Key Engineering Materials Vol. 836

Abstract: The article presents the fractal approach to the study of the five peat structure samples. Digital images from natural porous raw peat, intended for fractal studies of the porosity, are proposed. Peat active porosity is used in this study. In this study, the peat active porosity, fractal dimension (D), and their relationship with different peat samples were investigated in an experiment. The results of this study demonstrate that a fractal dimension analysis of peat compositions texture is a useful method for the quantitative description of the active porosity. The received results should be considered in the theoretical and pilot studies connected with physicomechanical processes occurring on the porous surfaces of peat raw materials during its mechanical processing.

Abstract: This paper proposed a new method for processing titanium alloys based on preliminary plastic impact. The reasons for the deterioration of the surface roughness of titanium alloys during machining are considered. This problem lies in the formation of outgrowths on tool cutting wedge, which leads to the cutting process taking place as in the titanium-titanium pair. The adsorption phenomenon leads to the fact that the outgrowth is saturated with gases from the environment, and a thick oxide film is formed. As a result, high temperatures arise during machining from 1100 to 1200°C, increasing the cutting forces P and friction Q, which introduce the technological system into an unstable self-oscillating process. The problem posed eliminated by the method of preliminary plastic deformation, which forms a local inhomogeneous structure. At the stage of processing the titanium billet, the cutting edge enters the region with a heterogeneous structure, destroying the chips and growth with an oxide film. Since most of the temperature, about 80% takes away with the chips, the amplitude of the self-oscillating process decreases, which reduces the surface roughness of the processed titanium alloys.

Abstract: The paper considers the implementation of magnetic-abrasive finishing in the conditions of digital technologies, in particular within CNC systems. The process was implemented through the development of a special device for MAF based on vertical processing center with CNC – Emco Concept Mill 250 and the definition of the combination of working motions of a billet in the interpole space of a magnetic system and their speeds. The result of the study are optimal combinations of working motions and their speeds taking into account formed surface roughness and processing efficiency.

Abstract: This article deals with comparative analysis between thermoplastics and thermosets polymer materials. The problems of the choice of the polymer matrix and reinforcement filler in the manufacture products are made of polymer composite materials (PCM) for the oil industry are considered. Based on the analysis of existing types of polymer matrix and reinforcement fillers to maximize the requirements for PCM products for the oil and gas industry, a polyphenylene sulfide feed was proposed as a polymer matrix, and a unidirectional carbon fiber was used as a reinforcement filler. The results of laboratory tests of samples made with the help of melt impregnation and automated fiber placement technologies are presented.

Abstract: The set of studies on modified superficial layer friction pair parts made of X155CrVMo12-1steel was discussed. The said layer is produced according to the duplex process of nitriding and oxidation and is investigated using methods of metallography, X-ray diffraction analysis and micro-hardness measurement based on the oblique and transverse polished sections of the studied surfaces. The results produced proved the duplex process efficiency.

Abstract: The paper analyzes the structure of coal beds. It is noted that coal beds belong to laminar massifs with characteristic oriented structure and pronounced anisotropy of strength properties, and include rock layers and consolidated hard inclusions. The quality criteria of the coal loosening process are highlighted. A selective method of separating coal from a massif by cutting along weakened surfaces is proposed as an alternative to the existing combine technology with continuous cutting of a massif from the surface.

Abstract: The article presents an X-ray fluorescence analysis of chalcogenide glassy semiconductors. The standard method is applied to determine the concentration of arsenic, selenium, and sulfur in alloys. This technique, the quantitative composition of the glasses is defined with an accuracy of ± 0.0002.

Abstract: The article deals with topical issues of studying the physical, mechanical and tribological parameters of the surface layer of machine parts subjected to laser processing. Various options for modifying mating surfaces are evaluated and analyzed. The data of microstructural analysis and indicators of wear resistance are presented. A theoretical model of the wear of heat-strengthened surfaces is proposed, explaining the mechanism for increasing their wear resistance as a result of homogenization of the microstructure of a special surface layer with increased bearing capacity. It is experimentally confirmed that the greatest wear resistance is observed in friction units during mutual modification of mating surfaces.

Abstract: The article focuses on the topical issues of studying the microstructure, physical-and-mechanical and tribological parameters of the surface layers of a “ring-cylinder liner” friction pair subjected to laser processing. The analysis of the main defects of the elements of the cylinder-piston group of the internal combustion engine, methods for their recovery and increase of tribotechnical characteristics has been carried out. It is noted that the most effective means of increasing the wear resistance of the “ring-cylinder liner” friction pair are various types of heat and chemical-heat treatment of the working surface of the link. As a result of tribological studies, it was found that there is an increase in the wear resistance of a “ring – cylinder liner” friction pair in all the investigated laser exposure modes, taking into account the identified boundary processing conditions for one and the other interfacing elements. The maximum value of wear resistance is observed during laser thermal strengthening of both mating surfaces, at critical levels of laser energy density, which do not cause melting and microcracks in the surface layer. In this case, the wear resistance of the modified surface of the cylinder liner can increase 4.5...5 times, and more than three times for the piston rings.

Abstract: The paper reflects the relevance of hardening the working surfaces of the tool, where the surface layer plays a fundamental role. The main factors determining the wear resistance of the tool and their influence on the quality of the processed surface are analyzed. The purpose of the research is to study the effect of laser modification of tool alloys on wear resistance and on the roughness parameters of the machined surface. A small-sized drill bit (steel P6M5) and carbide inserts T15K6 are used as objects of research. The paper presents the results of experimental studies on the impact of laser radiation on the microstructure of materials, indices of wear resistance and quality parameters of the treated surface. It is established that there is a certain relationship between these indices. The modes of laser modification of the tool most acceptable for practical use are determined. Along with an increase in the wear resistance of a metal-cutting tool, a manifestation of the effect of an increase in surface roughness indices is found and experimentally confirmed. It is established that hardening of the surface layer is caused by structural and phase transformations with enhanced physical and mechanical properties, and the roughness indices depend on the degree of dispersion (amorphization) of the modified layer.