This paper proposes the technology for obtaining antifriction coatings by short-pulse laser treatment of powder compositions. (Research purpose) The research purpose is in synthesizing thin anti-friction coatings on the surface of steel substrates by short-pulse laser treatment of metal powder compositions and analyze their physical and mechanical properties. (Materials and methods) A solid-state pulsed laser generator was used to synthesize antifriction coatings. B83 babbit powder has been used as an additive material. The powder composition was additionally doped with PMS-1 copper and molybdenum disulfide in order to increase the friction properties and load-bearing capacity of the coatings. Laboratory samples were subjected to wear tests under boundary friction conditions using the SMT-2070 friction machine in comparison with standard surfaces of B83 babbite coating, steel surface, and Molykote d-321R clad surface. X-ray diffractometer DRON-6 was used for x-ray diffractometry. (Results and discussion) It was found that the porosity of the modified coating does not exceed 5 percent, and there are no traces of detachment and destruction in the experimental samples. It was found that the coefficient of friction of the analyzed coating under conditions of boundary friction was 0.12-0.13, which corresponds to the coefficient of friction of a standard babbit alloy. The modified coating have a more efficient workability and a stable coefficient of friction over a large range of loads. It was found that the wear intensity of the analyzed coating is significantly lower than one of the compared surfaces. The increase in friction characteristics is due to the features of the coating structure, which is characterized by a large number of solid intermetallic compounds Cu3Sn having a hexagonal structure, which determines the low friction coefficient. (Conclusions) The results shows the high practical potential of modified antifriction coatings that can be used in mechanical engineering and repair production in the design and restoration of bearing assemblies.
The use of standard alloys, in particular steels, to increase the wear resistance of contact surfaces in mechanical engineering in most cases has lost its relevance due to low mechanical and tribological properties. Currently, in mechanical engineering, as well as in repair production, technologies for obtaining functional and restorative coatings that differ significantly from the properties of the product material are widely implemented. (Research purpose) The research purpose is in studying the physical and tribological properties of ceramic coatings obtained by laser melting of fine powder materials. (Materials and methods) Authors used a powder mixture based on boron carbide and nitride as the initial powder materials as the most solid, heat-resistant and chemically inert compounds, additionally doped with magnesium oxide and lithium. Authors used an ytterbium fiber laser with a maximum power of 50 watts as a laser radiation generator. (Results and discussion) It was found that laboratory studies confirm the high adhesion of the ceramic coating with a steel substrate. It also was found that stable chemical compounds based on iron carbides and borides are formed in the fusion zone. The article notes that the high impact strength of the coating was confirmed by the shock tests of samples-in the impact (destruction) zone, there is no formation of significant cracks and chips of the coating, the fusion zone without traces of separation and destruction. The article shows that the lowest coefficient of friction at elevated temperature and dynamic loads is observed in coatings with the presence of metal oxides, this is explained by the accelerated formation of a tribofilm based on boric acid. (Conclusions) The presented results have a high scientific basis and practical potential. The low coefficient of friction and high wear resistance allow to use the results of research in tribo-couplings that are operated under high temperatures and kinematic characteristics.
In the paper, the technology of obtaining antifriction coatings by the method of finishing antifriction-free abrasive treatment with the implementation of the wear-free effect is proposed. (Research purpose) The research purpose is in developing an effective technology for obtaining copper coatings on the surface of steel parts of the shaft type to reduce the wear rate in the conditions of oil starvation of machine parts. (Materials and methods) During the study, a laboratory facility for the synthesis of antifriction coatings on the surface of steel parts by the method of finishing antifriction-free abrasive treatment has been developed. Brass of the LS-59-1 brand was used as a material for applying a copper antifriction coating. In order to activate the surface of the part and the surface of the filler material, a technological medium based on a ten percent solution of hydrochloric acid and glycerol was used. Authors determined the composition of the technological environment empirically. The obtained laboratory samples were subjected to tribological studies in comparison with standard antifriction alloys. X-ray diffraction studies were performed to determine the phase composition. (Results and discussion) As a result of X-ray diffraction studies of laboratory samples, the presence of iron and copper components in the synthesized coating was studied. The content of oxides on the surface of the coating is insignificant, the internal structure is dense with no visible porosity. The coating consists of 95 percent copper, the synthesis process takes place without oxidation, which gives the coating a high adhesive and cohesive strength. The coating thickness is uniform and varies within 3-5 micrometers. (Conclusions) Comparative tribological studies have shown high resistance to wear and to the setting of the contact surfaces under conditions of oil starvation. The coefficient of friction is stable and low and is in the range of 0.08-0.15. The developed technology makes it possible to increase the wear resistance of steel parts of the shaft type in the shortest possible time and with minimal material costs and can be successfully implemented in the conditions of repair enterprises.
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