Metal matrix nanocomposites (MMnCs) comprise a metal matrix filled with nanosized reinforcements with physical and mechanical properties that are very different from those of the matrix. In ZA-27 alloy-based nanocomposites, the metal matrix provides ductility and toughness, while usually used ceramic reinforcements give high strength and hardness. Tested ZA-27 alloy-based nanocomposites, reinforced with different types (SiC and Al 2 O 3), amounts (0.2 wt.%, 0.3 wt.%, and 0.5 wt.%) and sizes (25 nm, 50 nm, and 100 nm) of nanoparticles were produced through the compocasting process with mechanical alloying pre-processing (ball milling). It was previously shown that the presence of nanoparticles in ZA-27 alloy-based nanocomposites led to the formation of a finer structure in the nanocomposites matrix and an improvement in the basic mechanical properties (hardness and compressive yield strength) through the enhanced dislocation density strengthening mechanism. Solid particle erosive wear testing demonstrated that these improvements were followed with an increase in the erosive wear resistance of tested nanocomposites, as well. Additionally, by analyzing the influences of type, amount, and size of nanoparticles on the erosive wear resistance of nanocomposites, it was demonstrated that there is an optimal amount of nanoparticles, which in our case is 0.3 wt.%, and that the presence of SiC nanoparticles and smaller nanoparticles in nanocomposites had more beneficial influence on erosive wear resistance.

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The objects of this work were nine different copper-based friction linings produced from powder by pressing and sintering. Six copper-based friction linings contained 3 wt.% zinc (Zn) and variable content of tin (Sn), i.e. 1, 2, 4, 6, 8 and 10 wt. %. Three copper-based friction linings were with fixed contents of Zn (3 wt.%) and Sn (10 wt.%), and with different amount of SiC particles, i.e. 2, 4 and 6 wt.%. Tribological studies on these friction linings included determination of the static and kinetic coefficient of friction under different normal loads and unlubricated sliding conditions, as well as, determination of the abrasive wear resistance under different normal loads and unlubricated sliding/rolling conditions. The analysed results present the influence of Sn content and addition of SiC particles to the copper-based friction lining on its friction and wear properties.

In the present work, abrasive and erosive wear of wear-resistant composite coatings with a complex structure and different phase compositions deposited on titanium surfaces was studied. The coatings were obtained by electrospark deposition (ESD) using two types of hard-alloy compositions: WC–TiB2–B4C–Co–Ni–Cr–Si–B and TiB2–TiAl reinforced with dispersed nanoparticles of ZrO2 and NbC. The influence of the ESD process parameters on the roughness, thickness, composition, structure and coefficient of friction of the coated surfaces was investigated, and their role in protecting the titanium surfaces from wear was clarified. Dense coatings with the presence of newly formed wear-resistant phases and crystalline-amorphous structures were obtained, with roughness, thickness and microhardness that can be varied by the ESD modes in the range Ra = 2.5 ÷ 4.5 µm, δ = 8 ÷ 30 µm and HV 8.5 ÷ 14.0 GPa. The new coatings were found to reduce the abrasive and erosive wear of the coated surfaces by up to four times. The influence of the geometric characteristics, composition and structure of coatings on the wear intensity and wear resistance of coatings was studied.

The aim of the present work is to identify and formulate the basic principles and approaches for the selection of materials for electrical spark and gas-flame stratification of structural steels. For this purpose, have been examined: -The characteristic features and physical foundations of the two methods, the changes in the composition and structure of the coating materials in the transfer process and in the formation of the coatings and the general similarities and differences.-The regularities of formation and qualitative characteristics and properties of the coatings obtained, depending on the process parameters of the coating mode and the layering material.-The interrelation between: the process parameters of the application system; the coating material; the quality characteristics, the composition, the structure of the coatings; the mechanical and the tribological properties of the coatings. The requirements for coatings have been formulated for various loads and wear cases and on this basis the requirements for the layering materials are determined by the two methods. Appropriate materials and compositions are specified for various cases of friction and wear. The main approaches to the selection of the layering materials are described.

In this work contactless local electro spark deposition (LESD), has been used to received wear resistant coatings from hard alloys based of ТiC, TiN, TiCN onto high speed steel HS6-5-2. The influence of the operating electric parameters and the electrode materials on the roughness, thickness, microhardness, phase composition, and on the structure of resulting coatings was studied. The impact of different electrode materials on the quality characteristics, the composition and structure of the resulting coatings has been found. The technological parameters of the LESD process for the formation of coatings with a predefined roughness, thickness, composition and structure has been determined.

At present, tribological studies are dominated by empirical and statistical approaches. Regardless of the availability of some standardized methodologies and devices, unique designs, taking into account the variety of conditions affecting friction and wear mechanisms, are being developed. This circumstance makes it difficult to analyze and compare the experimental results of individual authors. The complexity of creating a unified approach in tribology is due to the mutual influence, change and distribution of contact structures and parameters in the friction process, as well as the difficulty of measuring them in the friction process itself. The objectives of this study are: to identify the main mechanisms and patterns of friction and wear of contact systems lubricated with vegetable oils and vegetable-mineral compositions, with new synthesized antifriction and anti-slip additives, and to identify and scientifically establish opportunities for triggering self-organizing processes in contact that have an effect low friction and wear, and especially friction without wear. This article presents an initial overview of the current state of research in the field of the use of biodegradable lubricants for friction units of machines and mechanisms. It was concluded that the task of developing a lubricant with simultaneously high tribological characteristics, resistance to operational influences, extremely low toxicity, and high biodegradability remains urgent to this day.

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