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

This study investigated the effect of cold plastic deformation at Bridgman anvil chamber temperature on the hardness and wear resistance of X160CrMoV12 steel using hardness testing, X-ray diffraction (XRD), abrasive grinding wear (AEMW) testing, optical examination, and scanning electron microscopy (SEM). Three batches of samples were prepared for the experiment: I – hardened, II – hardened and then tempered at 600°C for 1.5 hours, III – hardened and then plastically deformed. The samples were hardened at three temperatures: 1100, 1150, and 1200 °C. The highest amount of retained austenite, reaching 69.02%, was observed when hardening at 1200°C, while at lower temperatures, 17.36% and 38.14% were formed, respectively. After hardening (batch II), the amount of retained austenite decreased proportionally by approximately 7 times for each hardening temperature. The effect of plastic deformation (batch III) is observed by analysing the hardness of samples from the surface to the depth, reaching an average hardening depth of 0.08 mm. To check how well it holds up to wear, the surfaces of three test batches were tested using an abrasive grinding test with a load of 5N. Hardened and plastically deformed specimens showed greater resistance to abrasion than hardened and tempered specimens. The results confirmed that the optimal hardening temperature for achieving maximum wear resistance of this steel is 1100°C.

The effect of individual additions of Ti and B into high chromium white cast irons (HCWCIs) on the structure, corrosion and selected mechanical properties was investigated. Two different heat treatments were applied, high-temperature treatment at 960 oC/1h, and subcritical treatment at 550 oC/4 h. The microstructure was investigated by OM and SEM; compositions of matrix and carbides were analyzed by EDS. Mechanical behavior of HCWCIs was analyzed by measuring hardness, toughness, abrasive/wear resistance and resistance to repeated impacts. Corrosion behavior was evaluated electrochemically, by linear and Tafel polarization methods in 0,1M NaCl solution. The properties of the modified HCWCIs were compared with the properties of the base unmodified HCWCI alloy (ASTM A532-IIE).

Studies of the tip of a road milling cutter made of tungsten-cobalt alloy have been carried out. It is established that one of the factors influencing the wear resistance of the tip is the porosity of the sintered hard alloy. Laser treatment of the surface of the cutter tip was performed. It has been found that under certain laser radiation conditions, the number of pores in the cutter decreases.

X-ray diffraction analysis of the Fe-35%FKh800-(0.38-2.2%)TiB2 system samples showed that a multiphase composition of materials is formed during the sintering process. The basis of the sintered composite is the ferrite α-Fe phase, which is a metallic ironchromium matrix, with γ-Fe, complex iron-chromium carbide (Fe,Cr)7C3, and carboboride phases in small amounts: borocementite – Fe3(B0.7,C0.3) with a rhombohedral lattice and carboboride Fe23(C,B)6 with a cubic lattice and a number of carbides (Cr7C3, Cr3C2). The research established the non-monotonic nature of the effect of the TiB2 additive content on the lattice parameters of the ferrite α-Fe and austenitic γ-Fe phases, as well as on the change in the intensity of the 111 line of the austenitic phase. According to the phase composition data and studies of the fine structure (substructure) of the sintered samples of the Fe-FKh800-TiB2 system materials, it can be noted that the components of the TiB2 alloying additive take an active part in the formation of the phase composition, as well as in the process of alloying the matrix phase, which is reflected in the numerical values of the substructure parameters.

This work presents a brief overview of the essence, principles and technological features of reactive electrospark processing (RESP), based on a simple, economical and ecological method – electrospark deposition (ESD), which avoids many of the disadvantages inherent in other existing methods. This treatment can optimize the physicochemical properties of the substrate surface and improve the structure, hardness and wear resistance. The application of RESP technology in surface modification of titanium alloys is considered. Research results, including those of the authors of this work, are presented, which demonstrate the possibilities of RESP for reducing
roughness and surface defects and for the synthesis of new phases and ultrafine structures that are not present in the electrode and substrate. The effect of RESP technology on the wear resistance of titanium and titanium alloys is shown. The main dependences of the quality and properties of the treated surfaces on the process parameters are identified, and ways to form reaction phases, to avoid and remove surface defects and to obtain “in-situ” new intermetallic and wear-resistant compounds are presented. The possibilities and prospects for the use of RESP to improve the surface characteristics and properties of titanium and its alloys are indicated.

The article presents the results of investigations of tribotechnical properties of powder composite materials based on the ironhigh-carbon (ФХ800) ferrochrome system during dry friction with ШХ15 steel at various loads of 30, 60, and 100 N. It was found that an increase of the load from 30 to 100 N leads to an increase in the coefficient of friction from 0,45 to 0,5 (for 25% ФХ800) and from 0,40 to 0,46 (for 40% ФХ800). At the same time, the mass wear of samples made of powder materials decreases with an increase in ФХ800 content from 25 to 40 (wt. %) and with growth of the load from 30 to 100 N, respectively, from 3,5 – 8,0 to 0,75 – 1,6 mg/km., which provides wear resistance improvement (km/mm) by 2,8 – 2,2 times. X-ray phase full profile analysis using the Rietveld method established that there are 2 phases: metallic α-Fe (79,68%) and carbide Me7C3 (20,32%) in the composite Fe – 25%ФХ800 and 3 phases: α-Fe (69,5%), γ-Fe (3,96%) and carbide Me7C3 (26,57%) in the Fe – 40% ФХ800 composite. Topographic studies of 2D profiles of worn surfaces of composites after friction under different loads were conducted. The results of optical profilometry show that the main mechanism of destruction of the powder composite surface during dry friction with ШХ15 steel is adhesive wear (seizing) of the contacting surfaces.

This work discusses the properties of 3D titanium alloys with wear-resistant coatings of hard alloy electrodes based on WC-TiB2-B4C and solder mass of Co-Ni-Cr-B-Fe-Si-C, produced by reaction electrospark processing (RESP) at positive and negative polarity. Through profilometric, metallographic, XRD, SEM, EDS and tribological methods, the complex influence of polarity and pulse energy on the topography, composition, properties, and wear characteristics of the coated surfaces was investigated. The differences in the coatings obtained with the two polarities were identified. Coatings with similar roughness and thickness were obtained, which can be changed by changing the modes for RESP within the limits Ra =2.5÷5μm, δ= 8÷40μm, with microhardness 8 to 14 GPa and 2-4 times higher wear resistance than that of the substrate. At RESP with negative polarity and pulse energy up to 0.04 J, the coatings have comparable characteristics and properties to those at positive polarity, but lower roughness, finer structure and lower coefficient of friction. These coatings can be successfully used to reduce roughness and surface defects and improve the wear resistance of 3D titanium alloys. The pulse energy and polarity of RESР, producing coatings with minimum roughness and maximum wear resistance, have been determined.

In this work the possibilities of reducing the roughness and defects of surfaces obtained by 3D printing with selective laser melting (SLM), via reactive electrospark surface modification (ESD) with low-melting AlSi alloys has been shown. The influence of the energy parameters of the ESD process on the roughness, microstructure, microhardness and performance characteristics of the coatings has been studied. Surfaces with new phases and ultrafine crystal-amorphous structure with particle sizes from micro to nano level, with new relief, with thickness up to 15 μm and microhardness up to 11 GPa were obtained, as the initial SLM roughness from Ra = 8-11μm is reduced to Ra=3-5 μm. Possibilities for control of the characteristics of the coatings and purposeful synthesis of new phases by changing the parameters of the spark discharge have been established. The parameters of the ESD process, which provide simultaneous reduction of SLM surface roughness, removal and erasure of the defects and targeted reactive synthesis of new phases with high performance properties and wear resistance, are defined and optimized.

The research of the technology of obtaining new copper-ferrochrome composite material has been done. The results of its structure and properties analysis are presented. The material structure consists of the copper base, non-dissolved coarse inclusions of ferrochrome, diffused zones, forming around these inclusions and phases, having formed in the place of completely dissolved inclusions of ferrochrome fine particles. The material has good mechanical properties and a high wear resistance due to the formed solid solutions of the carbides in the copper.

Analysis of the structural state and phase composition of surface metal layers after combined treatment of steel which includes preliminary surface plastic deformation of the workpiece, electrospark doping with use of rotating disk electrode 2 mm thick, made of WCCo hard alloy and subsequent surface ball smooth rolling, has been performed. It was shown that the use of combined treatment provides a gradient-layered structure with low surface roughness. Phase composition of the obtained layer consist of ferritic α-Fe phase and a number of carbide phases formed during the interaction of the electrode material with steel: F3W3C, WC and W2C semi-carbide. Wear resistance of the material after treatment exceeds similar properties of the original carbon steel up to 4 times.

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.

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.