Environmental/thermal barrier coating system with silica diffusion barrier layer

摘要

Improved adhesion of thermal barrier coating systems to nonmetallic substrates using a layer of silica on an underlying nonmetallic substrate that includes a silicon containing material is described. The improved adhesion occurs because the improved thermal barrier system improves the temperature capability of the system by providing a layer adjacent the substrate that has improved thermal performance and that is not subject to deterioration. The application of a silica layer of predetermined thickness adjacent the substrate also forms a diffusion barrier for oxygen while eliminating the need to transform an external layer of the substrate by a pre-oxidation step. This diffusion barrier prevents any oxidizable component of the substrate from decomposing. The thermal/environmental barrier coating (T/EBC) system includes an intermediate layer containing YSZ and BSAS, mullite and/or alumina, which is preferably used in combination with a mullite layer that overlies the surface of the silica layer, a layer of BSAS between the mullite layer and the intermediate layer, and a thermal barrier coating of YSZ overlying the intermediate layer.