Production Of Hard Alloys Research Articles

Manufacturing of die blanks from hard alloy granulated mixture and influence of chemical composition of the mixture on technological properties of hard alloy die blanks

The technology of manufacturing dies from a hard alloy granulated mixture includes the following operations: preparation of raw materials, forming of blanks, and subsequent sintering. The preparation of hard alloy mixtures consisting of carbide powders and binder metals is one of the main operations in the production of hard alloys. The properties of the resulting alloys largely depend on the conditions of performing this operation. All operations are interconnected, and any change in technological parameters can lead to a change in the formation of the final material structure and, consequently, its properties. This article discusses the technology of manufacturing and the production process of die blanks from a hard alloy granulated mixture. The results of laboratory studies of the hard alloy mixture, the manufacture, and production tests of die blanks are described.

Synthesis of non-stoichiometric carbides and carbohydrides of Ti and Ti-Nb using self-propagating high-temperature synthesis technique

Non-stoichiometric monocarbides are of great interest because they can be used as additives at production of hard alloys. Interestingly, the non-stoichiometric carbides of IV group metals provided with a wide range of homogeneity interact with hydrogen and form ternary compounds, carbohydrides. These compounds attract the researches as the bases for creating new hydrogen containing materials resistant at temperatures above those for known binary hydrides of transition metals. They are promising as materials for biological protection in nuclear energy. In the present work the single-phase non-stoichiometric face-centered cubic (FCC) carbides and hexagonal close packed (HCP) and FCC carbohydrides based on Ti and Ti-Nb were synthesized using Self-propagating High-temperature Synthesis (SHS) method. These syntheses were implemented in one technological stage. The high hydrogen content in the synthesized non-stoichiometric carbohydrides promoted their dispersion down to particle sizes of < 5 µm and even smaller, to the nanoscale crystallite sizes of < 50 nm. The mechanism of formation of non-stoichiometric carbides and carbohydrides in SHS was discussed. Significant advantages of a highly efficient non-energy-intensive SHS method for the synthesis of non-stoichiometric titanium and titanium-niobium carbides and carbohydrides can be of commercial and industry interest.

Composition, structure and properties of hard alloy products from electroerosive powders obtained from T5K10 hard alloy waste in kerosene

The paper implements scientific and applied principles of coupling the technology of obtaining new powder materials from waste of hard alloys of the T5K10 brand by electroerosive dispersion and the technology of compacting them by SPS synthesis. The aim of the work was to study the composition, structure and properties of carbide products made from powders obtained by electrodispersing T5K10 alloy waste in kerosene. Electrodispersion of T5K10 alloy waste was carried out in lighting kerosene on a patented installation. The consolidation of the obtained powder was carried out by the spark plasma sintering (SPS) method using the spark plasma sintering system SPS 25-10. The choice of powders obtained by electroerosive dispersion of the T5K10 hard alloy waste was justified by its cost and properties. The resource of tungsten-titanium-cobalt hard alloys from T5K10 electroerosion powders is determined not only by the properties of the feedstock, but also by the technology of their production (SPS synthesis). Based on the conducted experimental studies, it can be concluded that the use of the spark plasma sintering method to produce products from powder obtained by electroerosive dispersion of the T5K10 alloy will ensure high performance of products (cutting tools) due to the uniformity of the surface, favorable structure and low porosity of the product. It is noted that hard alloys made of electroerosion dispersed T5K10 alloy particles obtained by spark plasma sintering under conditions of rapid heating and short working cycle duration have higher physico-mechanical properties compared to industrial alloys from which the initial powder particles were obtained by suppressing grain growth and obtaining an equilibrium state with submicron and nanoscale grain. This study was funded by the Russian Science Foundation,&nbsp;grant No. 22-29-00123, https://rscf.ru/project/22-29-00123/.

Mathematical modeling of power consumption based on rank analysis

In the article, based on the application of the rank analysis of the technocenosis, mathematical modeling of electricity consumption by consumers for the production of hard alloys is carried out. Two methodological levels of research in the field of energy-saving and power consumption are presented. At the same time, it was found that rank analysis allows you to streamline information, effectively predict power consumption by individual objects to identify dynamics, and visually represent objects with abnormal power consumption. The analysis of the results obtained confirms the efficiency of using the H-distribution for obtaining mathematical models of power consumption of Noah and Pointer castes in the production of hard alloys. For the first time, the regularity of changes in electricity consumption by technological equipment was established, which is described by an adequate mathematical model in the form of a damped harmonic function. The resulting model is recommended for use in an automated dispatching control system for electricity consumption for the purpose of short-term forecasting of electricity consumption.

The Role of Binding Phase in Hard Alloys (Analytical Review)

A review of articles on the influence of the composition and structure of the binding phase on the properties of hard alloys is given. The role of the binding phase influencing the properties of hard alloys on the basis of data of domestic and foreign researchers is emphasized. The existing and new data on testing of the elements of periodic system as a binding phase which impacts the microstructure and properties of a hard alloy are presented. The existing and new proposals on replacing of the main element (cobalt) with iron, nickel, rhenium, molybdenum, chromium, etc., are considered in order to obtain higher properties and lower the price of the alloy. It is shown that obtaining the best operational properties in each particular case of application of the alloy requires an optimal combination of grain size and cobalt content. Various hard-alloy products are indicated for different areas of application. Techniques of reinforcement of the binding of hard alloys by means of introduction of various types of reinforcers are considered. Their influence on average grain size and properties of hard alloy is shown by examples of various grain growth inhibitors. The ways of further development of submicron, ultrathin, and nanophase alloys with a nanostructured binder reinforced with nanoparticles are presented. The way of further development of hard alloys is shown by example of alloy WC–50% Со with additions. The properties of replacing the cobalt binder with nickel alloyed with small additives are indicated: Мо, W, TiC, HfC, VC, NbC, TaC, Cr3C2.

Analysis of non-sinusoidal voltage at metallurgical enterprises

The article presents the results of the study of non-sinusoidal voltage in the power supply system of non-ferrous metallurgy enterprises. The non-sinus voltage coefficients are calculated for the operation of valve inverters and welding machines. The range analysis of the noah caste of higher harmonic components by voltage was carried out and it was established that the values of the correlation coefficients between the non-sinusoidal coefficients of voltage and the fraction of noah and pointer castes of electricity consumers for the production of hard alloys are equal to: 0.56 and 0.37, which makes it possible to limit the range of priority tasks for calculating the required filter-compensating devices. It is necessary to conduct further studies of higher harmonics in the system of power supply of industrial enterprises and the development of methods for calculating and optimal distributing filter-compensating devices in enterprises.

Data measurement system for non-destructive quality testing of hard alloys

Introduction. It is known that the quality of products from sintered hardmetals, if the fabrication technique is not violated, is determined by the phase composition and an average grain size of the carbide phase. However, hard alloys have a disadvantage inherent in all products of powder metallurgy - the inhomogeneity of the structure and the corresponding variation of properties. Traditional methods of monitoring the structure and phase composition according to the results of selective destructive tests prevent from receiving quality data under the production conditions and do not guarantee the identity of the properties of all batch products under study. The major method of non-destructive quality control of hard alloys is coercimetry, but domestic coercimeters are currently not produced. In this regard, the work objective is to create a domestic data measurement system for non-destructive quality testing of hard alloys and an assessment of the reliability of the results obtained with its help. Materials and Methods. Cylindrical and spherangular rods with the diameter of 4 to 10 mm, made of alloys of VK8 and VK10HOM grades, were used in the work. The method of comparison with a certified product was used to determine the coercitive force in the data measuring system. Research Results. The coercive force of two batches of products from hard alloys of VK10HOM and VK8 grades was measured using the developed data measuring system and KOERZIMAT 1.097 HcJ coersimeter. Discussion and Conclusions. The experimental studies show that the values of the coercitive force of the samples obtained on different equipment have approximately the same level. The inhomogeneity of the structure characteristic of sintered hardmetals being a fabrication technique effect is confirmed. Providing that the relative error of measuring the coercitive force for each sample should be within ± 6%, the results obtained can be considered satisfactory. It is shown that the measurement algorithm proposed and implemented in the data measurement system through comparing the characteristics of the tested and certified samples with the known coercitive force, allows the manufacturer of hard alloy products to expand the sample of inspected products up to 100%, and to significantly reduce the costs for non-destructive testing of products.

ICP-AES Analysis of Secondary Tungsten-Containing Raw Materials for Production of Hard Alloys

A method for ICP-AES determination of Ti, V, Cr, Fe, Co, Ni, Cu, Zn, and Ta in recycled cemented tungsten carbide is developed including preliminary microwave sample decomposition in a steam pressure vessel (autoclave). We have specified the composition of the reaction mixture for sample dissolution and optimized the parameters of microwave heating in the autoclave. Correctness of the results is proved by the method of sample weight variation and spike tests. The results of analysis are compared with the data obtained by standardless method of X-ray fluorescence spectrometry. The technique is characterized by good reproducibility and allows significant reduction of the analysis time owing to the combination of the multielement method of ICP-AES and microwave sample preparation.

Application of zirconium carbide: assessment, determination of dominant trends and prospects

The analysis and systematization of information on the application of zirconium carbide in modern technology: in the production of hard alloys and products from them, in technologies of anti-emission coatings, surface modification of powder materials. Prospective directions are indicated: a component in composite materials technologies, a modifying phase of galvanic metal matrix composite coatings, a functional component of wettable coatings for cathodes of alumina reduction cells.

Occurrence and Ways of Development of Manufacture of Domestic Hard Alloy Products

This article provides an overview of the stages of occurrence and development of the manufacturing of domestic hard alloys. It describes the contribution of domestic scientists to the development of various brands of hard alloys and establishment of their production. It shows the outstanding role of G.A. Meerson in the development of the hard-metal industry.

Development of structural diagram of automated dispatch control system for power consumption at non-ferrous metallurgy enterprises

The structural scheme of the automated control system of power consumption at the industrial enterprise is developed in the article. At the non-ferrous metallurgy enterprise, an energy inspection and a rank analysis of the electrical energy consumption of the main processing equipment were carried out. It is established that the enterprises of non-ferrous metallurgy are a complex process system consisting of a set of thousands of jointly functioning technological facilities. For the most effective estimation of power consumption of enterprises, it is reasonable to use the automated system of dispatching control of power consumption (ASDCPC). The paper presents the results of the development of the ASDCPC structural diagram that allows one to perform on-line control and management of the energy and process parameters of the main production units and the enterprise as a whole. As a result of the introduction of ASDCPC at the non-ferrous metallurgy enterprise, the consumed active power was reduced during the peak hours of the load by 20%, the specific electricity consumption - by 14%, the cost of the energy component in the cost of production of hard alloys - by 3%.

CURRENT STATE OF THE SCIENTIFIC PROBLEM OF WC–Co HARD ALLOYS SURFACE HARDENING (REVIEW)

The article presents the review of Russian and foreign researches on surface hardening of WC – Co hard alloys aiming at increasing their wear-resistance. There is a great reserve of increasing wear-resistance and operational durability of hard-alloy products in application of surface methods of hardening using different coatings and coating with basic structural components of up to 100 nanometers. The most widely spread coatings on WC – Co hard alloys are coatings made from TiC, TiN providing high energy lattice ties, high flowing temperature and hardness. Use of TiC, TiN as surface layers on hard-alloy tools results in reduction of friction coefficient in pair with steel in 1.5 – 2.0 times, but use of TiN + ZrN ionic-plasma coatings reduces friction coefficient in 5.9 times in comparison with the initial condition. Today multilayer coatings are very popular. The most widely spread are coatings of TiN + TiC and Al2 O3 + TiC. Their surface wear is directly proportional to the coating thickness. Combined multilayer coatings described above are not the final solution to the problem of increasing wear resistance of hard alloys. The research projects are carried out in our country that are based on theoretical possibilities for obtaining strength of the hard alloy gradually from viscous and high-strength core to wear-resistant surface. The FSUE VNIITS has developed a method for obtaining alloys with variable content of cobalt along the plate thickness. Due to this, it is possible to vary composition of alloys along the thickness of sample, from VK20 to VK2, as a result working part of plate has wear resistance equal to VK2 alloy, and the base enduressignificant bending stresses. Recently different cutting tools with diamond coatings on hard alloys have been used in Russia and all over the world. To increase the service life of hard-alloy plates of VK group, methods of hardening using concentrated energy flows are used. Among them there are hard alloys’surfaces treatment by γ-quanta, ion beams, laser beams; electro-explosive alloying, electro-erosion hardening by alloying etc.

A study on the production of titanium carbide nano-powder in the nanostate and its properties

The plasma synthesis of titanium carbide nano-powder in the conditions close to industrial was studied. Titanium carbide TiC is a wear- and corrosion-resistant, hard, chemically inert material, demanded in various fields for the production of hard alloys, metal- ceramic tools, heat-resistant products, protective metal coatings. New perspectives for application titanium carbide in the nanostate can be found in the field of alloys modification with different composition and destination.

Electroerosion micro- and nanopowders for the production of hard alloys

The shape and the surface morphology of the powder particles fabricated by the electroerosion dispersion of tungsten-containing wastes in illuminating oil are studied. The hard alloy fabricated from these powder particles is analyzed by electron-probe microanalysis. The powder synthesized by the electroerosion dispersion of the wastes of sintered hard alloys is found to consist of particles of a spherical or elliptical shape, an irregular shape (conglomerates), and a fragment shape. It is shown that W, Ti, and Co are the main elements in the hard alloy fabricated from the powder synthesized by electroerosion dispersion in illuminating oil.

Formation of the gradient structure in sintered hard alloys (review)

Papers on the formation of gradient structures in sintered hard alloys have been reviewed. It has been shown that at present there are three directions in the development of gradient structures. The first of them involves the application of surface layers to a hard alloy product by depositing carbides, nitrides, oxides of various chemical elements in different combinations. The second involves the formation of the layer structure in a product during machining or as a result of the action of high-energy beams of electrons and ions, as well as by a laser treatment. The third direction involves the development of technologies of the creation of gradient structures in the bulk of sintered hard alloy products. The work in all three directions is aimed at adapting hard alloy product to its working conditions and thus increasing its efficiency.

Structural and statistical model of a hard alloy with damages

An approach to a construction of the micromechanical theory of the hard alloy strength has been proposed, which is based on a combination of the structured modeling and statistical theory of extreme values. Computational experiments using the structural model have been performed with the aim to construct a continual theory of the accumulation of damages in a hard alloy and revise parameters that form a part of criteria for strength and life of hard alloy products. The introduced micro damage parameter has been related to the Pisarenko-Lebedev criterion for static strength. The possibility to improve the proposed theory and its application in practical calculations of strength and durability of hard alloy products has been discussed.

Spark erosion processing of hard tungsten-cobalt alloy in water and subsequent carbonization

The paper examines the advanced method of spark erosion for recycling hard-alloy scrap. It is shown that spark discharge over hard alloy in water leads to the decarburization of the initial WC phase in the surface layer and of the powder formed. After carburization, the powder can be used for the production of hard alloys. The structure and mechanical characteristics of the hard alloy made of the powder are studied.

Longevity of tungsten-cobalt alloys under load in a corrosive environment

We studied the influence of the chemical composition of the WC-Co cermet system on the operating characteristics of hard-alloy tips of drill bits manufactured from it. We established that the cyclic contact strength of tips in air at room temperature and the threshold range of the stress intensity factor in the tip material increase with the cobalt content. Using the results of tests of the materials for cyclic crack resistance, as well as of cavitation-erosion and electrochemical tests in 3% NaCl aqueous solutions, we ascertained that the optimum corrosion and mechanical characteristics correspond to the composition containing 8 mass% Co. We noticed a significant contribution of the anodic dissolution of the Co-phase and its hydrogen embrittlement in the process of corrosive-mechanical damage of hard alloys. We discovered a satisfactory correlation between the parameters of cyclic contact strength, threshold range of the stress intensity factor, and steady-state rate of cavitation-erosion failure of WC-Co hard alloys. This fact demonstrates the possibility to use these parameters as reliable and interchangeable criteria of the operational reliability of hard-alloy products.

Phase equilibria in the Cr-Ni-C system and their use for developing physicochemical principles for design of hard alloys based on chromium carbide

The Cr—Ni—C phase diagram at the melting point was plotted by a combination of procedures (metallography, x-ray, microprobe, differential thermal analysis, Pirani—Alterthum method, etc.). A general feature of this system is the existence of equilibria between the nickel-based phase and all the other phases. The temperature of the quasibinary (Ni)+(Cr7C3) eutectic was determined to be 1324±6°C. Based on both the phase diagram of the Cr—Ni—C system and the bending strength and Rockwell hardness of the alloys, the optimal composition of the initial carbide ingredient for production of hard alloys based on Cr3C2 with nickel—phosphorus binder was estimated as 13.0–13.3 at.%, substoichiometric with respect to Cr3C2.

Improving the properties of hard alloy products by machining

1. The bending strength in plates made by using machining is 25% higher than that of plates pressed into a complete section. 2. An important role in reducing the static bending strength of a concentrated load in products in relation to the method of formation is played by the zone adjacent to the bevel. 3. Making the articles by machining enables us to obtain a better surface finish on the cutting face.