Electrophoretic deposition applied to thick metal–ceramic coatings

Electrophoretic deposition was used to fabricate thick (⩾4 mm) metal–ceramic deposits from a non-aqueous slurry of nickel and alumina particles. A high solid volume in the slurry was identified as the primary parameter for depositing thick cermet coatings rather than the applied electric potential or ionic additive concentration. Ionic additives (MgCl2, AlCl3, etc.) were found to adequately suspend the alumina particles and provide rapid deposition rates. The nickel particles proved to be more difficult to suspend in solution, thereby sacrificing control of the deposition composition. The use of small (3.0 μm) particles and continuously pumping the slurry alleviated the suspension problems but small electric potentials (⩽100 V/cm) were required to avoid the formation of rough, columnar deposits on the depositing electrode.