The Metallurgy of Iron-Nickel and Iron-Nickel-Cobalt Diffusion Coatings

ISSN： 0008-4433

Source： Canadian Metallurgical Quarterly, Vol.25, Iss.4, 1986-10, pp. : 327-335

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Abstract

This paper describes the metallurgy of iron-nickel and iron-nickel-cobalt diffusion coatings produced by heat-treating nickel and nickel-cobalt alloy electrodeposits. These deposits were produced using a concentrated sulphamate plating solution. The cobalt content of the electrodeposits varied between zero and 53.6%; all the deposits were applied to an AISI 1022 steel, and the heat-treatment was carried out in a vacuum furnace for periods of between 8 and 50 h at temperatures between 900 and 1010°C.All the coatings thus produced were completely face centred cubic at the outer surface and had a martensitic zone situated close to the original electrodeposit–steel interface. The presence of cobalt in the electrode posit reduces the diffusion coatings' grain size and substitutionally alloy hardens the outer regions of the coatings. Both these factors increase the overall surface hardness.