currently, the development of biomaterials that have the required characteristics for various tissues is one of the main problems in medicine and engineering. Obtaining calciumphosphate coatings on metal surfaces is one of the urgent problems in materials science. Nevertheless, there is no unambiguous data on what physicochemical properties (phase and elemental composition, structure, crystallinity, roughness, solubility, etc.) should have an implant surface that ensures its osseointegration. In this work, to obtain calcium-phosphate coatings, we used the method of detonation-gas spraying of powder materials on a Grade2 titanium base. A TiAl 3 mixture with the addition of calcium hydroxyapatite was used as powder materials. The mass percentage of TiAl 3 in the mixture was 40%, 55%, 65%, 80%. The topography of the coating surface was determined by computer three-dimensional modeling based on data obtained using a Zygo New View 7300 interferometer-profilometer. It was found that with an increase in the intermetallic content in the TiAl 3 mechanocomposite with hydroxyapatite ( Ca 10 (PO 4 ) 6 (OH) 2 ), the layer roughness of the surfacing of composite materials increases from Ra = 2.628 µm to Ra = 3.490 µm . At the same time, the roughness of the layer has an important role in the growth of bone tissue. Comparative analysis of the dependence of bone tissue growth on the roughness of coatings showed that layers obtained by detonation-gas spraying based on hydroxyapatite have a higher efficiency of about 100% of bone tissue growth at roughness values Ra = 2-4 µm .
The article researched the influence on the pipes mechanical properties initial billet obtained by the traditional method and the proposed method, in which the piercing process is excluded. The proposed method involves casting the initial billet for the production of seamless pipes with a cavity obtained on a continuous casting machine. The production of hot-rolled seamless pipes from a hollow billet is an urgent issue today, since central porosity and axial segregation after casting are excluded, affecting the quality of the pipes obtained in the subsequent stages of production: rolling on a mandrel mill and reducing. The result is a minimal deviation of the mechanical properties of steel samples obtained by double deformation of a hollow continuously cast billet from samples obtained according to the traditional scheme, including the piercing process.
This article describes the developed methodology for the prompt and reliable determination the mechanical properties quantitative indicators of the heat-treated steel products by a non-destructive method. For these cases, the non-destructive method of testing steel products is the most optimal option, due to the fact that it does not require destruction of the controlled sample and provides for the possibility of the product further operation. The use of non-destructive testing methods also contributes to significant savings in material and time resources. The essence of the method described in this work lies in the initial study of steel samples, measuring their coercive force, maximum magnetic permeability and residual magnetic induction for subsequent statistical analysis to determine the relationship between mechanical and electromagnetic properties. As a result of finding this correlation and checking its reliability, it becomes possible to determine the ultimate strength, yield strength and relative elongation on finished products, which are normalized indicators of the steel structural products strength properties. The proposed non-destructive method for determining the mechanical properties will allow its use in the production flow, while having the reliability of determining the quality indicators above 96 %.
This paper presents the research results of solid structure and hollow steel billets obtained by continuous casting. To substantiate the feasibility of using a hollow billet as an initial one in the production of seamless hot-rolled pipes, a comparative analysis of the distribution of non-metallic inclusions, macro- and microstructure, as well as segregation by structural zones was carried out. When analyzing the macrostructure of a hollow billet, two distinct zones were revealed: equiaxed small and columnar crystals, which distinguishes it, compared with a solid billet, by the absence of a zone of misoriented crystals. This, in turn, helps to eliminate defects such as axial porosity and segregation. The improved quality of the macrostructure during casting of a hollow billet is explained by more favourable conditions for heat removal and a higher rate of solid-phase advance due to bilateral cooling, and less shrinkage of the melt due to its cross-sectional geometry. The distribution of nonmetallic inclusions, consisting of oxide, sulfide and oxysulfide compounds, and liquidation elements, showed that they are concentrated mainly at the boundaries of crystalline zones, and for a solid billet and in the central part. This fact is caused by the development of a zone of intense heat removal. When research the microstructures of solid and hollow workpieces, a ferrite-pearlite mixture is observed in both cases. The microstructure of the hollow billet is more dispersed, which is confirmed by durometric measurements.
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