Investigation of Electromagnetic Properties of Tool Hard Alloys under the Influence of High Temperatures

The article shows the developed installation for determination of temperature of maximum operability of replaceable cutting hard-alloy plates on the basis of study of change of electromagnetic properties. The method of research is given. Tests of images were carried out to time of heating of the replaceable cutting plates from solid B35 alloy. The heating temperature interval was selected according to the temperature mode of the process of cutting difficult materials. Heating was carried out to 1000˚ C. The results of the study were obtained to determine the temperature of maximum operability of replaceable cutting hard alloy plates based on the study of the change in electromagnetic properties for alloy В35 amounted to 460-730 ° С.

Impact of Magnetic-Pulse and Chemical-Thermal Treatment on Alloyed Steels’ Surface Layer

The relevant problem is searching for up-to-date methods to improve tools and machine parts’ performance due to the hardening of surface layers. This article shows that, after the magnetic-pulse treatment of bearing steel Cr15, its surface microhardness was increased by 40–50% compared to baseline. In this case, the depth of the hardened layer was 0.08–0.1 mm. The magnetic-pulse processing of hard alloys reduces the coefficient of microhardness variation from 0.13 to 0.06. A decrease in the coefficient of variation of wear resistance from 0.48 to 0.27 indicates the increased stability of physical and mechanical properties. The nitriding of alloy steels was accelerated 10-fold that of traditional gas upon receipt of the hardened layer depth of 0.3–0.5 mm. As a result, the surface hardness was increased to 12.7 GPa. Boriding in the nano-dispersed powder was accelerated 2–3-fold compared to existing technologies while ensuring surface hardness up to 21–23 GPa with a boride layer thickness of up to 0.073 mm. Experimental data showed that the cutting tool equipped with inserts from WC92Co8 and WC79TiC15 has a resistance relative to the untreated WC92Co8 higher by 183% and WC85TiC6Co9—than 200%. Depending on alloy steel, nitriding allowed us to raise wear resistance by 120–177%, boriding—by 180–340%, and magneto-pulse treatment—by more than 183–200%.

RESEARCH OF THE CUTTING MECHANISM AT ELECTRICAL DISCHARGE GRINDING

The paper presents the results of a study of the cutting mechanism during electrical discharge grinding of hard alloys. The cutting mechanism during electrical discharge grinding was studied using mathematical modeling. By means of geometric modeling, a method of grinding cup wear was developed. The functional dependence of the diamonds use factor in the Kw wheel on the technological parameters of processing, wear and tool characteristics were determined. Analysis of the results of the study shows that an increase in efficiency at electrical discharge grinding can be achieved by reducing the wear of S, and by corresponding variation in the concentration of diamonds and technological modes of processing.

Synthesis of titanium carbide and titanium diboride for metal processing and ceramics production

Introduction. Titanium carbide and diboride are characterized by high values of hardness, chemical inertness and for this reason are widely used in modern technology. This paper provides information on the synthesis of titanium carbide and diboride by carbothermal and carbide-boron methods, respectively, on the use of titanium carbide as an abrasive and in the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, as well as titanium diboride in the production of cutting tools and ceramics based on boron carbide The aim of this work is to study the processes of synthesis of highly dispersed powders of titanium carbide and diboride, which are promising for the manufacture of cutting tools, wear-resistant coatings, abrasives and ceramics. Research methods. Titanium oxide TiO2, nanofibrous carbon (NFC), and highly dispersed boron carbide were used as reagents for the synthesis of titanium carbide and diboride. Experiments to obtain titanium carbide were carried out in a resistance furnace, and titanium diboride in an induction furnace. X-ray studies of the phase composition of titanium carbide and diboride samples were carried out on an ARL X-TRA diffractometer (Thermo Electron SA). The determination of the content of titanium and impurities in the samples of titanium carbide and diboride was carried out by the X-ray spectral fluorescence method on an ARL-Advant'x analyzer. The total carbon content in the titanium carbide samples was determined on an S-144 device from LECO. The content of boron and other elements for titanium diboride samples was determined by inductively coupled plasma atomic emission spectrometry (ICP AES) on an IRIS Advantage spectrometer (Thermo Jarrell Ash Corporation). The surface morphology and particle sizes of the samples were studied using a Carl Zeiss Sigma scanning electron microscope (Carl Zeiss). The determination of the particle/aggregate size distribution was performed on a MicroSizer 201 laser analyzer (BA Instruments). Results. The paper proposes technological processes for obtaining highly dispersed powders of titanium carbide and diboride. The optimum synthesis temperature for titanium carbide is 2,000…2,100 oC, and for titanium diboride 1,600…1,700 oC. The content of the basic substance is at the level of 97.5…98.0 wt. %. Discussion. A possible mechanism for the formation of titanium carbide and diboride is proposed, which consists in the transfer of vapors of titanium oxides to the surface of solid carbon (synthesis of titanium carbide) and vapors of boron and titanium oxides to the surface of solid carbon (synthesis of titanium diboride). Due to the high purity and dispersion values, the resulting titanium carbide powder can be used as an abrasive material and for the manufacture of tungsten-free hard alloys, carbide steels, wear-resistant coatings, and titanium diboride powder can be used for the preparation of cutting tools and ceramics based on boron carbide.

TECHNOLOGY OF DEPOSITION OF COATINGS FROM HARD ALLOYS ON THE WORKING SURFACES OF FRICTION UNITS

A technology has been developed for applying explosively to the surface of centrifugal pump parts for pumping overheated distillate under NPP conditions of hard alloy coatings of the CrC-Ti system, which ensures high hardness of the coatings and the strength of their connection with the surface to be coated, and the best tribotechnical materials in comparison with existing materials friction characteristics against siliconized graphite in water.

Impact of orbiting electrode motion on the accuracy of electrical discharge machining

The present study is designed to study processes occurring during the electrical discharge machining (EDM) of tool steels, the influence of orbiting electrode motion on its accuracy, as well as to justify the application of individual orbiting trajectories and implement these data into production. To that end, a trajectory program was written in machine codes for a Mitsubishi EA-28 die-sinking electrical discharge machine using the CIMCO EDIT software package. Also, a prototype punch and ejector of the blanking die were produced and measured. The standard modes of Mitsubishi EA-28 were used to carry out machining in Blasospark GT 250 dielectric fluid to a roughness of Ra 0.6 in 9 passes. The experiments revealed the influence of electrode geometry on the machining of sharp corners, i.e., the formation of unwanted radii on the workpiece. However, this phenomenon is not observed when the corners are drilled with small diameter holes (0.4–0.6 mm). Depending on the machining process along the inner or outer trajectory, inverse electrode motion is also observed. The production part (punch of the blanking die) was machined using a new orbit adjusted to the geometry of the product. The part was found to be consistent with the requirements and the engineering drawing, thus allowing the assembled die to enter the main production. The results of the performed tests, as well as the study of domestic and foreign experience, were used to develop recommendations on the use of individual orbits in the EDM of tool steels, hard alloys, and other hard-to-machine conductive materials. The method of orbiting motion along a particular trajectory was implemented at Cheboksary Electrical Apparatus Plant (Cheboksary).

Mechanisms of structural-phase transformations during crystallization of solder melt under conditions of magnetic-dynamic influences for carbide tools

The processes of melt formation were studied by methods of optical and electron scanning microscopy. These processes occur during induction brazing of a hard alloy to a steel holder and contact interaction of low-melting (copper-zinc system alloy) and refractory (iron-nickel) components of the solders. It is shown that the effect of a thermal and magnetic-dynamic high-frequency electromagnetic field on the components of the composite solder is how a high-strength solder joint is formed. The structure is forming by disperse hardening mechanism. The research of the contact interaction process for low-melting and high-melting components of solders during the soldering process of the tool showed that the formation of solder in brazed seams occurs through a number of stages and this does not lead to the formation of microstructures that are characteristic of alloys based on copper-iron-phosphorus, copper-zinc-nickel and copper-zinc-iron. Thus, the use of composite solders can reduce the soldering temperature by 40-50 K and increase the concentration of alloying species in the solder and change its structure. These advantages of composite solders reduce the thermal impact on contact materials, increase the strength of the weld and allow you to control the thickness of the brazed weld, and this is important when soldering hard alloys of WC-TiC (TaC) systems. High initial dissolution rates of nickel particles in the copper-zinc melt and the solubility of copper, zinc in nickel lead to the formation in the melt of quasi-liquid particles of the nickel alloy. When the melt is cooled, particles other than the surrounding alloy composition are formed. They are morphologically related to the grain structure of the solder. The formed alloy (solder) has the structure of a composite material in which the metal particles are enriched in nickel, and have the role of a reinforcing element.