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

In this study, the tribological behavior of new generation cast irons (SiNb and SiW) developed as an alternative to cast irons containing high silicon and molybdenum (SiMo) is investigated under dry friction conditions. All cast irons are produced by sand mold casting as Y blocks according to ASTM A536-84 standard and metallurgical characterization studies have revealed that they all have spheroidal graphite and dispersed carbides like Mo-rich M6C, Nb-rich MC and W-rich M6C type depending on the alloying element, within a ferritic matrix. Although no significant change is observed in the spherical morphology of graphite in cast iron matrices, a significant change is observed in the amount of graphite and image analysis studies reveal that the graphite content (area-%) in SiNb and SiW cast irons is 4,02 and 4,30, respectively, compared to SiMo cast iron (5,80). A significant change in the hardness of cast irons is also determined depending on the microstructural features; SiNb (228 ± 7 HV10) and SiW (218 ± 5 HV10) cast irons have higher hardness values compared to SiMo cast iron (192 ± 5 HV10). Cast irons and alumina ball as counterpart material are subjected to a tribological interaction for 150 m under dry friction conditions at a nominal load of 10 N and a ball sliding speed of 0.08 m/s and the findings indicate that (i) the coefficient of friction (CoF) decreases as the graphite content increases, with SiMo having the lowest CoF (0.023), followed by SiW (0.025), and SiNb showing the highest CoF (0.040), (ii) the specific wear rate increases as the hardness decreases, therefore, SiMo has the highest specific wear rate, whereas SiNb demonstrates the lowest specific wear rate and (iii) adhesive wear is the dominant wear mechanism for all ductile cast irons due to the presence of their ferritic matrix.

This paper discusses contact interaction under mechanical stress and how vibrations change the physical properties of conductor materials, which affects their ability to provide reliable contact. It also analyzes the causes of contact failures, which allows us to better understand the mechanisms that lead to problems in the operation of electrical connectors. These factors can lead to serious consequences, including breakage and reduced reliability of connectors, and also considers the possibilities of improving the characteristics of electrical contacts at the stage of their creation, using various technologies for applying and creating an approximately ideal molecular structure of the contact surface of detachable electrical connectors, with an increase in the surface layer of the contact and a decrease in the coefficient of friction.

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 paper presents experimental work focused on the wear resistance of clads made with OPEN ARC technology (MOG) and clads with cycled cladding nozzle. The distribution of carbide phases by electron beam was evaluated. The influence of the tempering temperature of the clads on the hardness of the layers was determined. Tests of the resistance of the clads to abrasive wear were carried out.

The paper presents the results of research aimed at determining selected tribological properties of PVD nanocoatings. PVD nanocoating of the 4th generation duplex nACRo4 was applied to the surface of shaped parts of molds and cores for high-pressure aluminium casting. The surfaces were laser textured with a random texture. The tribological properties of the coating were determined by measuring the friction coefficient using the Pin on Disc method at a temperature of 300 °C. Confocal microscopy was used to determine the parameters of the microgeometry of surfaces with random texture topography. The aim of this surface treatment was to analyse the adhesion effect of commercially used ones of lubricants in the technology of treatment of shaped parts of molds when casting aluminium alloys under high pressure on machines with a cold filling chamber. By checking the integrity of textured surfaces with deposited with the duplex PVD coating of the 4th generation nACRo4, no damage to the integrity of the deposited material was detected PVD coating. Elements forming the PVD coating were detected on the surface by semiquantitative EDX microanalysis.

Investigations of wear resistance and tensile strength of steel products with diffusional zinc coating obtained in zinc powders with a nanocrystallized surface of powder particles were carried out. The effect of the structural state of the coating on the wear resistance and adhesive grasping with a steel counterbody was established. The prospects of the nanogalvanizing process to improve the strength of steel products are shown.

The development of technologies in modern machine building aims at improving the mechanical and technological properties of the materials. The present study presents an improvement in the mechanical properties of low carbon steels by thermoffusion coatings with nanofibers obtained under different heat treatment regimes. Depending on the type of heat treatment and the size of the zinc particles, different gradient layers can be obtained in depth. This of course reflects positively on the chemical resistance of the material. In addition, it positively affects the mechanical properties of the material by increasing mechanical strength and technological properties by improving the resistance to plastic deformation. With these first studies, there is an impetus for another look to improve the properties of low-carbon steels that are widely applicable in the field of machine building.

In the article the new solution of friction measurements for the sliding friction coefficient innerducts housing fibre optic microcables, catheters, cannulas are presented. The measurements and studies will significantly contribute to broaden the scope of studies in tribology for elements of various designs and materials undergoing sliding interactions. Moreover, the device enables analyses of diverse cross sections and dimensions to be carried out, all at one testing station and retooling time of 10 minutes. The invention allows scientific research to be carried out, novel materials to be designed and new materials for sliding layers to be effectively selected. The application of the invention reduces costs of analyses of innovative products by 55%-70% in relation to those used at present.

For the purposes of testing tribological characteristics of the stainless steel X20Cr13 designed for the parts of process industry plants for the production of sunflower oil, test samples were made and heat treatment by improving on different hardnesses was performed. Final machine processing of the samples was performed out by grinding and polishing. This way, the different characteristics of the surface layer and the different surface topography were achieved. The paper presents the results of the impact of the hardness on characteristics of the stainless steel X20Cr13. By examining the resistance to the adhesion wear it was concluded that the higher wear was on the test samples which have been in the raw condition and who were also loaded by higher forces. Therefore, the quality of the surface wear greatly affects the surface roughness and the coefficient of friction.