Scientific Technical journal ‘’Metal Science and Treatment of Metals’’

The effect of heat treatment on the structure, microhardness and hardness of white cast iron

A. Yu. Borysenko — 2026-09-28

This article presents the results of a study of the microstructure, microhardness, and hardness of unalloyed white cast iron after heat treatment with phase recrystallization using a normalization regime and accelerated cooling with compressor air at pressures of 0.2 and 0.6 MPa. The greatest increase in white cast iron hardness (from 74 to 79.5 HRA) occurs after heat treatment with compressor air cooling at a pressure of 0.6 MPa.

It has been shown that all heat treatment conditions lead to an increase in the microhardness of pearlite and cementite in the ledeburite structure, however, with different patterns for these structural components. The increase in pearlite microhardness occurs due to an increase in its dispersion and correlates with an increase in the cooling rate. No changes in the cementite microstructure after heat treatment are observed using conventional metallographic methods. Unlike pearlite, the change in cementite microhardness does not correlate with a change in the cooling rate. The increase in cementite microhardness occurs due to an increase in its minimum values before heat treatment. Significant heterogeneity in cementite microhardness was established, which is considerably higher than that of pearlite. Heat treatment with different cooling rates resulted in the formation of similar values for the maximum, minimum, and average microhardness of cementite.

It is suggested that the observed features of the change in the microhardness of cementite are associated with changes in its micro- and/or substructure, not detected by the applied research methods or its different chemical composition.

Market Overview of Lost Foam Metal Casting and Forecast of Its Growth Until 2033 with Prospects of Development and Technology Digitalization

I. A. Nebozhak — 2026-09-16

The article presents a comprehensive analysis of the current state, macroeconomic trends, and technological prospects for the development of the Lost Foam Casting (LFC) process, dedicated to its 70th anniversary. Based on current monitoring data from global analytical agencies Grand View Research and Precedence Research, a stable expansion dynamics of the global LFC market is demonstrated, with a projected compound annual growth rate (CAGR) of 7.2% up to 2033. This growth is driven by the modernization of industrial production lines and the global transition to Industry 4.0 standards. Particular attention is paid to the scientific and technological experience of the Physico-Technological Institute of Metals and Alloys of the NAS of Ukraine in the field of digital transformation of pattern production. The concept of introducing additive manufacturing methods, specifically 3D printing of porous polymer patterns, is considered, which allows eliminating the capital-intensive and time-consuming stage of designing and manufacturing traditional metal tooling (molds). A significant advantage of integrating 3D-printed patterns is justified in terms of the absence of the need to recertify existing foundry shop structures, since the metallurgical essence of the casting process and the certification criteria for the final castings remain unchanged. The unexploited potential of the physicochemical and technological factors of LFC is revealed, including methods for regulating heat dissipation through vacuuming the dry sand mold, the possibility of differentiated heat treatment during melt crystallization, and obtaining ultralight frame-cellular structures based on topological optimization algorithms and artificial intelligence. The features of creating cast-reinforced structures for transport engineering with the integration of strengthening frames up to 15% by weight of the casting directly into the pattern body are described. The specific nature of gas-hydrodynamic processes during intense gasification of the polymer in the contact zone with the reinforcement is highlighted. To stabilize gas pressure, a methodology for controlled gas venting via a system of additional ventilation channels is proposed, ensuring both an increase in the geometric accuracy of castings and a high environmental effect due to the neutralization of hydrocarbon compounds.

Background and development of a high-silicon aluminum piston alloy. Part 1. piston alloys in the automotive industry of well-known world companies

V.I. Belik — 2026-09-15

Increasing the efficiency and reliability of heavily loaded forced diesel engines operated in extreme thermally stressed conditions requires materials that ensure long-term stable operation of the piston pair at temperatures of 200–400 °C. In world practice, this is achieved by using hypereutectic aluminum alloys with a silicon content of 22–26%, the main advantage of which is a significantly lower coefficient of thermal expansion at high temperatures compared to hypoeutectic and eutectic piston alloys. According to the domestic standard for foundry aluminum alloys (DSTU 2839-94), only one alloy has a maximum silicon concentration of 22%.

The increase in the power of engines produced at Ukrainian enterprises, the approximation of their technical characteristics to European and world indicators necessitates the search for new solutions for the creation of an economically alloyed alloy of increased wear resistance, with the lowest possible thermal expansion, which is usually achieved by increasing the concentration of silicon. In the work, the solution to this problem was carried out on the basis of more than a century of experience of leading manufacturers of piston alloys. For this purpose, a systematization of alloys with a silicon content of 11 to 26%, used in the automotive industry of well-known world companies, was carried out. The features of their chemical composition and mechanical characteristics were analyzed in accordance with the range of operating temperatures. Among the 35 alloys considered, only four are high-silicon (> 22%), and the compositions of three of them coincide, which reduces the amount of information useful for substantiating the composition of the new alloy. Since three dozen piston alloys with a lower silicon content have proven their effectiveness at lower operating temperatures, when creating a new alloy, not only the ratio of silicon and alloying components, but also these components among themselves were studied. The traditional approach of searching for relationships between composition and properties did not yield results due to significant differences in the content of alloying components in alloys with the same silicon concentration. This necessitated the development of a new analysis method that takes into account the differences in the chemical composition of all known piston alloys. The peculiarity of the method and the effectiveness of its application will be considered in the second part of this article, and the structural-phase analysis of the alloy created using the original method will be considered in the third, final, part.

Hybrid surface treatment technologies based on the electrospark alloying method

O.P. Haponova — 2026-09-15

The formation of functional coatings is one of the promising approaches to improving the durability, hardness and wear resistance of machine parts and tools. Electrospark alloying (ESA) has proven to be an effective technology for local surface modification, offering minimal thermal impact, high adhesion and the ability to use a wide range of conductive materials to produce coatings with tailored properties. At the same time, further improvement of ESA is closely linked to the development of hybrid technologies that expand coating functionality and eliminate the shortcomings of individual methods.

The paper reviews the current state of ESA technology and analyzes the main schemes for its combination with other processing methods. Special attention is given to integration with surface plastic deformation, laser treatment, metal-polymer materials, and magnetron sputtering. It is shown that these combinations allow the formation of coatings with higher microhardness, wear resistance, corrosion resistance, controlled roughness, and improved tribological characteristics. Industrial aspects of implementing hybrid technologies are also considered.

Key challenges are identified, including the multiparametric nature of hybrid treatments, the complexity of controlling the stress-strain state, the need for mode optimization, and the lack of real‑time automated control systems. The use of machine learning for predicting coating properties, intelligent parameter selection, and adaptive process control is proposed. The main directions for further research are outlined: quantitative optimization of hybrid processing parameters, development of physical and mathematical models of coating formation, analysis of residual stresses and long-term operability in real conditions, and creation of digital decision support systems. The implementation of these tasks will facilitate the transformation of ESA‑based hybrid technologies into highly effective surface engineering tools for a wide range of industrial applications.

The influence of pulsed electric current modes on the structure and properties of the composite system W-steel Kh18N10T

V. A. Shalomeev — 2026-09-28

The work investigates the influence of technological parameters of roller contact welding on the formation of a metal matrix composite material reinforced with tungsten fibers. To assess the quality of consolidation of the composite structure, it is proposed to use the electrical conductivity measured by the eddy current method as an indirect indicator of the integrity of the melted zone and the volume fraction of internal defects. It is established that an increase in electrical conductivity corresponds to a decrease in the number of non-melts and the formation of a continuous conductive path in the fusion zone. To optimize the process of manufacturing the composite material, a fractional factorial experiment of the type 2⁵⁻² was implemented with variations in the duration of the welding current pulse, the duration of the pause, the force of electrode compression, the speed of formation and shear of welds. Based on the results of statistical processing of experimental data, an adequate regression model was obtained that describes the dependence of electrical conductivity on the technological parameters of the process. The area of optimal composite formation modes was determined by the steep ascent method. Metallographic studies have shown that the optimized parameters ensure the formation of a continuous molten zone around the reinforcing fibers while preserving the original microstructure of the surface layers of the matrix. It was established that the high-temperature short-term strength of the obtained composite materials at 1200 °C corresponds to the values calculated by the rule of mixture. Based on a comprehensive analysis of the microstructure and technological characteristics, a rational mode of forming a metal matrix composite material was substantiated.

Research Design Based on a Digital Twin for Refining the Melt of AK12 Aluminium Casting Alloy

D. S. Moroz — 2026-09-28

The article presents a scientific and technical proposal for a comparative experiment aimed at assessing the effect of refining the melt of AK12 aluminium casting alloy on the structural state, porosity, density and mechanical properties of shaped castings. The relevance of the study is determined by the fact that the quality of silumin castings depends not only on the standard chemical composition but also on the metallurgical cleanliness of the melt, including hydrogen saturation, oxide films and non-metallic inclusions. To plan further full-scale heats, a digital formulation of the study is proposed. It describes four technological series: a control heat without special refining, flux treatment, argon purging, and combined flux-gas treatment with filtration. The methodology includes spectral control of chemical composition, quantitative metallography, hydrostatic density determination, fracture analysis, hardness measurement and tensile testing. The model digital twin is used as a preliminary computational tool for formulating a hypothesis, determining expected ranges of indicators and preparing a verification programme. The predicted trend shows a decrease in area porosity, an increase in relative density and an improvement in ultimate tensile strength when moving from the control series to the combined treatment scheme. It is specifically emphasised that the numerical values presented in the manuscript are synthetic digital-twin data. They must be replaced with actual heat logs, metallographic results and mechanical testing protocols before the results can be submitted as a completed experimental study.