Electocomposites with SiC content modulated in layers

Nickel electrochemical composites using different sublayers were deposited from a Watts bath containing, in addition, SiC particles of 1 and 5 mu m in dispersion. The layers differed both in the incorporated particle content and in their size, resulting from varying the regimes of bath stirring. A ductile underlayer with 0.7-1.1 vol.% of SiC was deposited from the non-agitated bath. Under non-intensive air agitation, an intermediate sublayer with 9.2-11.8 vol.% of the fine dispersed inclusions was obtained. When the most intensive agitation was maintained in the electrolyte, which also containing an additive of silanamine, the upper sublayer was plated with 12.6 vol.% of the dispersed phase. Compared with other layers, the latter contained a lot of the coarser particles and showed an enhanced hot-oxidation resistance. The hardness and internal stresses, the chemical corrosion rate, the morphology and surface profile of each sublayer were investigated. (C) 1998 Elsevier Science S.A.