№1 2024

Materials science

Creation of gradient structures in samples from vt6 alloy by induction hardening

A.V. Neiman, O.A. Bytsenko, M.D. Tevs, A.P. Neiman

The possibility of forming a gradient structural state in samples from the VT6 alloy using induction hardening followed by aging was investigated.

It is shown that as a result of such treatment a structure with a finely dispersed α-phase is formed in the surface layer, obtained as a result of the decomposition of the metastable β- and α'-phases. In the core of the samples, the type of structure of the original rod is retained with the additional release of a finely dispersed α-phase during the β→α-transformation. In this case, a hardness gradient is achieved from 34 units in the core to 39 units on the surface.

The possibility of varying the depth of the strengthened layer from 3 to 5 mm by changing the heating time of the samples and the electrical parameters of the inductor has been shown.

Keywords: induction hardening, hardness, titanium alloys, endoprostheses.

The influence of hydrogen alloying and thermal hydrogen treatment on the machinability of Ti-8,7Al-2Mo-1,5Zr alloy by cutting

A.A. Lidzhiev, A.M. Mamonov, A.V. Ovchinnikov, E.O. Agarkova, A.P. Neiman

The effect of hydrogen alloying and subsequent vacuum annealing of titanium alloy Ti-8.7Al-2Mo-1.5Zr on the cutting force and temperature in the cutting zone during milling was studied. The relationship between these parameters and the emerging phase composition and structure is shown. Differences have been established in the patterns of changes in temperature and cutting force depending on the structure in comparison with industrial titanium alloys.

Keywords: titanium alloy, hydrogen, structure, vacuum annealing, cutting force, temperature in the cutting zone.

Results of comparative corrosion tests of pipes made of PT-7M alloy with coarse grain and ultrafine grain structures

O.A. Bykh, A.M. Bakhmetev, P.V. Tryaev, A.V. Lukoyanov, A.N. Sozinov, R.A. Vlasov, A.S. Mikhaylov, E.E. Loginova

The paper presents the results of comparative tests for hot-salt corrosion resistance of pipes made of ПТ-7М alloy with coarse grain structure as per ТУ 5.961-11916-2007 and with ultrafine grain structure as per ТУ 24.45.30 202 07516250-2018. Regarding the depth of corrosion damage, no significant differences between the pipe specimens with different structures were found. Corrosion of pipe metal with coarse grain structure is characterized by pitting damage of intergranular nature whereas there is no such damage on the pipes with ultrafine grain structure. The hydrogen concentration in pipe specimens increases along with the increase of exposure to the testing medium, but even after 500 hours of testing its content in the metal under the areas of corrosion damage is not critical and does not reach the values which can lead to hydrogen embrittlement.

Keywords: titanium alloy, hot-salt corrosion, coarse grain structure, ultrafine grain structure, corrosion damage, hydrogen content, pitting corrosion

The effect of anisotropy and neutron flux irradiation on the operational reliability of zirconium iodide

S.V. Serikov

Using the example of metals important for the nuclear industry – zirconium, hafnium, the efficiency of the computational and experimental method for evaluating the operational reliability of the materials in question, already known from publications, is shown. From experiments on the effect of anisotropy, as well as neutron irradiation on the mechanical properties of zirconium iodide, a significant change in the level of crack resistance of the metal follows. Data on changes in the coefficient of dynamic viscosity of zirconium iodide and hafnium from the test temperature are presented.

Keywords: dynamic viscosity coefficient, specific work of destruction, genome-forming matrix, zirconium iodide, hafnium, deformation rate, temperature.

Manufacturing technologies

Development and implementation of technology for manufacturing powders and parts from titanium alloys using additive technology

M.N. Saubanov, A.A. Smagin

The analysis of the production of titanium powders for additive technology was carried out. A technology for production of initial cast titanium blanks from production waste to produce powders for additive and granulation technologywas developed and implemented. Titanium powder was producedfrom titanium alloys for shipbuilding and the aviation industry. The researches of microstructural analysis, chemical composition and gas content analysiswere carried out. Various parts were made of titanium powders by 3D printing method. Sintering modes were perfected. Mechanical testswere carried out.

Keywords: metal powder compositions, titanium sponge, granulation technology, gas atomization, centrifugal plasma spraying, SLM method, DED method.

Processing technologies

The increase of efficiency of titanium powder metallurgy by hydrogen alloying

K.S. Senkevich

The paper analyzes the main factors of influence of reversible hydrogen alloying on sintering of titanium and its alloys. Examples of promising technologies for obtaining compact and porous titanium semi-finished products are given using different approaches to the hydrogen application – sintering in hydrogen, sintering of titanium hydride, sintering under conditions of polymorphic and eutectoid transformations, thermocycling.

Keywords: powder metallurgy titanium, sintering, phase transformation.

Improving the quality of «П»-shaped forgings made of OT4-1 alloy without changing the tooling used

P.A. Golovkin

It is known that low thermal conductivity and high thermal conductivity of titanium and its alloys make it difficult to produce quality forgings and stampings with the specified types of microstructure and grain sizes. Due to the development of localised intergranular deformations in the forging material, a material structure is often formed that does not provide the required level of its crack resistance. By means of comparison of mathematical modelling and metallographic analysis of the material of «П»-shaped (in form of the Russian alphabetic character «П») forgings from Ti-Al-Mn alloy OT4-1 the possibilities of their quality improvement at minimum costs are investigated. It is shown that the control of deformation temperature and forming scheme are effective and simple ways to improve the quality of the material of the received stamped forgings while maintaining unchanged die tooling and equipment. Reducing the temperature of billets heating before stamping and their preliminary flattening in order to approximate the dimensions in plan to the future stamped forgings, reduce the localisation of deformation processes and the strain heating of the metal material caused by it. Increasing the uniformity of deformation processes, due to the limitation of intergranular deformation and predominance of intragranular deformation, allows to obtain «П»-shaped forgings with the specified types of microstructure of their material.

Keywords: titanium alloy, temperature, deformation, forging material, crack resistance, structure types, grain sizes, forging, stamping.

Manufacture in cmp jsc rods for medical appointment diameter from 5 to 16 mm, made of alloy Ti-6Al-4V ELI

D.N. Kharkovsky, A.S. Kropachev, R.B. Minibaev, I.N. Bazhenov, K.A. Bazhenov

Despite the sufficient intelligence of industrial ways of manufacturing rods from titanium alloys for medical consumption, in the free access there are almost no presented publications, illuminating the technological details and features of the manufacture of these products and their influence on the structure and mechanical properties.

This article describes method of manufacturing rods from ingots of titanium alloy Ti-6Al-4V Eli of domestic production, tried on industrial equipment in CMP JSC, appropriated the requirements of medical standards ASTM F136 and ISO 5832:3.

The stage of final actions, where the main consumer properties are emerged, is described in more details. There were tested several variants of drawing and calibration of rods, with using different industrial equipment and instrument.

During the working studied the relationships between oxygen content and mechanical properties of rods. Represented the results of research of structure and mechanical properties of manufactured rods according to requirements of ASTM F136 and ISO 5832:3.

Keywords: titanium alloys for medical purposes, high-precision processing of rods, straightness, mechanical properties, structure, oxygen content.

Computer simulation of isothermal stamping of medical products blanks made of high-modulus titanium alloy doped with hydrogen

A.M. Mamonov, A.A. Lidzhiev, E.V. Preobrazhenskii O.A. Polyakov, E.O. Agarkova

The isothermal stamping possibility of rasp blanks made of high-modulus hydrogen-alloyed titanium alloy using computer simulation has been studied. The processes of isothermal stamping of VT6 alloy hip joint endoprosthesis blanks and rasp blanks made of Ti-8.7Al-1.5Zr-2Mo alloy with 0.6 wt % hydrogen added were simulated. It is shown that when the workpieces heating temperature is 850 °C and their shapes and sizes are identical, the temperature, deformation and force parameters of the processes are very close in value and nature of distribution in workpieces volume.

Keywords: titanium alloy, hydrogen, computer simulation, stamping, rasp.

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