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

The effect of different heat treatments on the microstructure and mechanical properties of the C45 and S355J2 steel forgings has been presented. Samples of the same forgings, but subjected to the different heating treatments, were prepared and tested by using opticalmicroscopy, tensile machine, and hardness tester. It was observed that the requested mechanical properties of the forgings and uniform structure can be achieved by determining the appropriate heating treatment parameters.

Due to the mechanical properties (toughness, elongation, tensile strength) that characterize ductile iron, its application in foundry technology is becoming more pronounced every day. The chemical composition and heat treatment of ductile iron have a great influence on the required mechanical properties. Given the operating conditions, the main purpose of heat treatment of ductile iron is to change the desired mechanical properties. Since the specific mechanical properties of ductile iron are generally related to the regularity of the mined graphite nodules, the main objective in production is to produce ductile iron with the highest possible percentage of ductility. In the experimental part of the paper, microstructure and hardness tests were carried out on specimens of ductile iron NL 400 and NL 700 before and after heat treatment by soft annealing (ferritization) and improvement. It was found that the type and corresponding parameters of heat treatment significantly affect the microstructure and the achieved hardness values of the ductile iron test specimens.

In this work are presented the development of simulation metods of analysis the phase-structural transformations and properties in alloy steels. The analytical dependencies of this simulation were applied to the calculation of ferritic, pearlitic and bainitic transformations in carbon and alloy steels. To calculate the amount of martensite, the authors used a new equation that has been successfully used in others works too. Based on the developed regression model, isothermal and structural diagrams for 20CrNi4V and 25Cr2Mo1V steels have been constructed. The analysis is performed of the aerial quenching of tools from alloy steels 20CrNi4V and 25Cr2Mo1V, according to the recommended heat treatment schedules in the tools production. For steels 20CrNi4V and 25Cr2Mo1V, it is possible to obtain a bainitic structure in a wide range of cooling rate. Corrections of heat treatment schedule were proposed.

A series of piston hypereutectic silumin based on Al – (15÷20) % Si, alloyed with copper, magnesium, nickel, chromium is investigated. The mechanical characteristics of ingots from experimental alloys were determined: temporary tensile strength, hardness, relative elongation depending on the composition of the alloys, and temperature coefficient of linear expansion (TCLE). It is shown that the tensile strength of forged blanks is 1.5-2.4 times higher than ingots of hypereutectic silumins. The resulting structure of forgings ensures their high plasticity (relative elongation δ = 5.7÷7.5%; relative narrowing Ψ = 10.3÷14.2%). The optimal mode of heat treatment of deformed silumin is determined: quenching from step heating and aging, which allows increasing the strength of forgings up to 370-470 MPa. Moreover, the plasticity indicators remain at a high level, and the average thermal expansion coefficient of the alloys is (18.0 ÷ 19.2) · 10-6 K-1 in the range of 50 ÷ 200 ° C.

Electrolyte plasma processing is environment-friendly and high-effective method to treat surfaces of metals and alloys and can be used for heat or thermochemical treatment as well as for cleaning or polishing of metal surfaces. Modes of processes in the electrolytic cell for different metals can partially overlap. So it is possible to perform the same or different processing for different metals (including components of bimetal) simultaneously. This article describes modes to be established at the active electrode during the anodic process, and application of these modes to various types of treatment of bimetals. It is shown that there exists an option of separate or simultaneous heat or thermochemical treatment, as well as polishing of one or both surfaces of bimetals.

During the injection molding procedure of plastics, the gear pumps in their work are exposed to the effect of elevated pressure and temperature. On one of these pump there has been frequent downtime due to breakage of the driven gear. Gears which were installed as standard spare parts had stood out in operation for three months. On a sample of a broken gear were perfomed laboratory examinations (metallographic examinations, hardness control on cross-section and surface of the fracture was examined). Conclusion was that it was high quench hardening of a steel of which a part is made, the most likely cause of the fracture of a standard gear. In order to extend the useful life, two test gear are made from steel for cementation 20MnCr5. By applying the appropriate parameters of thermal chemical treatment useful life of the gear is significantly extended, after which the test gears have worked for nine months from the moment of installation.

The work is devoted to the study of evolution of flaws in aluminium alloys of Al-Zn-Mg-Cu, Al-Cu-Mg-Мn alloying systems and to the determination of their connection with structural factors of the material such as the size and composition of intermetallic phases conditioned by heat treatment tempers, and also to the study of the effect of big number of physical factors on the long-term behaviour of structural elements of aluminium alloys, and to the determination of the rate of formation of corrosion damages in structural elements of the aircraft wing

Cane chains are very important transmission elements which are carefully designed according to fatigue strength and wear resistance. To increase the life of cane chains, the resistance of the surface failure should be increased. In this investigation, experiments were carried out to evaluate the wear resistance using wear test rig designed and manufactured for this purpose. Three types of steels were used, namely 16MnCr5, 17CrNiMo6, and 18MnCrB5. Discs manufactured from these steels were carburized for different periods of time (6, 10, and 12 hours). Tempering process was carried out at different temperatures to obtain hardness values of 48, 52, and 56 HRC. The accumulated weight loss was measured and the wear rates were determined for each case hardened steel at the constant normal test load of 800 N. The accumulated weight loss was measured as a function of the number of revolutions. Wear rate was calculated and presented with case hardened depth and hardness for all steels. The hardness distribution and carbon content of carburized layer was presented as a function of the distance from the surface. Carburized layer microstructure and carbide percentage were presented and measured. From test results, it was concluded that the wear rate for all steels under investigation decreases with the increase of their case hardness. Minimum wear rate was obtained at hardness 56 HRC. Wear rate for all steels decreases with the increase of carburizing time tending to reach a minimum at carburizing time 10 hours. Wear rate for steel 16MnCr5 is less than that of the wear rate for 17CrNiMo6 and 18MnCrB5 by about 15℅ and 45℅ respectively under the same testing conditions. Carburized layer, carbon content and case depth increase with the increase of carburizing time.

This study explores the metal of a coating deposited by a high-chromium flux-cored wire alloyed with a BN-TiB2-ZrB2 complex. We investigated the changes in the durometric properties and fine structure of the coating after tempering and subsequent quenching. It is shown that the hardening of the metal of such a coating after quenching consists in the formation of a complex composite structure with an iron-chromium martensitic matrix, a large amount of eutectic and particles of hardening complexes, which leads to an increase in hardness and wear resistance. It has been established that phase transformations in the metal of such a coating are caused by the formation of an eutectic component based on chromium and iron borides, a framework structure and a large number of dispersed titanium nitride particles up to 2.5 μm in size.

The purpose of this research work is to determine the influence of the carbide phase and the austempering temperature on the mechanical properties of carbide-bainite ductile irons. Two groups of irons have been investigated: austempered at 300°, with a lower bainite structure, and at 400°, with an upper bainite structure. Tensile strength, yield strength, elongation, impact strength and hardness have been tested tested.

Quantitative analysis of the phase composition of the Ti-Al-V-Mo-Zr system alloys was carried out during operation using the Thermo-Calc program (TCW5 version, TTTI3 database). Polythermal and isothermal cuts are plotted, design temperature values of liquidus, solidus and transition into β-field during heating are given. Regarding the titanium alloy of the Ti-Al-V-Mo-Zr system the effect of annealing temperature on the microstructure of the alloy as well as on the alloying elements content in α and β–phases was studied using the scanning electron microscopy method.

Quantitative analysis of the phase composition of the Ti-Al-V-Mo-Zr system alloys was carried out during operation using the Thermo-Calc program (TCW5 version, TTTI3 database). Polythermal and isothermal cuts are plotted, design temperature values of liquidus, solidus and transition into β-field during heating are given. Regarding the titanium alloy of the Ti-Al-V-Mo-Zr system the effect of annealing temperature on the microstructure of the alloy as well as on the alloying elements content in α and β–phases was studied using the scanning electron microscopy method.