Surface preparation for ceramics functionalization by thermal spraying

Dense sintered technical ceramics demand special surface preparation in order to be coated by thermal spraying. Sandblasting results in the damage of the interface region and leads to bonding defects. On the contrary, by varying the laser conditions, different laser structured surfaces were generated, which at Rz roughness values in the range of 40 mm, allowed to achieve thick and well bonding coatings. Therefore, laser ablation is proved to be the best method for surface preparation of ceramic substrates. In the case of porous ceramics (including pre-sintered ceramics) substrate preparation can be omitted, depending on their porosity level. Ceramics with porosity content up to 60 % can be coated by APS, whereas HVOF can be used on ceramics with porosity up to 30 %. On ready-to-get-coated pre-sintered ceramic parts (without substrate preparation), followed by co-firing of the substrates and coatings, the development of new ceramic components is possible.