International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The work aimed to evaluate the effect of microalloying titanium in proportions of 1 to 5 wt.% on the microstructure and microhardness of a precipitation-hardenable martensitic stainless steel. The standard chemical composition of martensitic steel 17-4PH was used, to which 1; 2; 3; 4 and 5 wt.% Ti was added, respectively. Microstructural analyses revealed changes in the crystal grains and precipitation effects from the solid solution of the alloy. Microhardness measurements were also performed, which demonstrated that withincreasing Ti content in the alloy the metallic matrix becomes harder. The study confirms that microalloying with Ti is beneficial for the development of martensitic stainless steels to increase mechanical properties, even without the application of subsequent heat treatments.
The results obtained in this work represent a starting point for the development of new customized alloy recipes, adapted to specific applications, where a high value of hardness, as well as microstructural stability or wear resistance are required.

A novel two-stage approach for obtaining wear-resistant multifunctional powder composites based on metal powders with highmodulus Ti–TiC system fillers is proposed. The method combines high-voltage electric discharge (HVED) treatment and spark plasma sintering (SPS), offering a promising alternative to conventional techniques for producing Al–Ti–C system composites. This approach enables the development of a unified route for material synthesis using high-energy-density processing. HVED treatment prevents oxidation of metal particles, reduces contamination by tool materials, and initiates the synthesis of additional dispersed strengthening phases. For example, HVED treatment of titanium powder in a hydrocarbon liquid promotes the in situ formation of titanium carbide (TiC) particles.
The present work investigates the influence of adding Ti–TiC powder—synthesized via HVED in ethanol under reverse polarity mode with a specific energy input of 20 MJ/kg—on the structure, phase composition, and properties of Al–Ti–C metal matrix composites (MMCs). It was shown that the addition of 2 wt% of Ti–TiC powder synthesized via HVED in ethanol to aluminum powder results in an MMC with an electrical resistivity of 0.5 Ω·mm²/m and a hardness of 31 HRB. However, the heat resistance of this composite is 2.5 times lower than that of consolidated pure aluminum powder. Increasing the Ti–TiC content to 10 wt% leads to the formation of a wear-resistant Al–Ti–C composite, whose structure includes Al, Ti, TiC, the intermetallic compound Al₃ Ti, MAX phases Ti₂ AlC and Ti₃ AlC₂ , and free carbon. For the MMC sample with the addition of 10% Ti–TiC, the mass gain per cycle during the heat resistance test is 0.23%/cycle, whereas for samples made from consolidated Al powder it is 0.18%/cycle, indicating that their heat resistance is approximately the same. The wear resistance of this composite is more than three times higher than that of the consolidated base aluminum powder, with wear rates of 0.003 g/km and 0.010 g/km, respectively. This material also demonstrates a hardness of 43 HRB and relatively low electrical resistivity at the level of 0.3 Ω·mm²/m.

The effect of individual additions of Ti and B into high chromium white cast irons (HCWCIs) on the structure, corrosion and selected mechanical properties was investigated. Two different heat treatments were applied, high-temperature treatment at 960 oC/1h, and subcritical treatment at 550 oC/4 h. The microstructure was investigated by OM and SEM; compositions of matrix and carbides were analyzed by EDS. Mechanical behavior of HCWCIs was analyzed by measuring hardness, toughness, abrasive/wear resistance and resistance to repeated impacts. Corrosion behavior was evaluated electrochemically, by linear and Tafel polarization methods in 0,1M NaCl solution. The properties of the modified HCWCIs were compared with the properties of the base unmodified HCWCI alloy (ASTM A532-IIE).

High-voltage electrical discharge (HVED) treatment of powder mixtures is a modern, efficient, and economically advantageous method for both particle size reduction and modification of the material’s phase composition. The primary mechanisms of particle destruction within the discharge zone include shock waves, microcavitation, ablation, collisions with chamber components, and mutual abrasion between particles.
The application of machine learning methods to model HVED processes for titanium—a promising material for composite applications— enables more accurate predictions and optimization of the technological workflow.
The data used for modeling were obtained between 2013 and 2021 and include results from the treatment of the initial titanium powder (with an average diameter of d₀ = 60 μm) in ethanol. This setup enabled the formation of a volume-distributed multi-spark discharge (VMD) within the ethanol–powder dispersed system. The dataset includes information on the number of treatment pulses, discharge gap, pressure in the discharge channels, pressure on the chamber walls, and the amount of titanium carbide formed during the treatment process.
It was shown that the concentration of TiC gradually rises with the increase of specific treatment energy, regardless of the interelectrode gap. Specifically, at a specific energy (Ws) of 5 to 15 MJ/kg, the amount of titanium carbide reaches 10%; at 15 to 30 MJ/kg, it increases to 20%; and at energy levels above 30 MJ/kg, the TiC content reaches 30%.
Keywords: Ethanol, Titanium, Titanium Carbide, High-Voltage Electrical Discharge, Volume-Distributed Multispark Discharge, Electric Discharge Dispersion, Plasma Technologies, Machine Learning, Logistic Regression, Random Forest

Tribological tests were carried out on four Ti-TiC composite samples to investigate the tribological behaviour of this alloy and the influence of sintering parameters on it. The samples were sintered by SPS using a high voltage electrical discharge. The general sintering parameters of the samples are temperature – 1100°C, heating rate – 10 °C/s, heating time – 3 min, initial pulse current – 260 A, maximum pulse current – 500 A. The different parameters are as follows: the number of pulses used for the first and fourth samples is 1000, for the second and third samples 2000; for the first and second samples a 1 electrode system was used, for the third and fourth samples a 3-electrode system. The hardness of the samples was measured using the Vickers method. The first specimen, sintered with 1000 pulses and 1 electrode system, has the highest hardness of 456.84 HV10. This is related to the fact that this sample showed the best tribological properties: the lowest friction coefficient of 0.39 and the lowest wear rate of 6.4∙10-4 mm3/Nm. It was observed that the samples sintered with 1000 pulses had lower average coefficients of friction: the average coefficients of friction of the first and fourth samples are 0.39 and 0.48 respectively, while the second and third samples are 0.54 and 0.51 respectively. The friction and wear characteristics of the first specimen, which has the best tribological properties, were compared with those of a Ti-Al-V alloy widely used in aviation. The Ti-TiC sample showed a better friction coefficient and better wear characteristics.

The protective coating on a cubic-shaped titanium sample was deposited by the plasma method in an argon atmosphere in several stages, in order to form a continuous barrier on all surfaces of the sample. It was shown that, when the protective coating was deposited by the specified method, partial or complete melting of the powders occurred, and subsequently, when they were deposited on the surface of the substrate, active interaction occurred. This made it possible to form a sufficiently continuous layer on the surface of titanium due to mutual diffusion. It is found out that the deposited protective coating allows titanium to be heated up to 400 ± 10 °C in a hydrogen atmosphere (hydrogen pressure 0.6 ± 0.2 MPa) without interaction with the gas.

This article describes the metal titanium, its characteristics and properties, and the types of titanium alloys with regard to its microstructure. It also describes the production processes, i.e. the melting and casting processes of titanium alloys. The focus is on the production of titanium alloys by the electric arc process, and possible hazards in the production of titanium in electric arc furnaces are also described. Suitable protective measures to be taken in the event of a particular hazard are also highlighted. Concerning the occurrence of possible accidents in the production of titanium, a calculation is also presented that shows how much needs to be invested in protection against possible accidents while maximising profit. Finally, the application and casting process of titanium alloys in dentistry is presented.

The possibility of using machine learning methods to predict the results of high-voltage electric discharge treatment of titanium powder in a hydrocarbon liquid is studied. As a result of the work, distribution surfaces for the average particle diameter of Titanium powder. the amount of Titanium carbide formed during processing, and the number of spherical particles of titanium powder depending on the interelectrode gap and the number of pulses, when using spark discharge and with Titanium powder concentration in kerosene of 0.07 kg / dm3, pulse repetition frequency 0.3 Hz and the energy of single discharge of 1 kJ, were obtained.

The results of the estimation for the influence of titanium diboride content in the initial powder mixture on the basic mechanical properties at the tests on tension and compression are presented. It is shown that the porosity of sintered at 1250 0C preforms from TiH2-TiB2 powder mixture increases with increasing of titanium diboride content in the initial charge, which is due to the manifestation of the Frenkel effect at sintering. The values of tensile strength, hardness and elastic modulus, despite some porosity growth of the sintered alloy, increase with the addition of 5 % of TiB2 powder, while increasing the content of the high modulus component in the mixture to 10 % leads to decrease in the level of these characteristics. The plasticity of sintered alloys monotonically decreases with increasing of the boride component content. At compression tests, the yield point and the compressive strength increase monotonically with increase in TiB2 content, despite the increase in porosity of the latter, due to a significantly lower effect of porosity on the value of the resistance to deformation in compression compared with tension. The use of hot forging of sintered powder preforms leads to increase of strength properties and hardness of the composites.

Peculiarities of titanium carbide obtainment by high voltage electric discharge synthesis (HVED) are considered in present paper. Mathematical and physical modelling of processes that occur during HVED impact on “Ti powder – hydrocarbon liquid” disperse system is performed. HVED creates thermodynamic conditions for pyrolysis of hydrocarbon liquid with formation of solid-phase carbon and gaseous hydrogen and for synthesis of titanium carbide during reaction of carbidization between titanium and carbon particles. Regularities of connection between HVED parameters and changes of dispersity and intensity of titanium carbide formation.

The effect of filler concentration of the powder mixture (Ti-TiC-C), synthesized by high-voltage electric discharge (HVED), on the thermal and mechanical properties of epoxy composites, was studied. Basing on the value analysis of destructive stresses in bending (σ), Young’s modulus (E), resilience (W) and heat resistant by Martens (T), a range of powder mixture (Ti-TiC-C) concentration, which allows to increase thermophysical and mechanical properties of epoxy composites for manufacturing equipment in conditions of alternating loads was set.

Ti and its alloys are mostly used for implant production. Their biocompatibility depends on the formation of thin TiO₂ layer on the surface. It can be improved by modification of oxide structure in tubular. For biomedical applications, the adhesion of the coating layers is essential. The aim of the present paper is to investigate the adhesion of TiO₂ nanocoatings on titanium surface.

Commercially pure Ti (CP Ti) and Ti-6Al-4V alloy samples were grinded, etched and anodized. The anodization was done in 0.5 wt.% HF electrolyte with duration of 7 hours for the CP Ti samples and 6 hours for Ti-6Al-4V alloy samples. The adhesion was investigated by tape and scratch tests. The critical loads that generate the first failures during the scratch test are used for characterization of the adhesion of the TiO₂ nano-tubular coating. The critical loads were measured by CSEM-Revetest macroscratch tester under progressive scratching mode. The samples were characterized by SEM and EDX analysis. The areas around the critical load were further observed by optical and scanning electron microscopy for detail inspection of failure mechanism.

It was established that the higher micro-roughness of the surface of CP Ti sample after anodization is responsible for the detachment only of small areas of the nano-tubular coating situated mainly on the top surface. The lower micro-roughness of the sample made of titanium alloy and the presence of large flat areas lead to detachment of large coating’s portions. The scratch test reveals that the TiO2 nano-tubular coating on the CP Ti fails at an early stage (Lc1 ~ 8 N; Lc2 ~ 26 N), while that on the Ti-6Al-4V sample undergoes cohesive failure and completely fails at higher load values (Lc1 ~ 13 N and Lc2 ~ 40 N respectively). As titanium alloy is ductile material with higher strength than the CP Ti, it provides better support for the coating and produces higher critical loads.