Effect of the Elemental Composition of Steels on the Structure and Properties of Ni–Cu Coatings Produced by Diffusion Alloying from Fusible Liquid-Metal Melts

The results are presented of diffusion alloying in the medium of low-melting liquid-metal solutions (DALLS) of St3, 40Kh, and 40Kh13 steels in a Pb–Li eutectic medium with the addition of Ni and Cu. Coatings 16–20 μm thick were formed as a result of DALLS. The maximum coating thickness was observed on St3 steel and amounted to 20 μm. On 40Kh steel, the coating thickness was 17 μm, and on 40Kh13 steel it was 16 μm. Structurally, the coatings consisted of surface and transition layers. The content of alloying elements in the coatings also depended on the substrate material. On 40Kh13 steel, the maximum nickel concentration was 46% and the copper concentration was 13%. On 40Kh steel, the maximum nickel concentration was 44% and the copper concentration was 11%. On St3 steel, the maximum nickel concentration was 40% and the copper concentration was 9%. In all cases, the nickel diffusion depth exceeded the copper diffusion depth. The microhardness of the coatings at a depth of 5 μm was 125 HV0.02 for St3, 130 HV0.02 for 40Kh, and 140 HV0.02 for 40Kh13 steel.