Influence of Diffusion Alloying of Steel 20 in Medium of Low-Melting Liquid Metal Solutions by Elements of Ni–Cu System on Elemental Composition and Properties of Surface Layers

Abstract—The influence of diffusion saturation of steel 20 in the medium of low-melting liquid metal melts of Pb–Bi–Li–Ni–Cu composition on its elemental composition and corrosion resistance is considered in this article. As a result of diffusion saturation, a coating is formed structurally consisting of two zones: surface and transition ones. The surface zone contains 53% Cu, 30% Ni, and 17% Fe. As one approaches the transition zone, a decrease in the concentration of Cu and an increase in the concentration of Ni and Fe are observed. In this case, the transition zone structurally consists of inclusions of Fe in a Ni-based solid solution that did not pass into solid solution. In addition, there is a layer under the coating containing C in a higher concentration than the base material owing to the low solubility of C in solid solutions of the Cu–Ni–Fe system. The coating thickness ranges from 8 to 45 μm depending on the temperature and duration of saturation. It is also found that the resulting coatings can reduce the corrosion rate of samples from 3 to 0.8 mm/year.