Metal-cutting Tools Research Articles

A Study of the Features of Coating Deposition on a Carbide Substrate Using Preliminary Etching with Glow-Discharge Plasma

The properties of coatings obtained using two surface preparation methods were compared: heating and etching by ion bombardment with plasma generation by arc evaporators and heating and etching by a glow discharge. A Ti-TiN-(Ti,Cr,Al)N coating was deposited. The use of a glow discharge provides better resistance of the coating to destruction during the scratch test and wear resistance of metal-cutting tools when turning steel. As the cutting speed increases, the advantage in wear resistance of the coating deposited using a glow discharge increases. During the process of heating and etching by ion bombardment with metal ions, a nanolayer rich in cobalt and tooling elements (iron, molybdenum) is formed in the area of the interface of the coating and the carbide substrate. When heated and etched by a glow discharge, such a layer does not form. When using both methods, there is identical diffusion of tungsten into the coating and diffusion of chromium and possibly titanium into the substrate. Thus, the glow-discharge heating and etching method can be effectively used in the process of PVD coating deposition.

PROSPECTS FOR THE USE OF COMBINED METAL-CUTTING TOOLS FOR THREADING

This article examines the use of combined metal-cutting tools for performing threading operations. The main purpose of the work is to analyze the effectiveness of using these tools in terms of improving accuracy, productivity and cost-effectiveness of processing. Combined tools show significant advantages over traditional methods, including reduced processing time, improved accuracy characteristics and reduced equipment maintenance costs. The design features and principles of operation of boring threaded cutters and threaded combs, as well as their impact on production processes and the quality of final products, are considered. Threading with the use of combined metal cutting tools allows you to integrate several technological operations in one cycle, which helps to increase efficiency and reduce basing errors. Experimental data confirm that the use of comb cutters contributes to a significant increase in processing accuracy and productivity, as well as reducing the time required to perform operations. Comparative analysis has shown that combined tools provide a higher quality of the thread being cut and an extended service life compared to traditional processing methods. Keywords: combined metalcutting tools, threading tools, boring threaded cutters, threaded combs, threading, productivity, processing quality.

Maximal productivity rate of threading machine operations

The quality of products in manufacturing engineering depends first of all on the machining processes. One of the crucial economic components of the production processes is the metal-cutting machining technologies that form the quality of manufactured objects. The physics of metal-cutting technologies is complex and cannot be described by one mathematical model because of different natures. Researchers derived an empirical formula of their tool life that describes the properties of the metal-cutting tools depending on many mechanical factors mentioned above. Engineers investigated and worked the metal-cutting regimes for manufacturing processes that comprise recommendations for the tool life. The components of the tool life are obtained by the practical tests at the research laboratories that give the approximated results. Practice shows the recommendations of the handbooks for metal-cutting regimes are not always optimal for manufacturing processes. The machine tools’ work in the manufacturing environment differs from the research laboratories. This work considers the analytical optimization of the cutting speed for the threading machine tool by the criterion of its maximal productivity rate.

Technological support for the durability of metal-cutting tools by the formation of wear-resistant coatings using energy-efficient methods

Technological support for the durability of metal-cutting tools by the formation of wear-resistant coatings using energy-efficient methods

УПРОЧНЕНИЕ МЕТАЛЛОРЕЖУЩЕГО ИНСТРУМЕНТА ЭЛЕКТРОИСКРОВОЙ ОБРАБОТКОЙ

Metal-cutting tools during the machining of parts by cutting experience high strength and thermal loads, causing wear of the cutting edges. Increasing the wear resistance of the cutting edges of a metal-cutting tool is an urgent task. (Research purpose) The research purpose is analyzing the causes of wear of end mills and drills and proposing the most rational method of hardening metal-cutting tools. (Materials and methods) End mills and drills were chosen as the object of research. The BIG-5 installation with the use of electrodes made of hard alloys VK8 and T15K6 was used to harden metal-cutting tools. It was pointed out that relatively mild electrical modes with pulse energy from 0.05 to 0.2 joules are used to harden drills and end mills, the thickness of the applied coating layer in such modes is 10-30 micrometers. (Results and discussion) It was noted that the performed analysis of the applied hardening methods confirmed the feasibility of using electric spark processing for these purposes. The optimal modes of electric spark processing were selected on the basis of previous studies. Comparative tests for wear resistance of samples from materials of end mills (P18) and drills (P6M5) were performed. It was shown that when using electrodes made of T15K6, the wear resistance of the samples increases by 1.85 times for P18 and by 8 times for P6M5. Comparative tests of hardened end mills and drills for wear resistance were carried out. The indicator was the number of processed parts. (Conclusions) The result of using the electric spark processing method to harden the cutting tool was an increase in the life of end mills by 3.8 times, drills by 2.25 times. The productivity of manufacturing parts has increased.

A wear testing method of straight blade tools for Nomex honeycomb composites machining

Ultrasonic vibration machining (UVM) with a straight blade tool (SBT) is currently an efficient process for part manufacturing of Nomex honeycomb composites (NHCs) in the aerospace industry. To solve the wear evaluation problem of SBT, this study focused on the failure characteristics of tool edge blunting, which was different from that of traditional metal-cutting tools. The edge radius measured by ultra-depth microscope and a dimensionless parameter Bluntness Coefficient (CB) obtained from fiber-cut sharpness test were applied to evaluate SBT wear. The fiber-cut sharpness test was realized by a two-stage model proposed based on fiber failure analysis and force-displacement curve, which were validated by experiments. A standardized testing device was established based on the model, and a relationship between edge radius and CB was obtained by testing quantitatively blunted SBTs. Machining experiments were carried out to obtain a correlation between tool performance and CB, and a failure standard of CB value for SBT was proposed. It was demonstrated that CB was an efficient indicator for SBT wear evaluation, and the sharpness testing by cutting fibers could characterize SBT wear with favorable accuracy and repeatability.

FEATURES OF VIBRATION DAMPERS APPLICATION IN THE DESIGN OF VIBRATION-RESISTANT METAL CUTTING TOOLS

Dry and viscous friction is used as a damper of oscillation energy in the construction of metal-cutting tools. A mathematical model of a two-mass oscillatory scheme of the insert of an assembled milling cutter was developed and studied, one of the masses of which models the clamped part of the insert - a press connection with dry friction, and the other - the cantilever part, which is subject to self-oscillations that are possible in the process of metal cutting. The influence of dry friction in the press joint of the insert on the amplitude of resonant oscillations of the cutter and the part was analyzed. The possibility of reducing the magnitude of the cutter's self-oscillations is demonstrated by selecting the most suitable parameters for the press connection of inserts with the body of the assembled milling cutter. The influence of internal viscous friction in materials with a high level of energy damping on the amplitude of self-oscillations of the cutter was evaluated and the possibility of their use in the design of a vibration-resistant metal-cutting tool was considered.

Assessment of microrelief of nanostructured surface of metal-cutting tools by image processing methods

Using replaceable multifaceted carbide inserts as an example, the results of studying the possibility of using image processing methods to assess the surface microrelief of a nanostructured metal-cutting tool are presented.

The influence of etching in a glow discharge plasma on the properties of wear-resistant coatings for metal-cutting tools

The influence of etching in a glow discharge plasma on the properties of wear-resistant coatings for metal-cutting tools

Tool for turning of workpieces ends made of difficult-to-cut steel 12Kh18N10Т

The need to process difficult-to-machine corrosion-resistant stainless steels of grade 12Kh18N10Т is growing sharply. While for external processing of workpieces made from such steels there are publications with recommendations on the choice of metal-cutting tools, there are no recommendations for the case of processing the ends of such workpieces. The article discusses issues related to the peculiarities of choosing a turning tool for machining the ends of workpieces made of steel 12Kh18N10Т.

Design of metal-cutting tool coatings at the atomic level

The research aims to lower tooling costs by reducing the time allotted to designing coatings on domestic cemented carbide metal-cutting tools by using the atomic force approach. The object of the study is coatings on cemented carbides of the tungsten carbide group such as titanium carbide (TiC), titanium nitride (TiN), and titanium (Ti) coatings or a nitride-based titanium, chromium and aluminum (Ti,Cr,Al)N composite coating. To select the most rational coatings, the article employed the method of calculating the functionals of interatomic systems using the density functional description of single atoms. The simplest measure to reduce the cost of designing metal-cutting instruments for manufacturing parts made of difficult-to-machine materials is to develop coatings for this tool type. The article considers various atomic arrangements in the coating material in relation to the WCo8 cemented carbide (VK8, tungsten carbide-cobalt alloy containing 8% cobalt). The calculated values of the interaction energy of the coating material atoms with one another and with the cemented carbide material ranged from 3.04 to 3.5 J/m2. Moreover, the research has established a correlation between the calculation results and the performance parameter of metal-cutting tools considering fracture toughness K1c (MPa ∙ √m). The main result of the study is that the employed computational method made it possible to determine the adhesion value for the atoms of the above-mentioned coating materials with tungsten carbide and cobalt atoms packed in different scale configurations. This enables the classification of coatings from the perspective of ensuring maximum performance properties of the tooling material. The present article assumes that the higher the adhesion value, the better the performance properties. The hypothesis has been confirmed experimentally as well as by the values of fracture toughness K1c. Thus, the most rational coating options have been selected for specified operating conditions of a metal-cutting tool, which permits reduction of tool design costs and makes it possible to predict the performance properties of tools at the design stage.

Sintered powder high-entropy target cathodes for wear-resistant coatings

Modern machine-building production equipped with high-performance mechatronic systems and numerically-controlled and adaptive control machines for blade cutting of heat-resistant chromium-nickel and titanium alloys requires increasing the operating properties of cutting tools working at high temperature-force loads in the contact zone, respectively with a significant stress-strain state of the cutting wedge. It is possible to solve the problem of increasing wear resistance and serviceability by developing and introducing new tooling material, as well as by applying wear-resistant coatings. The paper presents the results on development of technology for obtaining high-entropy target cathodes by spark plasma sintering with subsequent application of wear-resistant coatings on metal-cutting tools by both magnetron and ion-plasma methods. Samples of sintered high-entropy target cathodes of different compositions (more than fourteen) and at different modes of their sintering (depending on temperature in five modes) with their subsequent optimization and two standard sizes (20 and 80 mm) were obtained for further application of wear-resistant coatings on the magnetron unit. The authors carried out structural and phase analysis and studied physicomechanical properties of the obtained high-entropy target cathodes: density, hardness, electrical conductivity, emissivity. The possibility of obtaining high-entropy target cathodes by spark plasma sintering was confirmed experimentally, and the effect of sintering temperature on structure and properties of the sintered samples of high-entropy target cathodes was established. Dependence of physicomechanical and electrophysical parameters of target cathodes on technological modes of spark plasma sintering is shown.

Experimental Study of Improving the Durability of a Cup Cutter by Pre-Processing

This article presents the results of an experimental study on improving the durability of cup cutters through pre-processing. A review of existing methods of increasing the durability of metal-cutting tools is carried out. The conducted experiments and simulations confirmed the application of pre-processing to increase the durability of cup cutters and the hardening of the cutting part after pre-processing, which approves the formation of a secondary contact structure in the pre-processing process. Dependence for determining a period of the durability of cup cutters at various regimes of pre-processing is deduced.

Теоретическое исследование кривизны обработанной поверхности при косоугольном фрезеровании сборными фрезами

Introduction. The paper discusses the methods of processing large parts having curved convex surfaces with a rectilinear guide on multi-coordinate CNC machining centers using the touch method with a discrete motion of the tool feed along the profile of the part. It is shown that the main disadvantages of this method are lower productivity, which is due to the presence of discrete tool motions between cycles of its translation mode, where the value of discrete tool motion for a given processing accuracy depends on the curvature of the surface being processed. To improve processing performance, it is proposed to use prefabricated disc cutters equipped with replaceable polyhedral inserts (RPI) with rectilinear cutting edges. Its installation in the cutter body with non-zero angles of inclination of the main cutting edge, in combination with an additional rotation of the cutter, during processing, along the direction of the translational feed movement, allows you to obtain a concave surface and ensure a tighter fit of the producing surface of the tool and the machined surface of the part. The aim of the work is to reduce the error of approximation of the profile when it is processed using the touch method with discrete motion of prefabricated disc cutters along the profile and, consequently, to ensure workpiece the possibility of increasing the step of tool movement along the profile being formed to improve processing performance. Research methods: geometrical theory of designing metal-cutting tools. Results and discussion. The regularities established in the work made it possible to create a method for determining the angle of inclination of the main cutting edge of the RPI milling cutter and the angles of rotation of the milling cutter along the direction of translational feed movement during line-by-line processing of extended sections of parts with a curved profile on multi-coordinate CNC machines by turning the milling cutter to ensure the best fit of its producing surface to the surface being processed at the point of its contact, to reduce the approximation error processed profile and improve processing performance, due to the possibility of increasing the tool movement step.

PRECISION OF HOLE PROCESSING BY REAMER-BROACHING

"To process holes in bushings, flanges, pulleys and other similar parts, various types of metal-cutting tools are used: drills, countersinks, reamers, broaches, and others. The use of a particular tool depends on the required accuracy, roughness and type of production. Unfavorable cutting conditions cause an increase in the mechanical load on the blade section, where the chips separate from the main layer of material and its deformation, which is accompanied by significant heat release and low tool life. This article proposes the processing of high-precision holes – a reamer-broaching, the design of which is confirmed by the patents of the Republic of Kazakhstan, and structurally combines the features of a reamer and a broach. This design provides favorable cutting conditions, which contributes to high machining accuracy and low surface roughness. In cross-section, the profile of the helical teeth of the reamer-broaching can be of the following versions: standard profile of the reamer teeth, equal-wide tooth profile, like a broach with a helical equal-wide tooth, cutting-deforming. The results of production testing of samples are given, the analysis shows that the accuracy of the diametrical dimensions of the holes after processing with a reamer-broaching increased by 1.2 quality compared to a machine standard reamer; the roughness decreased by 1, 2 classes. Keywords: processing, hole, accuracy, quality, roughness, reamer, broach."

Маятниковое скрайбирование с регистрацией акустической эмиссии

Physical, mechanical and operational properties of tool materials were evaluated by various methods and techniques. However, those that allowed predicting performance of the metal-cutting tools in various operating conditions were becoming more and more in demand. The paper provides certain results of the pendulum scribing (scratching) introduction in evaluating and predicting performance of the coated tool. The parameter under study was crack resistance (resistance to formation and growth of cracks) of the tool material. The process of pendulum scribing was accompanied by registration of the acoustic emission signals. Acoustic emission was involved as a process that physically reflected alteration in the stress-strain state of the tool material.

Tribotechnical properties of high-entropic coatings for metal-cutting tools

The paper presents the results of experimental studies of tribotechnical properties of high-entropic wear-resistant coatings on cutting tools for their subsequent application in high-speed turning of heat-resistant and heat-resistant steels and alloys. High-entropic alloys and coatings represent a separate group of materials with unique properties which application under conditions of high-temperature loading and action of alternating stresses on a cutting wedge would allow significantly increasing the efficiency of blade machining by cutting. High-entropic coatings on the basis of aluminum have essentially better tribotechnical characteristics and can be used in tool production.

Основные результаты и направления дальнейших исследований по низкотемпературному плазменному формированию композитных структур на рабочих поверхностях геометрически сложных металлических изделий

The attained results and valid directions of further research on improving the efficiency of low-temperature plasma for-mation of composite structures on the functional surfaces of geometrically complicated metal products (in particular, metal-cutting tools) are conducive to improving their durability and expanding areas of application

Wear resistance of metal-cutting tools and formation of secondary contact structures during cutting

This article presents the results of research funded by the Committee of Science of the Ministry of Science and Higher Education of the Republic of Kazakhstan (grant № AP14972884 "Increasing wear resistance of metal-cutting tools by the method of lapping"). There was investigated the state of the metal-cutting tools' wear problem in the conditions of machine-building enterprises of the Republic of Kazakhstan (RK). It is revealed that metal-cutting tools do not always endure the durability period according to the standards and are exposed to premature wear of cutting edges, breakage, and chipping. The factors affecting the wear resistance of metal-cutting tools and the existing possibilities for their improvement are also studied. The article proposes the method of pretreating cutting tools in order to improve the wear resistance and durability of metal-cutting tools under the conditions of domestic machine-building industries. The formation of secondary structures on the working surfaces of the tools, which is one of the manifestations of the fundamental law - structural adaptability was studied on the basis of the results of the analysis of previously conducted works.

Investigation of wear mechanisms of multilayer nanostructured wear-resistant coatings during turning of steel. Part 2: Diffusion, oxidation processes and cracking in Ti-TiN-(Ti,Cr,Mo,Al)N coating

The paper continues the investigation focused on various factors of wear of coatings deposited on metal-cutting tools. The paper presents the results of the investigation focused on the wear process typical for tools with the Ti-TiN-(Ti,Cr,Mo,Al)N multilayer nanostructured wear-resistant coating during the turning of steel. Particular attention has been paid to the study of the diffusion of iron (Fe) from the material being machined into the coating and of coating elements into the material being machined. It has been found that the diffusion of iron into the nanolayer structure of the coating is of periodic decaying pattern. Nanolayers of the coating with the high content of Cr-Mo exhibit the best barrier functions with respect to the diffusion of iron. The investigation has revealed the active oxidation of the layer of the material being machined in contact with the coating, with the noticeable formation of individual grains of iron oxide, which can have an abrasive effect on the coating surface. The studies have detected the diffusion of iron into the coating to a depth not exceeding 300–400 nm and the diffusion of coating elements (primarily, chromium) into the material being machined to a depth not exceeding 100 nm. The process of crack formation in the coating and the role of the crystalline structure and internanolayer interfaces in the inhibition of crack propagation have been investigated.