Key Engineering Materials Vol. 887

Abstract: The article is devoted to tribological studies of a ceramic composite with a zirconia-based die in order to replace carbide wire drawing dies with ceramic. Sliding friction was done according to the scheme finger-disk without lubrication and with lubrication. The wear rate and friction coefficients were determined, on the basis of which it is proposed to produce portage dies-blanks from zirconium ceramics. The influence of sintering temperature on the mechanical properties of ceramics, especially cracking resistance, was studied. The optimum sintering temperature was determined by the criterion of fracture toughness. The formation of defects after the final firing was investigated. It was found that sintering at a temperature of 1600 ° C is more promising. An trial batch of zirconium ceramic dies showed positive results in the process of drawing copper wire in industrial situations.

Abstract: The threshold of optical breakdown of the nickel alloy ChS57 (Inconel) was measured at a wavelength of 0.355 μm with a laser pulse duration of 10 ns. Heat treatment of ChS57 above pulse energy density threshold (1 - 2.5 J/cm²) occurred mainly in the ablative mode with almost no melting. The elemental composition of the surface layer did not change at an irradiation in a fixed spot. When a laser beam moves along the surface of the sample at a speed of 1 mm / s and at pulse energy density of about 0.02 J/cm², oxygen was detected in the elemental composition (3 – 4 wt. %). However, the proportions of the elemental composition of the alloy remained virtually unchanged. Heat treatment under threshold at pulse energy density ≥ 0.25 J/cm² revealed a rise of the surface layer with traces of high-temperature plastic deformation in the form of slippage on grain boundaries and crystallographic slip.

Abstract: This research aims to study boron-based coatings on the surface of steel parts. The significance of this topic is determined by practical considerations of the need to improve strength of the steel surface subjected to high loads. In the course of study, samples of strengthening coatings made of 65G steel obtained by HFEC heating method were created. Then, the samples were subjected to a series of studies using a metallographic microscope, as well as a measuring system based on eddy current effects. The obtained data analysis allows us to conclude about the pattern of electrical conductivity distribution on the surface of test materials with different coatings depending on the quantitative composition of flux when creating boron-based strengthening coatings.

Abstract: The article discusses the effect of the surface conditions on the corrosion resistance of alloys based on cobalt, titanium and stainless steel, which are currently used for the manufacture of components for implantable medical devices. It is shown that an increase in surface roughness has practically no effect on the corrosion resistance of alloys based on cobalt and titanium.

Abstract: In this paper the temperature fields in the zone of processing of paint coatings by laser radiation of a sample of the metal skin of aircraft gliders with selective (layer-by-layer) removal are researched. The performed theoretical studies and numerical calculations made it possible to carry out practical tests and develop conditions under which the physical effect of laser energy causes minimal damage to the alloys and composites of the sample, as well as to assess the effect of the laser on the properties of materials used in the aerospace industry. The obtained results are reflected in the technology of laser selective removal of paint coatings from metal and composite skin of aircraft gliders.

Abstract: Ion-plasma modification of polymers has many potential applications, in particular, in the development of biomedical products. Treatment of soft polymers can easily damage the surface; low-energy plasma and subsequent investigation of the structural and mechanical properties of the surface are required. Polyurethane is a widely used block copolymer. Subplantation of carbon ions heterogeneously changes the structural and mechanical properties of the surface (relief, stiffness, thickness of the modified coating), forming a graphene-like nanolayer. Uniaxial deformation of the treated materials in some cases leads to the damage of the surface (local nanocracks, folds). Materials have increased hydrophobicity, good deformability (valid for certain treatment regimes) and can find application in design of products with improved biomedical properties.

Abstract: Currently, hard alloys are common tool materials; they are widely used in the tool manufacturing industry. Due to the presence of refractory carbides in its structure, hard-alloy tools feature a high hardness of 80 to 92 HRA (73 to 76 HRC); a high heat resistance (from 800 °С to 1,000 °С); therefore, they can be used at speeds that are several times higher than cutting speeds of high-speed steel grades. Hard alloys are used in the form of plates that are either mechanically fixed on or soldered to tool holders. The main operational parameters, that determine the hard-alloy tool operation mode, are hardness, wear resistance, and bending strength. The operational parameters of alloy are highly dependent on its structure, phase composition, lattice block sizes, and micro-stress values [1-20]. The main methods to enhance physical and mechanical properties of hard-alloy plates are improvement of manufacturing technology, including production of fine-grained alloys and microalloying, as well as applying composite coating by vacuum deposition, which allows to increase the tool resistance 1.5 to 2 times.

Abstract: The present study describes the impact of cutting speed and various lubricant-cooling process agents on the temperature of alloy turning. The research was conducted for NiCr20TiAl and N07750 nickel alloys with the help of HG30 and HS123 carbide-tipped cutting tools. New lubricant-cooling process agents with nanodispersed diamond graphite additives are studied. The optimal composition of the diamond graphite additives is revealed when cutting these alloys. It is demonstrated on the basis of tests the positive effect of diamond graphite agents on the quantitative changes in measured cutting temperatures. In doing so, the cutting speed and the lubricant-cooling agents applied to the cutting zone have little impact on the nature of temperature patterns.

Abstract: The article deals with the construction of an intensive process of grinding materials using a precast textured wheel and a device for the centrifugal giving of lubricating and cooling liquid (LCL) directly to the local contact zones of the cutting and pressing abrasive grains with the processed material. The design of the tool and an effective method of coolant giving to the cutting zone are described, which provide the required roughness of the treated surface and eliminate structural changes in the surface layer under intensive grinding conditions. An increase in the rate of heat removal from the grinding zone is achieved by using a textured tool design, a device for centrifugal giving of coolant and accelerating the liquid to approximately the cutting speed. A method for constructing an intensive grinding process with a precast textured tool has been developed, the implementation of which can significantly increase the processing efficiency. The results of the research are recommended for grinding steels, cast iron and other metals and alloys that are prone to the formation of cauterization, tensile residual stresses and other thermal defects that occur under the influence of high temperature in the grinding zone.

Abstract: The paper shows the applicability of expandable graphite METOPAC EG 350-50 (80) in a rigid PU foam system as a substance that reduces the flammability (flame retardant) and improves the usability. The studies of the physical mechanical and thermal properties of PU foam with a higher graphite content revealed a higher normal sound absorption coefficient; insignificant influence on the thermal conductivity; a higher decomposition onset temperature; more difficult ignition. PU foam sample with a ratio of 15 graphite weight fractions to 100 polyol weight fractions has the highest physical mechanical and thermal properties, and, as compared to the starting PU foam, it features an increase in normal sound absorption coefficient by an average of 3 times; a decrease in the thermal conductivity by 8 %; an increase in the decomposition onset temperature by 6.7 °С. Therefore, the modification of PU foam with expandable graphite makes it possible not only to develop hardly combustible polyurethanes but also to improve its physical mechanical and thermal properties.