Crack-healing in ytterbium silicate filled with silicon carbide particles

A study on the influence of the silicate composition on the self-healing ability of a promising environmental barrier coating (EBC) material is reported. The EBC material consists of silicon carbide particles dispersed in a ytterbium silicate matrix. The composition of the silicate was varied from pure monosilicate to pure disilicate including a mixture of 50 vol-% of both phases. Pre-cracked specimens were mechanically tested before and after thermal annealing in air at 1400 °C accompanied by microstructural investigations. It is shown, that the self-healing mechanism is based on the application of compressive surface stresses due to graded oxidation of the SiC particles. With increasing amount of disilicate strength and self-healing ability increase.