Reaction Diffusion between Carbon Steels and Molten Lead Saturated with Chromium

Abstract

Various kinds of carbon steel specimens containing 0.15-0.8 mass%C were annealed in the molten lead saturated with chromium at 1173 to 1373 K. The formation and growth kinetics of the chromium carbide layer by the reaction diffusion between the specimen and the Pb-Cr melt has been investigated. Four kinds of carbide layers composed of the following structures were formed on the specimen surfaces depending on annealing temperature and the carbon content of the specimen: S/Cr₇C₃, S/Cr₂₃C₆, S/Cr₂₃C₆/Cr₇C₃/Cr₂₃C₆ and S/Cr₇C₃/Cr₂₃C₆, where the letter “S” means the steel substrate. These carbide layers contain a large amounts of iron, grow according to the parabolic law and have Vickers hardness of 1700-2000. The method used in this work is applicable to the chromium carbide coating on carbon steels containing more than 0.15 mass%C.