Research on Coated Tool Life and Wear in Ta-2.5W Alloy Turning

Due to its inherent high hardness, strength, and plasticity, tantalum-tungsten (Ta-W) alloy poses a considerable challenge in machining, resulting in pronounced tool wear, diminished tool lifespan, and suboptimal surface quality. This study undertook experiments utilizing uncoated carbide tools, TiAlN-coated carbide tools, and AlTiN-coated carbide tools for machining Ta-2.5W alloy. The investigation delved into the intricacies of surface temperature, tool longevity, and the distinctive wear characteristics under varying coating materials and cutting parameters. Concurrently, a comprehensive exploration of the wear mechanisms affecting the tools was conducted. Among the observed wear modes, flank wear emerged as the predominant issue for turning tools. Across all three tool types, adhesive wear and diffusion wear were identified as the principal wear mechanisms, with the TiAlN-coated tools displaying a reduced level of wear compared to their AlTiN-coated counterparts. The experimental findings conclusively revealed that TiAlN-coated carbide tools exhibited an extended tool lifespan in comparison to uncoated carbide tools and AlTiN-coated carbide tools, signifying superior cutting performance.

Measurement of Cutting Temperature in Interrupted Machining Using Optical Spectrometry

This research presents an experimental study focused on measuring temperature at the tool flank during the up-milling process at high cutting speed. The proposed system deals with emissivity compensation through a two-photodetector system and during calibration. A ratio pyrometer composed of two photodetectors and a multimode fiber-optic coupler is employed to capture the radiation emitted by the cutting insert. The pyrometer is calibrated using an innovative calibration system that addresses theoretical discrepancies arising from various factors affecting the measurement of cutting temperature. This calibration system replicates the milling process to generate a calibration curve. Experimentally, AISI 4140 steel is machined with coated tungsten carbide inserts, using cutting speeds of 300 and 400 m/min, and feed rates of 0.08 and 0.16 mm/tooth. The results reveal a maximum recorded cutting temperature of 518 °C and a minimum of 304 °C. The cutting temperature tends to increase with higher cutting speeds and feed rates, with cutting speed being the more influential factor in this increase. Both the pyrometer calibration and experimental outcomes yield satisfactory results. Finally, the results showed that the process and the device prove to be a convenient, effective, and precise method of measuring cutting temperature in machine processes.

Review of Cutting Temperature Measurement Methods

During the cutting process, large quantities of emitted heat are concentrated on a small surface area of the interface between the workpiece and the cutting edge. The resultant very high temperature significantly affects the tool life. Knowledge of maximum temperatures to be expected on the cutting edges is important, as it allows the cutting conditions to be adjusted in such a manner that the critical value of thermal resistance is not exceeded for the cutting material. In effect, the maximum effectiveness of the working process is maintained. This article offers a systematic presentation of methods used in cutting temperature measurements. It discusses their advantages and disadvantages, as well as the usefulness of the individual methods in different types of machining processes. It also points to the possibility of methodological errors which significantly reduce measurement accuracy. The above issues are believed to justify a discussion of different cutting temperature measurement methods. The conclusions here presented may be of particular importance to researchers interested in the field, especially in high-efficiency machining, new cutting materials and cutting-edge protective coatings, as well as various methods for cutting fluid applications. They may allow a more informed selection of measurement methods most suitable for particular situations.

Application of Nanofluids for Machining Processes: A Comprehensive Review

According to the demand of the present world, as everything needs to be economically viable and environment-friendly, the same concept applies to machining operations such as drilling, milling, turning, and grinding. As these machining operations require different lubricants, nanofluids are used as lubricants according to the latest technology. This paper compares different nanofluids used in the same machining operations and studies their effects. The variation in the nanofluid is based on the type of the nanoparticle and base fluid used. These nanofluids improve the lubrication and cooling in the machining operations. They also aid in the improvement in the surface roughness, cutting forces, cutting temperature of the workpiece, and tool life in the overall process taking place. It is worth noting that nanofluids are more effective than simple lubricating agents. Even within the nanofluid, the hybrid type is the most dominating, and helps to obtain a maximum efficiency through certain machining processes.

Temperature Measurement during Abrasive Water Jet Machining (AWJM)

This study was undertaken to look for confirmation that heat transfer induced by abrasive water jet machining (AWJM) affects the microstructure of the material cut. The structure of S235JR carbon steel used in the experiments was reported to change locally in the jet impact zone due to the high concentration of energy generated during cutting with the abrasive water jet. It is assumed that some of the energy is transferred into the material in the form of heat. This is particularly true for materials of considerable thickness with a high thermal conductivity coefficient when cutting is performed at low speeds or with high abrasive consumption. The literature on the subject suggests that in AWJM there is little or no thermal energy effect on the microstructure of the material cut. The research described here involved the measurement of the cutting temperature with thermocouples placed at four different distances from the edge. The distances were measured using computed tomography inspection. The thermocouples used in the tests were capable of detecting temperatures of up to 100 °C. Locally, temperatures at the edge may reach much higher values. The results of the X-ray diffraction qualitative phase analysis reveal that locally the temperatures may be much higher than the eutectoid temperature. Phase changes occurred along the edge since austenite was observed. This suggests that the temperature in the jet impact zone was much higher than the eutectoid temperature. Optical microscopy was also employed to study the material microstructure. Finally, the material nanohardness was determined.

Computational Fluid Dynamics Simulation on Thermal Performance of Al/Al2O3/SWCNT Nanocoolants for Turning Operations

The objective of this study is to numerically investigate the thermal performance of cutting fluids dispersed with nanoparticles for effective heat removal during turning operations. The simulations are performed using Ansys Fluent software, and the problem is modelled as a three-dimensional turbulent incompressible single-phase flow. The computational domain consists of a heated cutting tool and work piece, and nanocoolants are sprayed from a nozzle located above the machining zone. The nanocoolants are prepared by mixing mineral oil with nanoparticles of Al₂O₃ (Aluminium Oxide), Al (Aluminium) and SWCNT (Single Walled Carbon Nanotube). The heat transfer performances of different nanocoolants are compared by varying the nanoparticle volume fraction (φ) and coolant velocity (U_c) in the range of 2% ≤ φ ≤ 8% and 1 m/s ≤ U_c ≤ 15 m/s, respectively. The results indicated a drastic drop in the cutting tool temperature with an increase in the volume fraction of dispersed nanoparticles and coolant velocity. The increase in volume fraction decreases the average cutting tool temperature by 25.65% and also enhances the average heat transfer rate by 25.43%. It is additionally observed that SWCNT nanocoolants exhibited a superior thermal performance and heat removal rate compared with Al and Al₂O₃ nanocoolants. The analysed numerical results are validated and are in good accordance with the benchmark results validated from literature.

Predictive Analytical Modeling of Thermo-Mechanical Effects in Orthogonal Machining

Factor relationships in a machining system do not work in pairs. Varying the cutting parameters, materials machined, or volumes produced will influence many machining characteristics. For this reason, we are attempting to better understand the effect of the Johnson-Cook (J-C) law of behavior on cutting temperature prediction. Thus, the objective of the present study is to investigate, experimentally and theoretically, the tool/material interactions and their effects on dust emission during orthogonal cutting. The proposed approach is built on three steps. First, we established an experimental design to analyze, experimentally, the cutting conditions effects on the cutting temperature under dry condition. The empirical model which is based on the response surface methodology was used to generate a large amount of data depending on the machining conditions. Through this step, we were able to analyze the sensitivity of the cutting temperature to different cutting parameters. It was found that cutting speed, tool tip radius, rake angle, and the interaction between the cutting speed and the rake angle explain more than 84.66% of the cutting temperature variation. The cutting temperature will be considered as a reference to validate the analytical model. Hence, a temperature prediction model is important as a second step. The modeling of orthogonal machining using the J-C plasticity model showed a good correlation between the predicted cutting temperature and that obtained by the proposed empirical model. The calculated deviations for the different cutting conditions tested are relatively acceptable (with a less than 10% error). Finally, the established analytical model was then applied to the machining processes in order to optimize the cutting parameters and, at the same time, minimize the generated dust. The evaluation of the dust generation revealed that the dust emission is closely related to the variation of the cutting temperature. We also noticed that the dust generation can indicate different phenomena of fine and ultrafine particles generation during the cutting process, related to the heat source or temperature during orthogonal machining. Finally, the effective strategy to limit dust emissions at the source is to avoid the critical temperature zone. For this purpose, the two-sided values can be seen as combinations to limit dust emissions at the source.

Temperature Distribution Simulation, Prediction and Sensitivity Analysis of Orthogonal Cutting of Cortical Bone

Bone cutting plays an important role in spine surgical operations. The power devices with high speed employing in bone cutting usually leads to high cutting temperature of the bone tissue. This high temperature control is important in improving cutting surface quality and optimizing the cutting parameters. In this paper, the bone-cutting model was appropriately simplified for finite element (FE) based modeling of 2D orthogonal cutting to discuss the change law of cutting temperature of cortical bones for cervical vertebra, and to study the orthogonal cutting mechanism of the anisotropic cortical bone, a 3D FE simulation model had been also established in which longitudinal, vertical, and transversal cutting types were accomplished to investigate the effect of osteons orientation. Secondly, this response surface method was used to regress the simulation results, and establishes the prediction model of maximum temperature on cutting depth, cutting speed, and feed speed. Then, the Sobol method was used to analyze the sensitivity of the milling temperature prediction mathematical model parameters, in order to clarify and quantitatively analyze the influence of input milling parameters on the output milling temperature. Finally, the cutting temperatures obtained with the simulations were compared with the corresponding experimental results obtained from the bone milling tests. This study verifies the influence of key variables and the cutting parameters on thermo mechanical behavior of the bone cutting. The obtained cutting temperature distribution for the bone surfaces could be employed to establish a theoretical foundation for research on thermal damage control of bone tissues.

Influence of Microgroove Structure on Cutting Performance and Chip Morphology during the Turning of Superalloy Inconel 718

This study designed a new microgroove cutting tool to machine Inconel 718 and focused on the effect of microgroove structure on the cutting performance and chip morphology during the turning. A comparative analysis of the cutting force, cutting temperature, tool life, tool wear, and chip morphology of the microgroove cutting tool and the original cutting tool was conducted. The main cutting force and temperature of the microgroove cutting tool were reduced by 12% and 12.17%, respectively, compared with the original cutting tool. The microgroove cutting tool exhibited a significant improvement compared with the original cutting tool, which extended the tool life by up to 23.08%. Further, the microgroove cutting tool distorted the curl radius of the chips extensively. The experimental results showed that the microgroove structure can not only improve the tool life, but also improve the chip breaking effect.

Modelling and Prediction of Cutting Temperature in the Machining of H13 Hard Steel of Transient Heat Conduction

Cutting heat conduction undergoes three stages that include intensity transient-state, transient-state, and steady-states. Especially during machining with coated cutting tools, in the conduction process, cutting heat needs to pass through a few micron thick coatings and then flow into the tool body. This heat conduction presents typical non-Fourier heat conduction characteristics. This paper focuses on the cutting temperature in transient heat conduction with a coated tool. A new analytical model to characterize the thermal shock based on the non-Fourier heat conduction was proposed. The distribution of cutting temperature in mono-layer coated tools during the machining was then illustrated. The cutting temperature distribution predicted by the Fourier heat conduction model was employed to compare with that by non-Fourier heat conduction in order to reveal the non-Fourier heat conduction effect in transient heat conduction. The results show that the transient heat conduction analytical model is more suitable for the intensity transient-state and transient-state in the process of cutting heat conduction.

Approximately Model of the Maximum Temperature on the Chip Surface

This article presents an approximately model that allows for the determination of the maximum temperature of the chip surface in dry orthogonal turning. The mathematical formula describing the maximum temperature of the chip surface was formulated based on experimental data. The experiments were carried out for orthogonal cutting of austenitic steel AISI 321 with flat rake face carbide inserts that were made of tungsten carbide H10F, both uncoated and coated, with coatings of varied arrangement. Thermographic images of the cutting zone were used to verify the correctness of the approximately model. The obtained results show good agreement between the modelling results and experimental studies. The discrepancy of the maximum temperature values of the top surface of the chip does not exceed 6.4%.

Precision Hard Turning of Ti6Al4V Using Polycrystalline Diamond Inserts: Surface Quality, Cutting Temperature and Productivity in Conventional and High-Speed Machining

This article presents the results of an experimental investigation into the machinability of Ti6Al4V alloy during hard turning, including both conventional and high-speed machining, using polycrystalline diamond (PCD) inserts. A central composite design of experiment procedure was followed to examine the effects of variable process parameters; feed rate, cutting speed and depth of cut (each at five levels) and their interaction effects on surface roughness and cutting temperature as process responses. The results revealed that cutting temperature increased with increasing cutting speed and decreasing feed rate in both conventional and high-speed machining. It was found that high-speed machining showed an average increase in cutting temperature of 65% compared with conventional machining. Nevertheless, high-speed machining showed better performance in terms of lower surface roughness despite using higher feed rates compared to conventional machining. High-speed machining of Ti6Al4V showed an improvement in surface roughness of 11% compared with conventional machining, with a 207% increase in metal removal rate (MRR) which offered the opportunity to increase productivity. Finally, an inverse relationship was verified between generated cutting temperature and surface roughness. This was attributed mainly to the high cutting temperature generated, softening, and decreasing strength of the material in the vicinity of the cutting zone which in turn enabled smoother machining and reduced surface roughness.

Intelligent Optimization of Hard-Turning Parameters Using Evolutionary Algorithms for Smart Manufacturing

Recently, the concept of smart manufacturing systems urges for intelligent optimization of process parameters to eliminate wastage of resources, especially materials and energy. In this context, the current study deals with optimization of hard-turning parameters using evolutionary algorithms. Though the complex programming, parameters selection, and ability to obtain the global optimal solution are major concerns of evolutionary based algorithms, in the present paper, the optimization was performed by using efficient algorithms i.e., teaching⁻learning-based optimization and bacterial foraging optimization. Furthermore, the weighted sum method was used to transform the diverse responses into a single response, and then multi-objective optimization was performed using the teaching⁻learning-based optimization method and the standard bacterial foraging optimization method. Finally, the optimum results reported by these methods are compared to choose the best method. In fact, owing to better convergence within shortest time, the teaching⁻learning-based optimization approach is recommended. It is expected that the outcome of this research would help to efficiently and intelligently perform the hard-turning process under automatic and optimized environment.

Experimental Study on Drilling MDF with Tools Coated with TiAlN and ZrN

There is increasing use of wood-based composites in industry not only because of the shortage of solid wood, but above all for their better properties such as: strength, aesthetic appearance, etc., compared to wood. Medium density fiberboard (MDF) is a wood-based composite that is widely used in the furniture industry. The goal of the research conducted was to determine the effect of the type of coating on the drill cutting blades on the value of thrust force (F_t), cutting torque (M_c), cutting tool temperature (T) and surface roughness of the hole in drilling MDF panels. In the tests, three types of carbide drills (HW) were used: not coated, TiAlN coated and ZrN coated. The measurement of both the thrust force and the cutting torque was carried out using an industrial piezoelectric sensor. The temperature of the cutting tool in the drilling process was measured using an industrial temperature measurement system using a K-type thermocouple. It was found that the value of the maximum temperature of the tool in the drilling process depends not only on the cutting speed and feed rate, but also on the type of coating of the cutting tool. The value of both the cutting torque and the thrust force is significantly influenced by the value of the feed rate and the type of drill coating. The effect of varying plate density on the surface roughness of the hole and the variation of the value of the thrust force is also discussed. The results of the investigations were statistically analyzed using a multi-factorial analysis of variance (ANOVA).

A Study on Drilling High-Strength CFRP Laminates: Frictional Heat and Cutting Temperature

High-strength carbon fiber reinforced polymer (CFRP) composites have become popular materials to be utilized in the aerospace and automotive industries, due to their unique and superior mechanical properties. An understanding of cutting temperatures is rather important when dealing with high-strength CFRPs, since machining defects are likely to occur because of high temperatures (especially in the semi-closed drilling process). The friction behavior at the flank tool-workpiece interface when drilling CFRPs plays a vital role in the heat generation, which still remains poorly understood. The aim of this paper is to address the friction-induced heat based on two specially-designed tribometers to simulate different sliding velocities, similar to those occurring along the flank tool-work interface in drilling. The elastic recovery effect during the drilling process was considered during the tribo-drilling experiments. The drilling temperatures were calculated by the analytical model and verified by the in-situ experimental results gained using the embedded thermocouples into the drills. The results indicate that the magnitudes of the interfacial friction coefficients between the cemented carbide tool and the CFRP specimen are within the range between 0.135–0.168 under the examined conditions. Additionally, the friction caused by the plastic deformation and elastic recovery effects plays a dominant role when the sliding velocity increases. The findings in this paper point out the impact of the friction-induced heat and cutting parameters on the overall drilling temperature.

Investigation of Cutting Temperature during Turning Inconel 718 with (Ti,Al)N PVD Coated Cemented Carbide Tools

Physical Vapor Deposition (PVD) Ti_1−xAl_xN coated cemented carbide tools are commonly used to cut difficult-to-machine super alloy of Inconel 718. The Al concentration x of Ti_1−xAl_xN coating can affect the coating microstructure, mechanical and thermo-physical properties of Ti_1−xAl_xN coating, which affects the cutting temperature in the machining process. Cutting temperature has great influence on the tool life and the machined surface quality. In this study, the influences of PVD (Ti,Al)N coated cemented carbide tools on the cutting temperature were analyzed. Firstly, the microstructures of PVD Ti_0.41Al_0.59N and Ti_0.55Al_0.45N coatings were inspected. The increase of Al concentration x enhanced the crystallinity of PVD Ti_1−xAl_xN coatings without epitaxy growth of TiAlN crystals. Secondly, the mechanical and thermo-physical properties of PVD Ti_0.41Al_0.59N and Ti_0.55Al_0.45N coated tools were analyzed. The pinning effects of coating increased with the increasing of Al concentration x, which can decrease the friction coefficient between the PVD Ti_1−xAl_xN coated cemented carbide tools and the Inconel 718 material. The coating hardness and thermal conductivity of Ti_1−xAl_xN coatings increased with the increase of Al concentration x. Thirdly, the influences of PVD Ti_1−xAl_xN coated tools on the cutting temperature in turning Inconel 718 were analyzed by mathematical analysis modelling and Lagrange simulation methods. Compared with the uncoated tools, PVD Ti_0.41Al_0.59N coated tools decreased the heat generation as well as the tool temperature to reduce the thermal stress generated within the tools. Lastly, the influences of Ti_1−xAl_xN coatings on surface morphologies of the tool rake faces were analyzed. The conclusions can reveal the influences of PVD Ti_1−xAl_xN coatings on cutting temperature, which can provide guidance in the proper choice of Al concentration x for PVD Ti_1−xAl_xN coated tools in turning Inconel 718.

Effect of coring conditions on temperature rise in bone

Coring is a surgical procedure in bone biopsy retrieval and dental/orthopaedic procedures, which may cause thermal damage to bone tissues adjacent to the coring zone. This study was performed to determine the temperature rise in bone by coring using a semi-empirical thermocouple approach. Concurrently, a custom-made dynamometer was used to measure the cutting and thrust forces during coring bovine cortical bone samples. The experimental results indicated that the cutting force, cutting speed, and depth of cut significantly affect the temperature rise in the cutting zone during coring process. In addition, acute temperature rises in the cutting zone occurred when the cutting speed exceeded threshold levels. The limited capacity of heat dissipation during coring is most likely responsible for such a sharp temperature rise with increasing cutting speed. Moreover, it was observed that the maximum size of potential thermal damage zone could reach to 3.0 mm in depth from the surface of the coring hole, assuming that thermal damage would occur when the temperature is greater than 47°C. Thus, proper cutting conditions need to be selected to avoid the potential thermal damage to bone during the coring procedures.