PRODUCTION AND MECHANICAL-PROPERTIES OF POWDERS COATED BY ELECTROLYSIS AND OTHER PROCESSES

Iron powders have been coated with a number of metallic coatings containing copper, nickel, and lead. An atomised iron powder was used as the substrate on which these metallic coatings were deposited using three 'wet' techniques, namely: (i) electrolysis; (ii) electroless (or chemical) methods; and (iii) chemical displacement methods. A liquid based fluidised bed reactor was used, which enabled multilayered deposits to be laid down on the iron particles. The results show that it is possible to produce composite coatings such as Cu-Sn, Cu-Pb, for example, and coherent coatings are formed, giving an even thickness around each particle. The powders take up the properties of the coating once a critical thickness has been reached and this coating controls the mechanical behaviour of the powders. Copper coatings produced on iron particles by chemical displacement gave greater green strength to the compacts than coatings of copper produced by the other methods.