Mechanical and thermal properties of calcium–magnesium aluminosilicate (CMAS) glass.

Thermal stability of a synthetic sand composition, which was developed as a simulant for calcium–magnesium aluminosilicate (CMAS) turbine deposits, was characterized using thermogravimetric and differential thermal analysis (TG/DTA). The sand was melted into CMAS glass, which had a composition of 23.3CaO–6.4MgO–3.1Al 2 O 3 –62.5SiO 2 –4.1Na 2 O–0.5K 2 O–0.04Fe 2 O 3 (mol.%), determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Bulk density of the glass was measured to be 2.63 g/cm 3 , and the Young's and shear moduli were 84.3 GPa and 33.6 GPa, respectively, along with a Poisson's ratio of 0.26. Vickers microhardness and indentation fracture toughness were determined to be 6.14 ± 0.1 GPa and 0.70 ± 0.05 MPa m 1/2 , respectively. Glass transition temperature, softening point and coefficient of thermal expansion of the glass were measured by dilatometry. Glass viscosities were estimated over a temperature range of 600–1500 °C using dilatometric reference points of the glass and from composition-based methods. Times required for infiltration of molten CMAS glass into thermal or environmental barrier coatings were also estimated. [ABSTRACT FROM AUTHOR]