A method of coating a metal substrate with a ternary or greater alloy of a predetermined composition is described. Initially, a 1st and 2nd metal are electrodeposited on the substrate using an aqueous electrolyte. Then, one or more metal powders (e.g., Cr) is simultaneously mixed in the electrolyte as the 1st and 2nd metals are electrodeposited so that a portion of the metal powder is occluded in the electrodeposited metal coating. The rate of occlusion of the metal powder is controlled by the vol % of the metal powder in the electrolyte. Finally, the metal coating and the substrate are heat treated to diffuse the occluded metal powder in the coating and to form the desired alloy coating. A plurality of metal powders can be mixed in the electrolyte according to the present method. In addition, a diffusion barrier coating can be initially provided on the metal substrate. The method is particularly useful with fe-based metals, such as stainless steels. The rate of occlusion of the metal powder is additionally controlled for fe-based metals using a fe-ni plating solution by controlling the presence of reduced fe2+ ions. The microstructure of the electrodeposited coating also affects the occlusion rate. The rate of occlusion was also increased by varying the current density.
U.S. Patent No. 4,601,795, July 22, 1986