OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 2 2023 Structure and properties of low carbon steel after plasma-jet hard-facing of boron-containing coating Andrey Balanovsky a, Van Vinh Nguyen 2, b, *, Natalia Astafieva c, Ruslan Gusev d Irkutsk National Research Technical University, 83 Lermontova st., Irkutsk, 664074, Russian Federation a https://orcid.org/0000-0002-6466-6587, fuco.64@mail.ru, b https://orcid.org/0000-0001-6514-9015, nguyenvanvinh190596@gmail.com с https://orcid.org/0000-0003-4957-9597, anstella@mail.ru, d https://orcid.org/0000-0003-4217-1329, deltadota_99@mail.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2023 vol. 25 no. 2 pp. 93–103 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2023-25.2-93-103 ART I CLE I NFO Article history: Received: 02 March 2023 Revised: 24 March 2023 Accepted: 12 April 2023 Available online: 15 June 2023 Keywords: Plasma cladding Amorphous boron Iron borides Coating Acknowledgements Research were partially conducted at core facility “Structure, mechanical and physical properties of materials”. ABSTRACT Introduction. One of the effective thermochemical methods for increasing the hardness of steel is boronizing by diffusion of boron atoms into the steel surface at high temperatures. As a result of boronizing, coatings are formed on the steel surface, consisting of columnar crystals of FeB and Fe2B. The volume fraction of phases and the thickness of the coatings depend on the heating temperature and the chemical composition of the base material and the saturating medium. The main disadvantage of these boronized layers is its high brittleness. Boronizing by plasma heating is one of the alternatives to the diffusion boronizing process to minimize the brittleness of the boronized layer. The purpose of the work: to form boride coatings on low-carbon steel using plasma-jet hard-facing. The research methods are: determination of the content of chemical elements using an electron probe micro-analyzer, metallographic studies, analysis of the phase composition of the boronized layer, as well as measurement of the microhardness of the coating after plasma-jet hard-facing. In this work boronized layers obtained on low-carbon steel 20 by plasma-jet hard-facing of a boron-containing coating are studied. Powdered amorphous boron was used as an alloying element. The parameter varied during plasma-jet hard-facing process is the current strength (120 A, 140 A and 160 A). Results and discussions. Based on the studies performed, it is found that it is possible to form boronized layers on the steel surface using plasma-jet hard-facing method. It is noted that the surface layer of the coating of the 1st and 2nd specimens after plasma-jet hard-facing has a heterogeneous structure, consisting of rows of different zones. The first zone has a hypereutectic structure, which consists of primary borides FeB and Fe2B, located in the eutectic, consisting of Fe2B and α-Fe. The second zone above the boundary with the base metal is represented by eutectic colonies composed of Fe2B and α-Fe. The third specimen is characterized by a hypoeutectic structure consisting of boride eutectic and primary dendrites of the α-solid solution of boron in iron. The maximum hardness is fixed on the surface of the first specimen and is 1,575 HV. The depth of the hardened layer increases with increasing current, but the hardness value and boron content decrease after treatment. 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 boronized layer to the surface of the base material. For citation: Balanovsky A.E., Nguyen V.V., Astafieva N.A., Gusev R.Yu. Structure and properties of low carbon steel after plasma-jet hardfacing of boron-containing coating. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2023, vol. 25, no. 2, pp. 93–103. DOI: 10.17212/1994-6309-2023-25.2-93-103. (In Russian). ______ * Corresponding author Nguyen Van Vinh, Post-graduate Student Irkutsk National Research Technical University, 83 Lermontova st., 664074, Irkutsk, Russian Federation Tel.: 89050160252, e-mail: nguyenvanvinh190596@gmail.com Introduction It is known that during the operation of steel parts and tools, the surface layers are subjected to the most intense external influences, therefore, the structure and properties of the surface layers often have a decisive influence on the performance of products as a whole. Therefore, the formation of surface layers with the necessary functional properties is more profitable than the production of steel with similar properties, and in some cases it is the only technically possible solution [1–3].
RkJQdWJsaXNoZXIy MTk0ODM1