%0 Journal Article
%T Crack Healing in Mullite-Based EBC during Thermal Shock Cycle
%J Coatings | An Open Access Journal from MDPI
%D 2019
%R https://doi.org/10.3390/coatings9090585
%X Crack healing phenomena were observed in mullite and mullite + Yb 2SiO 5 environmental barrier coating (EBC) materials during thermal shock cycles. Air plasma spray coating was used to deposit the EBC materials onto a Si bondcoat on a SiC f/SiC composite substrate. This study reveals that unidirectional vertical cracks (mud cracks) formed after several thermal shock cycles; however, the cracks were stable for 5000 thermal shock cycles at a maximum temperature of 1350 ˇăC. Moreover, the crack densities decreased with an increasing number of thermal shock cycles. After 3000 thermal shock cycles, cracks were healed via melting of a phase containing SiO 2 phase, which partially filled the gaps of the cracks and resulted in the precipitation of crystalline Al 2O 3 in the mullite. Post-indentation tests after thermal shock cycling indicated that the mullite-based EBC maintained its initial mechanical behavior compared to Y 2SiO 5. The indentation load¨Cdisplacement tests revealed that, among the materials investigated in the present study, the mullite + Yb 2SiO 5 EBC demonstrated the best durability during repetitive thermal shocks. View Full-Tex
%U https://www.mdpi.com/2079-6412/9/9/585