Development of HVOF-sprayed Ceramic Coatings

In this study three different, spray dried and sintered, spherical, ceramic powders were thermal sprayed using a kerosene HVOF-system. As feedstock materials pure Al₂O_3, a mixture of Al₂O₃ and TiO₂ (Al₂O₃-13TiO₂), and pure TiO₂ were utilized. The process parameters kerosene flow, oxygen flow and stand-off distance were varied with regard to the deposition efficiency, the coating porosity and microhardness. It was found, that the ceramic powders are appropriate as feedstock for HVOF-spraying. The different melting points of the used materials lead to differences, especially of the deposition rate. The mechanical properties of the three coating systems were compared and tendencies were illustrated.