Tool Coatings Research Articles

CONDITIONS FOR INCREASING THE EFFICIENCY OF HIGH-PERFORMANCE PROCESSING

An analytical solution is given on the conditions for reducing the technological cost of processingand the possibility of implementing high-speed cutting. It is shown that the cutting speed is limited bythe extremum (minimum) of the cost of processing. It is possible to increase the cutting speed andimplement high-speed machining conditions by increasing the tool life by using stronger and morewear-resistant tool materials and tool coatings characterized by a low coefficient of friction.

Tool Wear in Nickel-Based Superalloy Machining: An Overview

Nickel-based superalloys have been widely used in the aerospace, petrochemical, and marine fields and others because of their good oxidation resistance, corrosion resistance, stability, and reliability at various temperatures. However, as a nickel-based superalloy is a kind of processed material, in the cutting process a large amount of cutting heat is generated due to the interaction between the tool and the workpiece. At the same time, the low thermal conductivity of the workpiece causes a large amount of cutting heat to accumulate at the contact point, resulting in serious tool wear, reduced tool life, frequent tool changes, and other problems, which increase the production cost of the enterprise. This paper introduces the tool wear mechanisms (abrasive wear, adhesive wear, plastic deformation, chemical wear, etc.) in the machining process of nickel-based superalloys and summarizes the research status of failure mechanisms, tool wear optimization, etc. Based on a review of the existing research, it was found that the purpose of adding tool coatings, optimizing tool materials and cutting parameters, or improving the cutting environment is to control the heat during the processing of nickel-based superalloys to improve the tool environment and prolong the service life. The development prospects of tool wear prevention measures in the field of nickel-based alloy machining are also described.

Research on the oxidation resistance and ultra-high frequency thermal fatigue shock failure mechanisms of the bilayer and multilayer nano-coatings on cemented carbide tools

The multilayer nano-coating shows excellent thermal stability and oxidation resistance which could be attributed to the multielement composition and multilayer structure. It is widely used in the machining of hard-to-cut materials, such as titanium alloy. The formation of serrated chip during cutting process of Ti-6Al-4V would result in the ultra-high frequency thermal fatigue shock on the coating surface, and this could induce the thermal fatigue failure of coating. In this study, the ultra-high frequency (20 kHz) thermal fatigue shock testing was developed to investigate the thermal fatigue failure mechanisms of the bilayer TiSiN/TiAlN coating and multilayer TiSiN/TiAlN nano-coating. It was achieved by using the pulsed laser system to irradiate the coating surface under different shock cycles, which could produce alternating thermal stress on coating surface. This creates a close simulation of the actual working conditions in high-speed machining of Ti-6Al-4V with serrated chip produced. Moreover, the high temperature oxidation experiments were performed to study the oxidation resistance of coating. The failure mechanisms of coating/substrate system under the constant thermal loads and dynamic thermal loads were compared and analyzed. The cutting performance of related coated tools was evaluated after turning Ti-6Al-4V. The correlation between the thermal fatigue shock resistance of coatings at ultra-high frequency and the wear behavior of coated tools was built. It can be concluded that the multilayer TiSiN/TiAlN nano-coating showed better properties of the resistance to thermal fatigue shock in machining Ti-6Al-4V.

Design Optimization for the Coating of Machine Tools Based on Eye-Tracking Experiments and Virtual Reality Technology

The coating design of machine tools refers to the exterior appearance of a machine tool and is an important method for improving the user experience and brand image. In this study, we studied and optimized the coating design of serial CNC cylindrical grinder machines of the Shanghai Machinery Factory in China using eye-tracking experiments and virtual reality technology. Firstly, based on eye-tracking technology, experiments were carried out on various elements of the coating design of the machine tools. Secondly, the experimental data were analyzed to extract design criteria that fit the user’s visual habits and to determine the details of the coating design optimization. Thirdly, the design scheme was verified using virtual reality technology and a user questionnaire survey. The results show that it provides support for the optimization of the design and working efficiency of machine tool coatings in enterprises. Future work should investigate optimization design tools that include ergonomics based on vision experiments and virtual reality.

Effect of Tool Coatings on Machining Properties of Compacted Graphite Iron.

Compacted graphite iron (CGI) has become the most ideal material for automotive engine manufacturing owing to its excellent mechanical properties. However, tools are severely worn during processing, considerably shortening their lifespan. In this study, we prepared a series of cemented carbide-coated tools and evaluated their coating properties in cutting tests. Among all tested coatings, PVD coating made of AlCrN (AC) presented with the best surface integrity and mechanical properties, achieving the best comprehensive performance in the coating test. The AC-coated tool also exhibited the best cutting performance at a low speed of 120 m/min, corresponding to a 60% longer cutting life and the lowest workpiece surface roughness relative to other coated tools. In the cutting test at a high speed of 350 m/min, the CVD double-layer coated tool (MT) with a TiCN inner layer of and an Al2O3 outer layer had a 70% longer cutting life and the lowest workpiece surface roughness relative to other coated tools.

Comparing the performance of several tool coatings in turning of commercially pure titanium grade 4

The increasing use of titanium and its alloys in the manufacture of implants results from the simultaneous presence of excellent biocompatibility, relatively low density, high mechanical properties, and corrosion resistance. Unlike the excellent application characteristics, titanium is classified as a difficult-to-machine material. Therefore, one constant challenge for implant manufacturers is to correctly choose turning tools for each application. This work aims to compare the useful life of the uncoated insert with other three types of coatings on carbide tools, titanium aluminum nitride (TiAlN), aluminum chromium nitride (AlCrN), and titanium nitride/titanium carbonitride multilayer coating (TiN + TiCN). Turning experiments were performed using grade 4 commercially pure titanium (typically used in dental implants), testing two cutting speeds for each tool used. The tests were carried out in a CNC rotary head lathe, using cutting fluid in abundance. The results showed that the uncoated insert achieved the shortest life due to its worst properties (lower surface hardness, higher friction coefficient, and lower maximum working temperature), even with its supposedly higher chemical stability with titanium. On the other hand, the tool with the TiN + TiCN multilayer coating obtained the longest tool life among the four tested inserts. The main novelty of this work is that the tool that showed the longest life (TiN + TiCN coating) did not have the best properties among the tested coatings. In fact, it had both the lowest hardness and working temperature. However, this tool has a low coefficient of friction and a multilayer structure coating, which increases its resistance against the wear mechanism that occurred predominantly in this application, which was attrition. Even with the increased cutting speed, this coating also achieved the best result. Therefore, during the machining of titanium, the most important characteristics of the tool are low coefficient of friction and resistance against the pull out of particles.

Tool and formability multi-response optimization for ultimate strength and ductility of AA8011 during axial compression

Friction stir incremental forming is a dieless forming process achieved through the severe plastic deformation of sheet metals by localized heat through tool friction with sheet metal. Tool rotation contributes significantly to determining the local heat generation and deformation of the sheets. In this study, a novel attempt was made to improve the desired surface quality with minimum tool wear using three different tool coatings. To identify the optimal parameters, process factors such as spindle speed, step size, and table feed were considered with two response parameters forming force and surface roughness. A total of 27 experiments based on a full factorial design were performed. During this optimization using TOPSIS, parameters are selected based on which FSIF parts should attain the minimum forming force and surface roughness. Based on the results obtained, the titanium nitride coating in the tool enhanced the surface roughness and increased the maximum formability. This study provides an optimal parameter setting for AA8011 and an understanding of the friction stir effect during the incremental forming process.

Temperature-dependent tribological behavior of CrAlN/TiSiN tool coating sliding against 7A09 Al alloy and GCr15 bearing steel

Tool coatings exhibit different tribological behavior when cutting dissimilar materials, and understanding the differences is crucial for their service life. In this study, CrAlN/TiSiN multilayer coating was deposited by the arc ion plating technique, and its microstructure, load-bearing capacity, and toughness were investigated as well as the tribological behavior of the coating sliding against 7A09 Al alloy and GCr15 bearing steel at different temperatures. The results indicated a high fluctuation in the friction coefficient between the coating and 7A09 Al alloy above 150 °C, and the coating exhibited a negative wear rate. The friction coefficient between the coating and GCr15 bearing steel shows a decreasing trend above 150 °C, and the wear surface of the coating showed a smooth morphology.

Self-lubricating CrAlMoN high performance tool coatings for machining of TiAl6V4

TiAl6V4 allows significant performance improvements in industrial applications. However, the machining is a considerable challenge due to low thermal conductivity, Young’s modulus and strong adhesion tendency. This leads to high thermal and mechanical loads on the cutting edge resulting in early tool failure. Today, uncoated cemented carbide tools are commonly used. However, temperature active physical vapor deposition (PVD) coatings like CrAlVN and CrAlMoN provide a promising approach to increase tool life. For this, the coating’s ability to form lubricating oxide phases is vital. In the present study, CrAlVN and CrAlMoN coatings were investigated to determine the more suitable version for increasing the economic efficiency of machining TiAl6V4. The coatings were deposited by hybrid direct current magnetron sputtering/high power pulsed magnetron sputtering (dcMS/HPPMS) processes. Morphology, thickness, chemical composition, indentation hardness, indentation modulus and oxide phase composition were analyzed. Moreover, friction and wear behavior of the coated tools were determined using a pin on disc (PoD) tribometer at various temperatures. Additionally, tool life and deformation behavior were analyzed after turning TiAl6V4. The CrAlVN and CrAlMoN coatings show a dense morphology and a smooth surface topography. Both variants have a good adhesion to the cemented carbide tools. For increased temperatures, the tribological analyses showed a reduction in the coefficient of friction. In case of CrAlMoN coated samples, a friction reduction compared to CrAlVN was observed at lower temperatures. Due to this, an increased tool life was achieved for CrAlMoN coated cutting inserts during turning of TiAl6V4.

Oral health and the presence of infectious microorganisms in hospitalized patients: a preliminary observational study

Objective Characterise oral health, and the presence in the oral cavity of pathogenic non-oral microorganisms potentially associated with nosocomial infections and antimicrobial resistance in non-intubated patients admitted to a Brazilian university hospital. Materials and methods An intraoral examination and oral swab were performed on hospitalized individuals at three different times, T1 (within 48 h of hospitalization), T2 (48 h after T1) and T3 (7 days after hospitalization). The oral health status was defined by the Oral Health Assessment Tool (OHAT) and Tongue Coating Status (TCS). The swabs were processed and microorganisms potentially related to nosocomial infections were phenotypically identified through colony morphology, staining and microscopy. Results The most prevalent microorganisms were Escherichia coli, Enterococcus spp., Enterobacter spp., Pseudomonas spp., Candida albicans and Staphylococcus aureus. The oral health status was considered median, and the tongue coating index was considered high throughout the study period. The prevalence of potentially pathogenic non-oral microorganisms was high and constant from the first 48 h to the seventh day of hospitalization. Conclusions The results point out that the mouth can act as a reservoir of epidemiologically important pathogens within hospital settings, even in patients without mechanical ventilation, thus increasing the risk of nosocomial infections in susceptible individuals. KEY MESSAGES The present study investigated the oral health status and the presence of pathogenic non-oral microorganisms in the oral cavity of patients hospitalized in the ward, non-intubated and mostly independent of self-care. The presence in the mouth of microorganisms related to the epidemiology of nosocomial infections and resistance to antimicrobials was high and constant from the first 48 h to the 7th day of hospitalization. The results of this study point out that the mouth can act as a reservoir of epidemiologically important pathogens within hospital settings even in patients without mechanical ventilation, increasing the risk of nosocomial infections in susceptible individuals.

Characterization and Evaluation of Engineered Coating Techniques for Different Cutting Tools-Review.

Coatings are now frequently used on cutting tool inserts in the metal production sector due to their better wear resistance and heat barrier effect. Protective hard coatings with a thickness of a few micrometers are created on cutting tools using physical or chemical vapor deposition (PVD, CVD) to increase their application performance. Different coating materials are utilized for a wide range of cutting applications, generally in bi-or multilayer stacks, and typically belong to the material classes of nitrides, carbides, carbonitrides, borides, boronitrides, or oxides. The current study examines typical hard coatings deposited by PVD and CVD in the corresponding material classes. The present state of research is reviewed, and pioneering work on this subject as well as recent results leading to the construction of complete “synthesis–structure–property–application performance” correlations of the different coatings are examined. When compared to uncoated tools, tool coatings prevent direct contact between the workpiece and the tool substrate, altering cutting temperature and machining performance. The purpose of this paper is to examine the effect of cutting-zone temperatures on multilayer coating characteristics during the metal-cutting process. Simplified summary and comparisons of various coating types on cutting tools based on distinct deposition procedures. Furthermore, existing and prospective issues for the hard coating community are discussed.

Influence of crystallographic texture on friction in α-Al2O3/Ti(C,N) ceramic tool coatings

This work explores the influence of the crystallographic texture on the resulting frictional response in two ceramic coatings systems containing top α-Al2O3 layer with no and fiber texture. The microstructure was analyzed by electron backscatter diffraction, the surface roughness was characterized by white light interferometry, and the micro hardness was measured by standard Vickers testing. The coefficient of friction (COF) was measured using ball-on-disk tribometry under linear reciprocating sliding motion. Our results verified a strong correlation between the crystallographic texture of the top α-Al2O3 layer and the resulting COF. This effect can be mainly attributed to the lowest critical shear stress within the basal dislocation slip {0001} <11-20>, which facilitates the generation of plastic deformation at the top surface layer. This work highlights the understanding of the complex correlations between microstructure and tribological performance of ceramic coatings.

State of the art review on the sustainable dry machining of advanced materials for multifaceted engineering applications: progressive advancements and directions for future prospects

In this article, the comprehensive review on the application, and indeed, a comparative analysis on dry machining of different types of materials (Inconel, steel, aluminum, cast iron, magnesium and advanced materials) used in machining (turning, drilling and milling operations) were carried out in the light of utmost works published in the literature. The work describes the scientific findings of the past twenty years, including sustainable methods (surface texture, solid lubricants, vibration-assisted machining, laser-assisted machining), tool coatings, and geometry of tools. Vibration-assisted machining is another direction that researchers have investigated without the use of cutting coolants, where the complete disposal of coolants is not possible. Various researchers have carried out rigorous experimental work on milling, drilling, and turning operations under dry conditions to machine numerous materials. A significant proportion of experimental data about tool wear, tool wear machining, surface quality, surface integrity, etc, has been analyzed under dry conditions. However, the critical analysis of dry machining for different conventional machining operations for a variety of industrial materials is still lacking for establishing dry machining as a sustainable process for industrial applications. Thus, the critical analysis of various machining parameters and their consequences on tool wear and the surface quality of machined work was carried out in this work. Finally, scientific recommendations based on critical findings were proposed for industrial implementation of dry machining.

Effect of volcano-like textured coated tools on machining of Ti6Al4V: an experimental and simulative investigation

The present study was to reduce the adhesion and wear that happened on the rake face during machining of Ti6Al4V alloys by employing volcano-like textured coated tools. A combination of experimental and simulative investigation was adopted. DEFORM-3D software with updated Lagrangian formulation was used for numerical simulation, and the thermo-mechanical analysis was performed using Johnson–Cook material model to predict the cutting forces, cutting temperature, chip morphology, and tool wear. In cutting experiments, volcano-like textures with different area densities (10%, 20%, 30%) were fabricated by fiber laser on the rake face of cemented carbide tools close to the main cutting edge. Then, these textured tools were deposited with CrAlN coating through cathodic vacuum arc ion plating technique. Experiments in cutting Ti6Al4V alloys were carried out with the textured coated tools and non-textured coated tool under dry and wet cutting conditions. Then, cutting forces, chip morphology, and tool wear were investigated. The results showed that textured coated tools were superior to the conventional tool. Especially in wet cutting, the main cutting force and radial force of the coated tool with texture area density of 20% (VCT2) were reduced by 11.6% and 21.25%, respectively. Surface morphology of VCT2 tool had lower workpiece adhesion on the rake face. Therefore, VCT2 tool showed a better cutting performance. Finally, the mechanisms of textured coated tools under wet cutting conditions were proposed.

Advances in binary nitride coatings for cemented carbides

Abstract With the development of science and technology, cemented carbide tool coatings for machining are updating constantly. Different chemical elements in tool coatings have different performance. This paper introduces the current status of the use of various chemical elements in carbide tool coatings, common chemical elements include metallic elements (transition metal elements, rare-earth elements and aluminium elements) and non-metallic elements (silicon and boron). In addition, this paper presents the current status of research on related basic coatings which includes CrN, TiN, TiCN and CrCN coating, and it looks ahead the develop of tool coating prospect as well.

Influence of the Tool Wear on the Quality and Service Life of Gears for the Geared Turbofan Technology Machined by Five-Axis Milling

Abstract The geared turbofan technology is one essential way to reduce the fuel consumption, the environmental footprint, and the noise pollution of civil aircrafts. An added gearbox between the fan and the low-pressure compressor that reduces the fan speed, which allows higher bypass ratios, achieves the mentioned benefits of geared turbofans. To withstand the high mechanical loads, large double helical gears are used. Gear hobbing and gear grinding require large tool maneuvering spaces. This leads to a larger required space between the single gears of the double helical gear. As a result, the gears are larger and heavier, which lead to a reduced economy of the aircraft. The tool maneuvering space of five-axis milling with solid carbide end mills is much smaller. This enables the design of smaller, lighter, and more efficient aircraft engines. However, manufacturing these gears in tolerances better than IT5 is very challenging on five-axis milling machine tools. This paper presents investigations about finish machining of hardened gears on five-axis machine tools. In the investigations performed, varying tool substrates and tool coatings have been investigated together with tool travel paths in order to reduce the tool wear, which is key to achieve the demanded tolerances. Finally, the five-axis milled gears were compared to conventionally manufactured gears on test benches to enable statements regarding the expectable service lives of the manufactured gears.

Effects of tool coating materials and coating thickness on cutting temperature distribution with coated tools

AbstractCoated tools are currently widely used tool technology in machining. The influence of tool coating on heat transfer has become an active field of research enjoying constantly increasing attention in the field of machining. This paper is devoted to the cutting temperature in machining H13 hardened steel with monolayer coated tools (TiN, TiAlN, and Al2O3) and multilayer coated tools (TiN/TiC/TiN and TiAlN/TiN). Equivalent composite thermal conductivity and thermal diffusivity of multilayer coated tools were calculated using the equivalent approach. The established heat transfer analytical models estimated coating temperature in turning. The effect of tool coating in steady and transient heat transfer was studied, as well as the cutting temperature distribution. It reveals that the tool coating material and coating thickness can influence the cutting temperature distribution of coated tool. Thermal conductivity of coating material affects the steady cutting temperature distribution, and thermal diffusivity of coating material affects the transient cutting temperature distribution of coating tools.

ТВЁРДОСПЛАВНЫЕ ПЛАСТИНЫ И ПОКРЫТИЯ К НИМ ДЛЯ ТОЧЕНИЯ ТРУДНООБРАБАТЫВЕМЫХ НЕРЖАВЕЮЩИХ СТАЛЕЙ

The work objective. To increase by 2-3 times the life of replaceable carbide inserts when turning specialized hard-to-machine stainless steels, The problem to which the paper is devoted. To identify some of the most rational new coatings for carbide tools designed for turning specialized stainless steels.&#x0D; Research methods. The method of simulation modelling is applied for predictive design of a carbide tool with coatings.&#x0D; The novelty of the work. The scientific novelty of the research consists in the development of scientific principles and innovative technologies based on plasma coating processes by condensation with ion bombardment (CIB) with the prediction of adaptive response to external influences for the purpose of application in treatment of hard-to-machine stainless steels. The results of the study. A sequence of actions (methodology) is developed to design coatings for turning tools under the specified conditions of their operation. A number of coatings are proposed that provide an increase in the tool life by two times or more to wear 0.5 mm on the back surface of the tool. Regression (polynomial) equations are developed that characterize the dependence of the wear value of the tool on the time of its operation when turning these stainless steels.&#x0D; Conclusion. Scientific principles and innovative technologies are developed based on plasma coating processes by condensation with ion bombardment (CIB) with prediction of adaptive response to external influences for the purpose of application in treatment of hard-to-machine stainless steels. This made it possible to develop recommendations that ensure an increase in the performance of domestic standard carbide tools by 2-4 times over the period of operation up to 0.5 mm wear, the possibility of choosing the most rational tool materials for the specified or expected conditions of their operation, optimizing the parameters of the cutting mode, increasing treatment productivity without reducing the quality of the treated surface, the possibility to order the necessary cutting tool reasonably. Methods for designing new tools for the specified or desired conditions of their operation are developed. They provide to control the tool operability to ensure its necessary level, desired quality of the treated surface and the necessary treatment performance.

High-temperature tribological behavior of Ti containing diamond-like carbon coatings with emphasis on running-in coefficient of friction

Diamond-like carbon (DLC) coatings show a low coefficient of friction (COF) and high wear resistance against aluminum at elevated temperatures, yet they exhibit a high running-in COF (μ R ) prior to reaching a low and stable steady-state COF (μ s ). This study shows that incorporating titanium (Ti) atoms into the DLC structure would reduce the μ R . During pin-on-disk tests conducted on Ti incorporating hydrogenated-DLC (Ti-H-DLC) with 6.2 at.% Ti subjected to dry sliding against 319 Al (Al-6.5% Si), μ s values decreased from 0.27 at 25 °C to 0.11 at 200 °C. The specific wear rate of Ti-H-DLC decreased from 2.44 × 10 −5 mm 3 /Nm at 25 °C to 0.71 × 10 −5 m 3 /Nm at 200 °C. A typical DLC with 40 at.% H (H-DLC) tested at 200 °C showed a low μ s of 0.08 and a wear rate of 1.11 × 10 −5 mm 3 /Nm. However, at 200 °C, Ti-H-DLC showed a lower μ R of 0.16 compared to μ R = 0.78 of H-DLC, and the duration of the running-in period for Ti-H-DLC, t R = 3 revolutions, was shorter than H-DLC with t R of 200 revolutions. Comparisons made with other DLCs, including, NH-DLC, W-DLC, ta-C, and Si-O-H-DLC, in addition to H-DLC, all tested using the same method, revealed that, in the temperature range of 100–250 °C, Ti-H-DLC showed a better running-in behavior making Ti-H-DLC a suitable tool coating for manufacturing processes where high-temperature running-in sliding friction is important, including warm forming and (single-point) turning of aluminum alloys . • High-temperature tribological behavior of Ti-H-DLC against 319 Al was studied. • Low running-in COF and short running-in duration were recorded at 100 and 200 °C. • Compared to other DLC coatings, the lowest μ R and t R were obtained using Ti-H-DLC. • Ti-H-DLC tool coatings are useful for Al warm forming, machining operations ~200 °C.

Machining parameter comparison on HSS cutting tool coated with multi-walled carbon nano tube using green coating technique

The current study focuses on nanocoating and its examination on HSS (tool bit) using the Physical Vapor Deposition technique. Multiwall Carbon nanotube (MWCNT) nanoparticles are deposited on an HSS Steel tool bit in this process to determine the enhancement and efficiency of the coatings. Various machining variables are used to compare uncoated and coated tool bits. During the procedure, many other process parameters such as surface roughness and tool wear were also studied out. The results show that after coating with Multiwall Carbon nanotube (MWCNT) the properties get improved and, it has been determined that the coated Multiwall Carbon nanotube (MWCNT) tool has a greater lifetime, wear resistance, hardness, and surface quality than the coated tool.