OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 2 2023 Fig. 9. Distribution of boron over the layer depth on steels after plasma-jet hard-facing the dilution of the smearing mixture with the base material. As a result, the concentration of boron in the hard-faced layer decreased, and vice versa, the proportion of the eutectic component increased. The lowest value of the hardness of the alloyed layer is 452 HV (obtained at a current of 160 A), because the surface layer after boronizing has a hypoeutectic structure and the lowest boron content. It is interesting to note that the slight hardness gradient observed over the depth of the coating, as well as the gradual decrease in hardness due to the presence of the transition zone, are considered favorable for good adhesion of the boride layer to the surface of the base material. For example, the sharp jump in hardness between the boride layers and the base metal observed in diffusion boronized layers is considered to be one of the main causes of poor adhesion leading to peeling and splitting of coatings. Conclusions 1. In the course of the conducted studies, it is found that it is possible to obtain boride layers on the surface of steel using the technology of plasma-jet hard-facing of a boron-containing coating. Fig. 10. Distribution of microhardness over the depth of hardened layers
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