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

The study identifies the main casting defects at the interface between a cast iron ring insert and an Al-Si piston and determines their principal causes. Industrial investigations of 1000 pistons showed that the Al-Fin process increases Fe content in the AlSi9 alfining alloy, promoting long plate-like β-Al5FeSi phases and porosity in the joint region. Gas contamination by oxides and hydrogen further weakens the bond. The addition of approximately 0.05 wt.% Mn and intermediate re-refining of the AlSi9 alloy were found to improve the microstructure and reduce porosity, thereby increasing the quality of the insert-piston joint.

Dissimilar welding between duplex stainless steel and structural steel is increasingly used in the offshore, petrochemical and energy industries due to the combination of high corrosion resistance and good mechanical strength. This study presents a comparative investigation of two welding procedures for which they were used as filler metal: a BÖHLER Q G 309L-Si solid wire (GMAW 135 process), a FOX core 2209-T1 flux-cored wire (FCAW 136 process) and M21 shielding gas (82% Ar + 18% CO2). The butt joint was performed between 10mm thick plates made of duplex stainless steel UNS S32205 and structural steel S355J2. During tensile testing, failure occurred in the base material, confirming the high strength and good quality of the welded joints. Charpy impact testing revealed high toughness in the weld area for the GMAW 135 process, while excellent toughness was obtained for the GMAW 136 process. Hardness measurements showed a more uniform hardness distribution for the flux-cored wire welds and macrostructural analysis confirmed full penetration of both welds.

By utilizing the tools of the PyCALPHAD library and a thermodynamic database, Python-based software components were developed to calculate the energetic characteristics of phase transitions, enabling the prediction of Fe–W–C system behavior under varying composition and temperature. According to the CALPHAD calculation, it was established that within the temperature range of 500–2000 K for the composition of 43 at.% Fe, 43 at.% W, and 14 at.% C, an intermediate Fe3W3C phase is formed, which melts incongruently at 1770K.

Cultural heritage objects represent an essential component of human identity, history, and collective memory. However, monuments, artworks, manuscripts, archaeological artefacts, and historical buildings are continuously exposed to environmental deterioration processes, including humidity fluctuations, pollution, biological colonization, salt crystallization, and mechanical degradation. Conventional conservation methods often provide effective protection but may involve invasive procedures, limited durability, or the use of environmentally harmful chemicals. In recent decades, nanotechnology has emerged as a promising approach for sustainable conservation due to the unique physicochemical properties of nanomaterials, including high surface area, enhanced reactivity, photocatalytic activity, and the possibility of designing multifunctional protective coatings. This review discusses innovative nanomaterials used in cultural heritage conservation, including silica nanoparticles, titanium dioxide, zinc oxide, calcium hydroxide nanoparticles, graphene-based materials, and nanocomposites. Their applications in consolidation, cleaning, protection against pollutants, antimicrobial treatments, and sustainable preservation strategies are examined.
The report is under project No. KП-06-H90/6 dated 10.12.2024 on the topic: “Ecologically sustainable conservation strategy for written heritage” from the Scientific Research Fund, Competition for funding of fundamental scientific research – 2024. Supervised by Chief Associate Professor, PhD, MSc Eng. Iskra Tsvetanska.

The paper presents the research carried out for the development of brazing materials which, in a single pass, deposit two layers in the brazing joints: a buffer layer with high diffusion potential and increased silver content, and a filling layer with high strength and reduced silver content. The brazing performance of Ag20-type coated rods was improved by introducing a percentage of Ag40-type powder into the deoxidizing coating. The research was completed by establishing and patenting both the product formulation and the manufacturing process. The new product was successfully tested for producing brazed joints in copper pipes, copper-to-steel joints, and steel-to-tungsten carbide joints. The results of the mechanical tests met the required specifications, while the metallographic analysis of the joints showed an increase in diffusion of approximately 18.5% compared with the diffusion obtained using Ag20-type rods. The advantages of the brazing process using the new products consist of increased brazing productivity, improved quality of the brazed joints, and reduced environmental emissions from the resulting slag.

This article presents information about methods for evaluating the permeable materials based on metal powders mechanical and filtration properties. It describes methods for determining the permeability coefficient and local permeability coefficient, filtration fineness, and shear strength of powder materials, assessing the sintering quality of composite permeable materials containing fibers, and testing for strength under operating pressure differentials (up to 1 atm). The role of 3D-modeling in improving the efficiency of research is highlighted, enabling the rapid development and manufacture of fixtures for hermetically sealed specimens as their shape and size change.

Abstract: Thermo-reactive diffusion (TRD) coatings are formed on conventionally cast Ti6Al4V alloy using the pack cementation process to improve its surface characteristics. Aluminizing, siliconizing, and molybdenizing treatments are carried out at 700 °C, 1000 °C, and 900 °C, respectively, for 2 h using Al, Si, and Mo powder packs containing NH₄Cl as the activator and Al₂O₃ as the inert filler. The resulting coatings are systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) to investigate phase evolution, coating morphology, and elemental distribution. XRD analyses confirmed the formation of Ti–Al intermetallics (TiAl, TiAl₂, TiAl₃), Ti–Si silicides (TiSi, TiSi₂, Ti₅Si₃), and Mo-enriched Ti solid-solution phases within the coatings. Cross-sectional SEM observations have revealed continuous and well-adhered diffusion layers with thicknesses of approximately 20 μm for the aluminized coating and 50 μm for the molybdenized coating, while the siliconized layer (40 μm) exhibits a graded multilayer silicide structure. EDS elemental mappings have demonstrated inward diffusion of the deposited species and outward diffusion of substrate elements, confirming diffusion-controlled coating growth. The formation of metallurgically bonded reaction layers with compositional gradients is expected to substantially enhance the surface hardness, wear resistance, and high-temperature performance of the Ti6Al4V alloy. The results demonstrate that thermo-reactive diffusion by pack cementation provides an effective and controllable route for tailoring the surface microstructure of cast Ti6Al4V through appropriate selection of coating chemistry and processing conditions.

The high-temperature self-propagating synthesis (SHS) of carbides and borides in powder systems (30, 50, 70) wt.% (Fe-Ga)-(Ti-C) and (30, 50, 70) wt.% (Fe-Ga)-(Ti-B4C) was investigated at a temperature of 1200 °C in a neutral argon atmosphere. It was established that the introduction of a master alloy (Fe-55 wt.% Ga) into the initial mixture intensifies the SHS process. The appearance of a liquid phase at lower temperatures in gallium-containing systems is likely one of the main reasons for the activation of transport mechanisms for mass transfer to the chemical reaction front. Corrosion tests in a simulated seawater environment (3% NaCl solution) showed that simultaneous alloying of iron with gallium and boron significantly increases the corrosion resistance of iron-based materials. Specifically, the material containing 30 wt.% (Fe-Ga)-(Ti-B4C) demonstrated high protection (ASTM G-1, Good) in an environment close to seawater.

The article reveals a new method that relates to the treatment of active surfaces of agricultural working bodies, in particular harrow discs, by applying nanostructured coatings using atmospheric plasma jet spraying (APS). The process consists of preparing the surface by corundum blasting at a pressure of 5.5 bar, followed by preheating to 150°C and depositing a nanostructured powder of the WC-Co 88/12 type.
The technical novelty lies in the synergetic optimization of the deposition parameters: current intensity of 550 A, hydrogen flow rate of 9 L/min, spraying distance of 100 mm and a high scanning speed of 500 mm/s, under forced post-deposition cooling.
The technical result obtained by applying this process consists of creating a protective layer with porosity below 1.2%, adhesion of over 65 MPa and a hardness of 1150-1250 HV0.3, ensuring an increase in the durability of the working element of up to 2.8 times under conditions of severe abrasive wear.

Based on waste biogenic calcium carbonate CaCO3 and silicon dioxide SiO2, polyphase materials with a predominant content of calcium silicate phases and a limited presence of silicon dioxide were synthesized in laboratory conditions. When preparing the experimental samples, solid-phase synthesis and thermal treatment modes with a maximum temperature of up to 1300oC were used. During the X-ray phase analysis of the obtained experimental samples, the presence of Ca3(SiO3)3 pseudowollastonite (dominant phase) was registered, β-Ca2SiO4 and SiO2 cristobalite. The main possibilities for further expedient modification of the used technological regimes are analyzed. The prospects for potential application of the synthesized phases for the preparation of various functional materials are considered. The study is consistent with modern trends in the use of technological approaches that allow the utilization of waste materials.

This article summarizes the preliminary preparations for conducting experiments with phase change materials to determine their behavior during continuing heating and cooling processes. The goal is to summarize conclusions about the possibilities of using these materials in boilers and other water-heating tanks for industrial and domestic applications. The techniques, materials, and equipment that will be used are described, as well as the theoretical behavior of the materials that will be compared

Nickel-based nanocomposite coatings reinforced with silicon dioxide (SiO₂) nanoparticles are attracting increasing interest in advanced marine applications due to their superior mechanical properties and resistance to surface wear. In this study, selective Ni-SiO₂ nanocomposite coatings were prepared and investigated to determine the relationship between microstructure, composition, and mechanical properties. The microstructure of the coatings was investigated using scanning electron microscopy (SEM). The analysis showed that the matrix is fine-grained and relatively homogeneous, containing well-dispersed SiO₂ nanoparticles at an amount corresponding to the optimal reinforcement level. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed that silicon oxide had been successfully incorporated into the nickel matrix and was uniformly distributed within it, and no significant signs of agglomeration were observed in the most effective compositions. Mechanical properties were evaluated by scratch tests to assess the coating’s adhesion and resistance to mechanical damage. The results showed that SiO₂-reinforced coatings exhibit significantly higher scratch resistance and higher critical load values. This improvement is attributed to dispersive strengthening, grain refinement, and the barrier effect created by hard ceramic nanoparticles, which together inhibit plastic deformation and crack propagation. In summary, the results of the study demonstrate the potential of Ni-SiO₂ nanocomposite coatings as durable protective solutions in marine environments, where resistance to mechanical wear and surface damage is particularly important. The study provides insights into how to adjust the microstructure and reinforcement distribution to improve the coating’s performance characteristics.