Morphological development of electrodeposited Ni-Al particle composite coatings

Electrodeposited metal matrix/metal particle composite coatings (EMMC's) were deposited and characterized. Nickel matrix/aluminum particle coatings deposited on a nickel substrate was chosen as a model system. The microstructure of the as-plated coatings was characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and quantitative image analysis (QIA). A schematic model is presented for coating morphological development during codeposition of small, electrically conducting particles. By varying the processing parameters, coatings with up to approximately 20 vol.% Al particles were obtained. At high deposition current densities, the Ni-Al EMMC coatings exhibited a higher microhardness than pure Ni coatings deposited under similar conditions. This effect is due to a microstructural refinement of the coatings caused by the Al particle additions.