3. Objects of study are the processes of surface nanostructuring and change the energy state of the surface under the influence of various factors. The aim of the thesis is to develop the most effective and least expensive way to improve the structural strength of steel machine parts based on the research and analysis of the effect of different methods of surface effects, including surface nanostructure on the properties of not only surface but also the whole product as a whole. Research methods and equipment. We used X-ray (SEM-106) and X-ray analysis (DRON-3), optical (MIM-7) and E (REM-106) microscopy, determination of mechanical characteristics in static (tensile - P5) and cyclic (fatigue - MIE-6000) trial, a study of the surface profile and roughness parameters (TR-200), the measurement of macro-and micro-and nanohardness (TP-7R-1, PMT-3, Nano Indenter II, respectively). The experimental results are processed by methods of mathematical statistics in the program Microsoft Office Excel. Theoretical and practical results. A theoretical justification of obtaining a high structural strength of products in surface nanostructuring. It is shown that ion bombardment (IB) with low-energy ions under certain conditions leads to healing of surface defects and the formation on the surface of products nanocrystalline layer with a thickness of about 30-50 nm. In such a layer of plastic deformation occurs notdislocation mechanism of grain boundary sliding nanograins. This prevents the formation of stress concentrators and grinding of metal, resulting in an increase in strength in the bulk of the material without sacrificing ductility. Novelty: 1. The first time the systematic study and analysis of various methods of surface treatment (ХТО, mechanical and electrolytic polishing, ППД, ІПО) on the bulk mechanical properties of the product. Experimentally proved that all analyzed activities alter the fine structure and three-dimensional characteristics of strength and ductility. The role of each factor in increasing the structural strength. It is shown that does not show the strong link between macrostresses ?I, exponents of the fine structure (?, the size of the ОКР, ?II) and mechanical properties. 2. For the first time directly on the real products revealed that the IB leads to a unique combination of characteristics of strength and plasticity, which has still not been achieved by any known combination of ways of strengthening. After IB temporary resistance for the samples without stress concentrators increased by 17 %, yield 34 %, while maintaining and even some increase in ductility (relative narrowing increases by 3 %). For products with stress concentrators, this effect is even more: ?v increased by ~ 69 %, ?0,2 ~ 84 %. Subsequent coating increases strength index no more than 3-7 %. 3. It was shown that low-energy IB ions (1 keV) under certain conditions leads to the formation on the surface of products nanocrystalline layer with a thickness of about 30-50 nm. The hardness of this layer compared with the baseline (before IB) on the surface (<20 nm) increases from 7.8 to 12.4 GPa, but decreases sharply and at a depth of 30-50 nm is virtually identical to the original in the work-hardened layer. After coating hardness increased almost threefold (to 21 GPa) and decreases much more slowly, so the depth of the hardened layer is much larger. Comparison of changes in hardness and the depth of the hardened layer with the mechanical characteristics of the product shows that a significant increase in their just after the IB can not be explained by the increase in hardness, as a rule of additivity is not satisfied. 4. First proposed a hypothesis to explain the receipt of a high structural strength of products in surface nanostructuring. In the process of IB by the healing of surface defects and the formation of the nanocrystalline layer. In such a layer of plastic deformation occurs notdislocation mechanism of grain boundary sliding nanograins. This prevents the formation of stress concentrators and embrittlement of the metal, resulting in increased strength in the bulk of the material without sacrificing ductility. The degree of implementation. On the basis of the results of theoretical and experimental research was developed to improve the structural strength of products (patent of Ukraine № 55911 "Method of increasing structural strength of steel products). The developed method is especially effective if the product has concentrators. So if, for smooth specimens increase tensile strength and proof stress after IB was 17 and 34 % respectively, then the bolt thread - 69 and 84 %. Sphere (region) use. Research results that are presented in the thesis can be used for machine-building enterprises for parts requiring high structural strength and operating at large tensile stresses, as well as academics and students of technical universities.
