Preparation and structure control of a scalelike MoSi2-borosilicate glass coating with improved contact damage and thermal shock resistance

Abstract

The scalelike coatings with MoSi2 as emittance agent, flake fused quartz as coarse fillers, silica sol as dispersive medium of coating slurry, were prepared on rigid mullite fibrous ceramics to avoid fatal radial cracks and improve thermal shock resistance via combining slurry method with sol-gel method. And the particle size distribution of fused silica was changed to get different crack structure in scalelike coatings. Microstructure and phase composition of the coatings with different crack structure were investigated comprehensively. Contact damage resistance, thermal shock resistance and infrared radiating property were also studied. The results showed that only the coatings with mixing large and small particles of fused silica as coarse fillers could form crack network. The scalelike coatings with crack network went through 25 thermal cycles between 1500 °C and room temperature without peeling and spalling, and the bonding strength did not decrease after test. The scalelike structure with crack network also avoided radial cracks and exhibited some softness and less stiffness in Hertzian indentation test. The emissivity of coatings with different crack structure were all higher than 0.85; and the coatings with lower proportion of crack areas had higher emissivity.