Functionalisation of ceramic surfaces with thermalspray coatings

The aim of the present work was to develop thermal spray coating solutions for flexible, targeted modification of the functionality of ceramic substrate surfaces. In principle, all ceramic substrates of sufficient strength can be coated. Substrate preparation can be omitted for porous ceramics (including presintered ceramics), with the porosity limits differing for the different spray processes (approximately 60% porosity for APS and approximately 30% for HVOF and S-HVOF coatings). Dense technical ceramics require substrate preparation. However, because sandblasting results in damage to the substrate and bonding defects, laser ablation is the best method for substrate preparation. Thick coatings with good substrate bonding can be achieved if the Rz roughness values are about 40 μm. Manufacturing ceramic substrates with coatability in mind allows the substrate preparation step to be eliminated, thus providing completely new technological options such as coating of presintered ceramic parts followed by cofiring of the substrates and coatings.