 °C.