Abstract
We discuss the results of the study of carbon steel 20 boriding performed by the micro-arc chemical-thermal treatment of a mixture containing iron and boric acid. The study has been carried out in scientific laboratories of the EKSU named after S. Amanzholov. It is found out that boride diffusion coatings obtained by this method are characterized by high hardness of 3.5 GPa and have an extensive diffusion zone. The wide diffusion zone is a surface layer of steel in which the compounds of boron and iron are distributed so that a transition region is formed between the hardened region and the matrix. The material of the diffusion zone is a composite consisting of a plastic а-phase of iron and high strength iron borides. X-ray diffraction studies revealed the formation of Fe3B compounds. It is found that the most optimal composition of the mixture contains iron and boric acid in a ratio of 1:3 (Fe-25% + H3BO3-75 %). The use of the micro-arc surfacing method makes it possible to intensify the process of diffusion boriding in comparison with traditional methods. Also, it ensures that a hardened composite layer with a heterogeneous structure formed by the diffusion-crystallization mechanism is developed on a surface of steel products.