Nickel–alumina graded coatings obtained by dipping and EPD on nickel substrates

Nickel substrates have been coated by Ni/Al2O3 composite films by a dipping process using aqueous suspensions that contain a temporary binder. Two-layer and three-layer graded coatings have been produced, consisting of pure Ni powder and Ni/Al2O3 composites with Al2O3 contents of 15 and 30 vol.% as intermediate layers to release sintering and thermal stresses. The laminates were further coated with a ceramic layer of Al2O3/ZrO2 that was deposited by electrophoretic deposition using a non-aqueous suspension. A continuous, thin Al2O3 layer surrounding Ni grains developed at the intermediate composite layer of Ni/Al2O3 allows the ceramic coating to maintain strongly adhered to the nickel substrate by means of a porous substrate/coating interface.