Low thermal conductivity coating system for application up to 1000°C by simple PDC processing with active and passive fillers

In this work, the development of a novel thermal barrier coating system based on polymer-derived ceramics, applied by simple lacquer methods is reported. The system consists of a polysilazane (PHPS) bond-coat and an insulating layer formed by the combination of passive (YSZ) and active (ZrSi2) fillers with a (organo)silazane (Durazane 1800). The aim of this study is to investigate the influence of type and amount of the different fillers on the coating formation and properties, as well as to obtain high thickness, strong adhesion and low thermal conductivity. The resulting coatings and their components were investigated by TGA, XRD, SEM, and EDX. The adhesion was analyzed by cross-cut tape test and by pull-off test. The thermal conductivity was measured by 3ω-method. The best coating system presents thermal stability up to 1000 °C, thickness of 50 μm, pull-off adhesion of 10 MPa and outstanding low thermal conductivity of 0.44 W (m K)−1.