High Temperature Corrosion and Erosion Properties of Thermally Sprayed Ceramic Oxide Coatings

Oxides are chemically stable and wear resistant materials. Because of these properties, they are often applied as protective coatings in harsh environments. However, their chemical and mechanical stability at high temperature in chlorine containing environments is uncharted. These conditions are present in waste-to-energy and biomass boilers in which the currently available metallic and metal matrix composite coatings provide unsatisfactory protection. To be effective in these conditions the coatings should be chemically inert, erosion resistant and act as environmental barriers. For this purpose, this research studies the corrosion and erosion behaviours and microstructural features of HVOF- and APS-sprayed Al₂O₃-, Cr₂O₃-, TiO₂-based coatings. Their chemical stability was evaluated by high temperature corrosion testing of self-standing coatings under KCl salt deposit at 550, 650 and 720 °C for the duration of 72 hours. In addition, the coatings were tested in erosion under high temperature conditions with corundum abrasive particles.