Previous experiments have shown – in accordance with thermodynamic calculations – that corundum is resistant to oxidizing high-temperature chlorine corrosion conditions. Although it offers outstanding corrosion resistance, its mechanical properties – in particular its brittleness and low thermal shock resistance – make it inapplicable as a material for large moving components such as rotary furnace tubes.
A new coating concept combines the chemical resistance of corundum with the mechanical properties of an alloy. It consists of a two-layer thermal spray coating system with a ceramic top coat and a corrosion resistant metallic NiAlMo bond coat that is specially designed for the use in reducing environments that can be expected under the ceramic top coat. Results from the coating development and their performance under the testing conditions will be reported in the paper.