Search Results (21)

This study investigates the effect of ultrasonic vibration applied in the cutting speed direction on surface quality during face turning of C45 steel. The experiments were performed using an ultrasonic generator operating at a frequency of 20 kHz with an amplitude of approximately 10 µm. The cutting parameters used in the experiments included spindle speeds of 700, 1100, and 1300 rpm, feed rates of 0.1 and 0.15 mm/rev, while the depth of cut was fixed at 0.2 mm. Surface quality was evaluated based on the roughness parameters R_a and R_z, as well as surface topography was observed using a Keyence VHX-7000 digital microscope. The results show that ultrasonic-assisted face turning (UAFT) significantly improves surface finish, particularly in the central region of the workpiece where the cutting speed is lower and built-up edge (BUE) formation is more likely. The lowest R_a value recorded was 0.91 µm, representing a 71% reduction compared to conventional turning (CT). Furthermore, at the highest spindle speed (1300 rpm), the standard deviations of both R_a and R_z were minimal, indicating improved surface consistency due to the suppression of BUE by ultrasonic vibration. Topographical observations further confirmed that UAFT generated regular and periodic surface patterns, in contrast to the irregular textures observed in CT. Full article

During the dry machining of 6061 aluminum alloy, cemented carbide tools often suffer from severe wear and built-up edge (BUE) formation, which significantly shortens tool life. Inspired by the non-smooth surface structure of dung beetles, this study proposes an elliptical dimple–groove composite bionic micro-texture, applied to the rake face of cemented carbide tools to enhance their cutting performance. Four types of tools with different surface textures were designed: non-textured (NT), single-groove texture (PT), circular dimple–groove composite texture (AKGC), and elliptical dimple–groove composite texture (TYGC). The cutting performance of these tools was analyzed through three-dimensional finite element simulations using the Deform-3D (version 11.0, Scientific Forming Technologies Corporation, Columbus, OH, USA) software program. The results showed that, compared to the NT tool, the TYGC tool exhibited the best performance, with a reduction in the main cutting force of approximately 30%, decreased tool wear, and significantly improved chip-breaking behavior. Based on the simulation results, a response surface model was constructed to optimize key texture parameters, and the optimal texture configuration was obtained. In addition, a theoretical model was developed to reveal the mechanism by which the micro-texture reduces interfacial friction and temperature rises by shortening the effective contact length. To verify the accuracy of the simulation and theoretical analysis, cutting experiments were further conducted. The experimental results were consistent with the simulation trends, and the TYGC tool demonstrated superior performance in terms of cutting force reduction, smaller adhesion area, and more stable cutting behavior, validating both the simulation model and the proposed texture design. This study provides a theoretical foundation for the structural optimization of bionic micro-textured cutting tools and offers an in-depth exploration of their friction-reducing and wear-resistant mechanisms, showing promising potential for practical engineering applications. Full article

Investigating failure mechanisms in cutting tools used in advanced industries like biomedical and aerospace, which operate under extreme mechanical and chemical conditions, is essential to prevent failures, optimize performance, and minimize financial losses. The diamond-turning process, operating at micrometer-length scales, forms a tightly bonded built-up edge (BUE). The tribochemical interactions between a single-crystal diamond and its deformed chip induce inter-diffusion and contact, rapidly degrading the cutting edge upon BUE fracture. These effects intensify at higher deformation speeds, contributing to the observed rapid wear of diamond tools during d-shell-rich metal machining in industrial settings. In this study, these interactions were studied with niobium (Nb) as the transition metal. Tribochemical effects were observed at low deformation speeds (quasistatic; <1 mm/s), where thermal effects were negligible under in situ conditions inside the FEI /SEM vacuum chamber room. The configuration of the interface region of diamond and transition metals was characterized and analyzed using focused ion beam (FIB) milling and subsequently characterized through transmission electron microscopy (TEM). The corresponding inter-diffusion was examined by elucidating the phase evolution, element concentration profiles, and microstructure evolution via high-resolution TEM/Images equipped with an TEM/EDS system for elemental characterization. Full article

This study aims to optimize the performance of CrN coatings deposited on WC cutting tools for machining Ti6Al4V alloy, where the formation of built-up edge (BUE) is a prevalent and critical issue. In-house CrN coatings were developed using the PVD (Physical Vapor Deposition) process, with variations in deposition parameters including nitrogen gas pressure, bias voltage, and coating thickness. A comprehensive experimental approach encompassing deposition, characterization, and machining performance evaluation was employed to identify the optimal deposition conditions. The results indicated that CrN coatings deposited at a nitrogen gas pressure of 4 Pa, a bias voltage of −50 V, and a thickness of 1.81 µm exhibited superior performance, significantly reducing BUE formation and tool wear. These optimized coatings demonstrated enhanced properties, such as a higher elastic modulus and a lower coefficient of friction, which contributed to improved tool life and machining performance. Comparative studies with commercial CrN coatings revealed that the in-house developed coatings outperformed the commercial variants by approximately 65% in tool life, owing to their superior mechanical properties and reduced friction. This research highlights the potential of tailored CrN coatings for advanced machining applications and emphasizes the importance of optimizing deposition parameters to achieve high-performance tool coatings. Full article

Anti-wear coatings obtained through PVD methods may significantly increase the durability of cutting tools by impacting their wear mechanisms. This study presents and discusses the results of studies on the impact of the thermal conductivity of PVD coatings on the intensity of the built-up edge (BUE) and built-up layer (BUL) formation in Inconel 600 alloy machining processes. The authors determine the microstructure, phase structure, mechanical properties (hardness, Young’s modulus, and adhesion), and thermal conductivity of different PVD coatings selected for the purpose of the study and varying in terms of conductivity—i.e., AlCrTiN and AlCrTiN/BN. Machining processes were carried out under controlled conditions using VBGT160404-M3 cutting inserts with AlCrTiN and AlCrTiN/BN coatings deposited on their surface. The authors prove that the adjustment of the thermal conductivity of PVD coatings to the thermal conductivity of the tool and machined materials can help change the direction of heat flow to cool the cutting zone more effectively. The study results presented in this article show that the deposition of the AlCrTiN/BN coating reduces the friction wear on the tool flank by over 70% and lowers the intensity of BUE and BUL formation processes on the face by 10%, compared to the AlCrTiN coating. Full article

Inconel 718 is a Ni superalloy with superior mechanical properties, even at high temperatures. However, due to its high hardness and low thermal conductivity, it is considered a difficult-to-machine material. This material is widely used in applications that require good dimensional stability, making the milling process the most used in machining this alloy. The wear resulting from this process and the quality of the machined surface are still challenging factors when it comes to Inconel 718. TiAlN-based coating has been used on cutting tools with Yttrium as a doping element to improve the process performance. Based on this, this work evaluated the machined surface integrity and wear resistance of cutting tools coated using Physical Vapor Deposition (PVD) HiPIMS with TiAlYN in the end milling of Inconel 718, varying the process parameters such as cutting speed (v_c), feed per tooth (f_z), and cutting length (L_cut). It was verified that the L_cut is the parameter that exerts the most significant influence since, even at small distances, Inconel 718 already generates high tool wear (TW). Furthermore, the main wear mechanisms were abrasive and adhesive wear, with the development of a built-up edge (BUE) under a125 m/min feed rate (f) and a L_cut = 15 m. Chipping, cracking, and delamination of the coating were also observed, indicating a lack of adhesion between the coating and the substrate, suggesting the need for a good interlayer or the adjustment of the PVD parameters. Full article

The paper presents the microstructural characterization of the chip roots in high-speed steels and ceramic Ti₃SiC₂. The process of chip formation and the obtaining of adequate samples were carried out using the quick-stop method. The tests were carried out during the milling process; the “quick stop” method was carried out in order to obtain samples of the chip roots. This method was developed in-house by the authors. The chip roots were microscopically studied by means of a light microscope (LM) and a scanning electron microscope (SEM). Before the actual analysis, preparation was performed based on the standard metallographic technique. The analysis of the high-speed steels samples showed that, for the used cutting conditions, a discontinuous chip with a built-up edge (BUE) was formed. During the processing of the Ti₃SiC₂ ceramic, a significant difference was manifested in the chip formation process and a powder-like chip was produced. After utilizing a careful cutting process, a chip pattern was observed, from which it is evident that chip breakage during ceramic processing occurs without prior plastic deformation. In addition, the cutting force F_c was also measured during the milling process of the high-speed steels and the ceramic, and it was correlated with the cutting speed, feed per tooth and depth of cut. Full article

The lubrication capacity and penetration ability of the minimum quantity cooling lubrication-based strategy is linked with lubrication specific parameters (oil flow rates and air pressure), cutting conditions, and chip formation. It points out the complex selection involved in the MQCL-assisted strategy to attain optimal machining performance. Lubrication during metal cutting operations is a complex phenomenon, as it is a strong function of the cutting conditions. In addition, it also depends on the physical properties of the lubricant and chemical interactions. Minimum Quantity Lubrication (MQL) has been criticized due to the absence of cooling parts; MQCL is a modified version where a cooling part in the form of sub-zero temperatures is provided. The aim of this paper was to investigate the influence of different lubrication flow parameters under minimum quantity cooling lubrication (MQCL) when machining aeronautic titanium alloy (Ti6Al4V) using Titanium Aluminum Nitride—Physical Vapor Deposition (TiAlN-PVD) coated cutting inserts. The machining experiments on the MQCL system were performed with different levels of oil flow rates (70, 90, and 100 mL/h) and the performance was compared with the conventional dry cutting and flood cooling settings. A generic trend was observed that increasing the oil flow rate from 70—mL/h to 100 h/h improved the surface finish and reduced thermal softening at a low feed of 0.1 mm/rev. The results revealed that many tool-wear mechanisms such as adhesion, micro-abrasion, edge chipping, notch wear, built-up edge (BUE), and built-up layer (BUL) existed. Full article

This study was undertaken to emphasize the influence of Sn and Bi addition on the machinability of Sr-modified, grain-refined, and heat-treated Al–Si B319 and 396 alloys. Drilling and tapping tests were conducted to examine the cutting forces, tool life, tool wear, built-up edge evolution, and chip shape. Microstructures were examined using optical and electron microscopy. Drilling test results show that the B319.2 alloy with 0.15%Sn yields the longest drill life, i.e., twice that of the B319.2 alloy containing 0.5%Bi, and one-and-a-half times that of the B319.2 alloy containing 0.15%Sn + 0.5%Bi. The presence of 0.5%Bi in the B319.2 alloy causes a deterioration of drill life (cf., 1101 holes with 2100 holes drilled in the B319.2 alloy containing 0.15%Sn). The α-Fe phase in the 396 alloy produces the highest number of holes drilled compared with alloys containing sludge or β-Fe. The presence of sludge decreases the drill life by 50%. Built-up edge (BUE) measurements and optical photographs show little change in the BUE width for different numbers of holes except for the B319.2 alloy containing 0.5%Bi, which shows a slightly lower width (0.166 mm) compared with that containing 0.15% Sn (0.184 mm) or 0.15%Sn + 0.5%Bi (0.170 mm). Full article

The machining of Ti6Al4V alloy, especially at low cutting speeds, is associated with strong Built-Up Edge (BUE) formation. The PVD coatings applied on cutting tools to machine such materials must have the necessary combination of properties to address such an underlying wear mechanism. The present work investigates and shows that TiB₂ PVD coating can be designed to have certain mechanical properties and tribological characteristics that improve machining in cases where BUE formation is observed. Three TiB₂ coatings were studied: one low hardness coating and two high hardness coatings with varied coating thicknesses. Wear performances for the various TiB₂ coated carbide tools were evaluated while rough turning Ti6Al4V. Tool wear characteristics were evaluated using tool life studies and the 3D wear volume measurements of the worn surface. Chip morphology analyses were done to assess the in-situ tribological performance of the coatings. The micro-mechanical properties of the coatings were also studied in detail to co-relate with the coatings’ performances. The results obtained show that during the rough turning of Ti6Al4V alloy with intensive BUE formation, the harder TiB₂ coatings performed worse, with coating delamination on the rake surface under operation, whereas the softer version of the coating exhibited significantly better tool life without significant coating failure. Full article

Tool wear phenomena during the machining of titanium alloys are very complex. Severe adhesive interaction at the tool chip interface, especially at low cutting speeds, leads to intensive Built Up Edge (BUE) formation. Additionally, a high cutting temperature causes rapid wear in the carbide inserts due to the low thermal conductivity of titanium alloys. The current research studies the effect of AlTiN and CrN PVD coatings deposited on cutting tools during the rough turning of a Ti6Al4V alloy with severe BUE formation. Tool wear characteristics were evaluated in detail using a Scanning Electron Microscope (SEM) and volumetric wear measurements. Chip morphology analysis was conducted to assess the in situ tribological performance of the coatings. A high temperature–heavy load tribometer that mimics machining conditions was used to analyze the frictional behavior of the coatings. The micromechanical properties of the coatings were also investigated to gain a better understanding of the coating performance. It was demonstrated that the CrN coating possess unique micromechanical properties and tribological adaptive characteristics that minimize BUE formation and significantly improve tool performance during the machining of the Ti6Al4V alloy. Full article

Rapid tool wear and limited tool life are major problems when machining Inconel 718, which still need further attention. Amongst the reported strategies, limited studies have been reported on optimizing initial cutting conditions by means of tool life improvement. Therefore, in this work, the tool wear progress and tool life were investigated by varying the initial conditions in the transition period, which was set at four seconds. The transition point was discovered by previous works by the authors. After the transition point, similar cutting conditions were used as the reference condition. The tool wear morphology and size were recorded and analyzed in each condition. It was revealed that applying a lower cutting speed and feed rate in the transition period led to improved tool life as compared to the reference condition. In other words, the use of optimum levels of cutting parameters in the transition period of the cutting process may enhance tool life at higher cutting time. For instance, initial feed rate (0.15 mm/rev) and cutting speed (25 m/min) led to the improvement in the ultimate tool life by about 67% and 50%, respectively. Besides, applying the lower initial cutting speed, i.e., 25 m/min, increased the tool life by about 50% when the insert reached the maximum flank wear (v_Bmax) of 300 µm in comparison with those at higher initial cutting speeds. This phenomenon may lead to better insight into the effect of the influence of the initial cutting conditions in the transition period on tool life when machining hard-to-cut materials. Moreover, the built-up edge (BUE) was exhibited as the primary wear mode in all cutting conditions. Full article

The relationship between the wear process and the adaptive response of the coated cutting tool to external stimuli is demonstrated in this review paper. The goal of the featured case studies is to achieve control over the behavior of the tool/workpiece tribo-system, using an example of severe tribological conditions present under machining with intensive built-up edge (BUE) formation. The built-ups developed during the machining process are dynamic structures with a dual role. On one hand they exhibit protective functions but, on the other hand, the process of built-up edge formation is similar to an avalanche. Periodical growth and breakage of BUE eventually leads to tooltip failure and catastrophe of the entire tribo-system. The process of BUE formation is governed by the stick–slip phenomenon occurring at the chip/tool interface which is associated with the self-organized critical process (SOC). This process could be potentially brought under control through the engineered adaptive response of the tribo-system, with the goal of reducing the scale and frequency of the occurring avalanches (built-ups). A number of multiscale frictional processes could be used to achieve this task. Such processes are associated with the strongly non-equilibrium process of self-organization during friction (nano-scale tribo-films formation) as well as physical–chemical and mechanical processes that develop on a microscopic scale inside the coating layer and the carbide substrate. Various strategies for achieving control over wear behavior are presented in this paper using specific machining case studies of several hard-to-cut materials such as stainless steels, titanium alloy (TiAl6V4), compacted graphitic iron (CGI), each of which typically undergoes strong built-up edge formation. Various categories of hard coatings deposited by different physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods are applied on cutting tools and the results of their tribological and wear performance studies are presented. Future research trends are outlined as well. Full article

Metal-matrix composites (MMCs) are made of non-metallic reinforcements in metal matrixes, which have excellent hardness, corrosion, and wear resistance. They are also lightweight and may pose a higher strength-to-weight ratio as compared to commercial titanium alloys. One of the MMCs with remarkable mechanical properties are titanium metal matrix composites (Ti-MMCs), which are considered a replacement for super-alloys in many industrial products and industries. Limited machining and machinability studies of Ti-MMCs were reported under different cutting and lubrication conditions. Tool wear morphology and life are among the main machinability attributes with limited attention. Therefore, this study presents the effects of cutting and lubrication conditions on wear morphology in carbide inserts when turning Ti-MMCs. To that end, maximum flank wear (VB) and cutting forces were recorded, and the wear morphologies within the initial period of the cut, as well as the worn condition, were studied under dry and wet conditions. Experimental results denoted that despite the lubrication mode used, abrasion, diffusion, and adhesion mechanisms were the main wear modes observed. Moreover, built-up layer (BUL) and built-up edge (BUE) were the main phenomena observed that increase the tendency of adhesion at higher cutting times. Full article

This study uses the machine vision method to develop an on-machine turning tool insert condition monitoring system for tool condition monitoring in the cutting processes of computer numerical control (CNC) machines. The system can identify four external turning tool insert conditions, namely fracture, built-up edge (BUE), chipping, and flank wear. This study also designs a visual inspection system for the tip of an insert using the surrounding light source and fill-light, which can be mounted on the turning machine tool, to overcome the environmental effect on the captured insert image for subsequent image processing. During image capture, the intensity of the light source changes to ensure that the test insert has appropriate surface and tip features. This study implements outer profile construction, insert status region capture, insert wear region judgment, and calculation to monitor and classify insert conditions. The insert image is then trimmed according to the vertical flank, horizontal blade, and vertical blade lines. The image of the insert-wear region is captured to monitor flank or chipping wear using grayscale value histogram. The amount of wear is calculated using the wear region image as the evaluation index to judge normal wear or over-wear conditions. On-machine insert condition monitoring is tested to confirm that the proposed system can judge insert fracture, BUE, chipping, and wear. The results demonstrate that the standard deviation of the chipping and amount of wear accounts for 0.67% and 0.62%, of the average value, respectively, thus confirming the stability of system operation. Full article