Internal friction behavior of C/SiC composites with environmental barrier coatings in corrosive environment

Internal friction (IF, Q-1) behavior of C/SiC composites that were coated with two kinds of environment barrier coatings, scandium disilicate (Sc2Si2O7) and barium aluminosilicates (BaAl2Si2O8, BAS), were investigated in corrosive environments. The Sc2Si2O7-coated C/SiC composites were subjected to 50%H2O-50%O2 water vapor at 1400°C and BAS-coated C/SiC composites were exposed to molten Na2SO4 coupled with 50%H2O-50%O2 water vapor at 900°C. The values of Q-1 for the samples corroded at different times were recorded by means of a forced nonresonant technique. The weight loss and flexural strength as a function of corrosion time were measured. The microstructural evolution of the corroded specimens at different periods was also studied. The results indicate that the value of Q-1 of the coated C/SiC composites varies with their corrosion behaviors. The main factors that determine the IF behavior of the composites subjected to corrosion environments are the oxidation and corrosion of their fibers and interface. © 2010 The American Ceramic Society.