Plasma forming multilayer ceramics for ultra-high temperature application

Multilayer ceramic coatings that incorporate mullite, yttria stabilized zirconia (YSZ) and ultra-high temperature zirconium diboride (ZrB2) are suited for thermal protection systems in rocket exhaust cones, insulating tiles for the space shuttle, engine components and ceramic coatings that are embedded into the windshield glass of many airplanes. The coatings were plasma sprayed simultaneously on roughened mild steel cylinder where ZrB2 was firstly deposited followed by mullite and YSZ coatings. A net-shape multilayer ceramic cylinder has been formed by chemical dissolution of the metallic cylinder in acidic medium. The net-shape multilayer ceramics can be simulated with metallic structure and used as a burner for a scramjet engine. The SEM micrographs showed the typical lamellar structure of plasma sprayed coatings. Cracks were evident at the lamella boundaries due to thermal stresses of ZrB2 and YSZ. ANSYS version 12.1 was used to perform the finite element analysis of the TBC. A theoretical modeling for the time to mullite melting at different heat fluxes (1, 1.5, 2, 2.5 W/mm2) was investigated.