Uncoated Tools Research Articles

Dimensional Accuracy After Precision Milling of Magnesium Alloys Using Coated and Uncoated Cutting Tools

Magnesium alloys are an important group of materials that are used in many industries, primarily due to their low weight. Constantly increasing quality requirements make it necessary to improve the accuracy of manufactured products. In this study, the precision milling process for AZ91D and AZ31B magnesium alloys was investigated, and the results obtained with uncoated and TiB2-coated end mills were compared. The impact of variable cutting parameters was also investigated. Specifically, the study focused on the dimensional accuracy of the machined parts. The results showed that even though the dimensional accuracy obtained in milling both magnesium alloys was comparable, it was higher in the case of the AZ31B alloy by up to 22%. The study also demonstrated that the use of the TiB2 coating did not have the desired effect and that higher dimensional accuracy up to 27% was obtained with the uncoated tool.

Enhancing Machining Efficiency: Real-Time Monitoring of Tool Wear with Acoustic Emission and STFT Techniques

Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it can result in poor machining performance. On the other hand, changing the tool too early can lead to unnecessary downtime and increased tooling costs. This makes it critical to closely monitor tool wear and utilize predictive maintenance strategies, such as tool condition monitoring systems, to optimize tool life and maintain machining efficiency. Acoustic emission (AE) is a widely used technique for indirect monitoring. This study investigated the use of Short-Time Fourier Transform (STFT) for real-time monitoring of tool wear in machining AISI 4340 steel using carbide tools. The research aimed to identify specific wear mechanisms, such as abrasive and adhesive ones, through AE signals, providing deeper insights into the temporal evolution of these phenomena. Machining tests were conducted at various cutting speeds, feed rates, and depths of cut, utilizing uncoated and AlCrN-coated carbide tools. AE signals were acquired and analyzed using STFT to isolate wear-related signals from those associated with material deformation. The results showed that STFT effectively identified key frequencies related to wear, such as abrasive between 200 and 1000 kHz and crack propagation between 350 and 550 kHz, enabling a precise characterization of wear mechanisms. Comparative analysis of uncoated and coated tools revealed that AlCrN coatings reduced tool wear extending tool life, demonstrating superior performance in severe cutting conditions. The findings highlight the potential of STFT as a robust tool for monitoring tool wear in machining operations, offering valuable information to optimize tool maintenance and enhance machining efficiency.

Electro-discharge machining using copper-coated additively-manufactured AlSi10Mg electrodes

Customized fabrication of electrodes for electro-discharge machining (EDM) is considered as a useful emerging application of metal additive manufacturing technologies for building complex shaped tools in a short period of time. This approach of producing electrodes not only effectively addresses the design flexibility and complexity issues of the tools but also enables the use of various materials so as to ingrain the desired properties in them. The current study explores the production of laser powder bed fusion (LPBF) AlSi10Mg tools for machining of titanium alloy. Moreover, it explicitly assesses the machining performance of additively manufactured electrodes when the tools are subjected to a thin layer of copper coating. Three types of acidic baths are used for electroless coating of tools. The machining performance of the tools in terms of material removal rate, tool wear rate, surface crack density, surface roughness, white layer thickness, and microhardness of the white layer is compared for different electroless copper coating processes. It is observed that the coated tools significantly enhance material removal rate; however, uncoated LPBF tools exhibit superior surface morphology and surface roughness.

Wear Behavior of TiAlN/DLC Coating on Tools in Milling Copper–Beryllium Alloy AMPCOLOY® 83

In recent years, the exponential growth of the machining industry and its needs has driven the development of new manufacturing technologies, more advanced cutting tool types, and new types of coatings to extend tool lifespan. New coating solutions have been studied and implemented for machining tools, which provide a low friction coefficient and lubrication, thus increasing tool lifespan. Following this line of reasoning, it is relevant to develop scientific work aimed at studying the behavior of cutting tools coated with thin films that promote low friction and high lubrication, as is the case with DLC (diamond-like carbon) coatings. These coatings promote good resistance to oxidation and allow high machining speeds, properties also exhibited by TiAlN (titanium aluminum nitride) coatings. In fact, there is a gap in the literature studying the performance of cemented carbide tools provided with multilayered coatings in milling operations of Cu–Be alloys, commonly used in inserts of plastic injection molds. This study’s objective was to investigate the effect of a multilayer coating (TiAlN/DLC) on end-milling tools to analyze their cutting performance when milling a Cu–Be alloy known commercially as AMPCOLOY®83. The quality of the machined surface was evaluated, and the wear of the cutting tool was studied. A comparative analysis of milling parameters with respect to their effect on the condition of the surface after machining and the resulting wear on the tools, using coated and uncoated tools and different machining parameters, allowed us to verify a better quality of the machined surface and wear quantified in approximately half when used coated tools.

Machinability Performance of Single Coated and Multicoated Carbide Tools During Turning Ti6Al4V Alloy

AbstractThis paper presents the machinability performance of uncoated, single-coated, and multicoated carbide tools during turning of Grade 5 (Ti6Al4V) Titanium alloy, which is challenging to machine due to its distinctive material properties. Coated tools with single-coated Titanium Aluminium Nitride (TiAlN) and multi-coated layer of Titanium Aluminium Nitride with Aluminium Chromium Nitride (TiAlN + AlCrN) coated inserts were utilized to assess surface roughness (Ra), tool wear rate (R), and chip morphologies under various cutting conditions using dry machining. Analysis of the used tools revealed that coated tools exhibited improved tool life and surface quality compared to uncoated tools across all cutting conditions. Multi-coated tools of TiAlN + AlCrN demonstrated a tool life increase of up to 15% compared to uncoated and single-coated tools, with surface roughness improvements ranging from 30 to 45% depending on cutting speed. Chip morphology analysis indicated an increase in the chip reduction coefficient with higher cutting speeds for all tool types. Coated tools exhibited the lowest chip-reduction coefficient due to the presence of TiAlN and AlCrN coatings, which control the tool chip contact length. Conversely, uncoated chip morphology resulted in larger chip thickness values compared to coated tools, particularly at cutting speeds above 100 m/min, attributed to poor heat dissipation and chemical reactions at the tool chip interface. Energy dispersive X-ray scanning electron microscopy (SEM/EDXS) analysis of worn uncoated inserts revealed a higher tendency towards Titanium adhesion compared to coated tools. The proposed multi-layer coatings of (TiAlN + AlCrN) used for dry machining proved highly beneficial for achieving economic machining objectives and may reduce the need for lubrication when processing Ti6Al4V alloys.

Investigations on laser-assisted turning of IN625 alloy with hot hardness approach using uncoated and CrAlSiN coated WC tools

This paper presents an investigation into the effect of laser-assisted turning of the IN625 superalloy using uncoated and CrAlSiN nanocomposite-coated tungsten carbide tools. A hot hardness test was conducted for IN625 material, which showed there was a pronounced softening of the material above 850 °C. This exercise guided the choice of laser power for the subsequent laser-assisted turning experiments. The cutting forces (radial/thrust, Fx; axial/feed, Fy; and tangential/cutting, Fz), maximum flank wear (VBBmax), and surface roughness ( Ra) were measured and analyzed for the planned experiments. The results demonstrated that at 2500 W laser power, a 9%, 70%, and 59% reduction of cutting forces for uncoated tools, and a 31%, 77%, and 69% reduction for CrAlSiN coated tools were observed in the Fx, Fy, and Fz directions respectively. At 2250 W laser power, the uncoated tools exhibited a 33% (433–289 µm) reduction in VBBmax and a 28% (1.8–1.3 µm) reduction in Ra. The CrAlSiN-coated tools, at 2500 W laser power, showed even more significant improvements, with reductions of 46% (365–232 µm) in VBBmax and 56% (1.4–0.8 µm) in Ra. The results underline the improved performance of laser-assisted turning for cutting-force and tool-wear reduction and improved surface finish with CrAlSiN-coated tools. This paper presents the potential of laser-assisted machining as a viable method for machining difficult-to-machine materials like IN625, which offers enormous manufacturing productivity and tool life benefits.

Effect of V concentration in TiSiN monolayer coating on chip formation mechanism and chip sliding velocity during dry turning of Ti–6Al–4V alloy

The current study examines how the self-lubricating characteristics of the novel TiSiVN coating affect the chip formation process and chip sliding velocity during the dry turning of Ti6Al4V titanium alloy. The serration bands tend to straighten at a cutting speed of 125 m/min, which is the main cause of the chips being straightened without tangling for both coated tools. TiSiVN coated tool accounts for higher chip sliding velocity due to the generation of lubricious phases, whereas the higher VS for uncoated tool indicates high tool wear at the highest cutting speed of 125 m/min. Further, r and θn tend to have an inverse relationship with VS, with 125 m/min cutting speed remaining an exception due to severe changes in tool wear dynamics. The reduction of friction helped to lower the localized strain along the shear bands and the effective stress at the beginning of the formation of the serrated tooth.

Effects of TiAlN Coating Thickness on Machined Surface Roughness, Surface Residual Stresses, and Fatigue Life in Turning Inconel 718

The surface roughness and surface residual stresses are affected by the coating thickness of physical vapor deposition (PVD) TiAlN tools, which could alter the service performance of machined components. However, the relationships among the tool coating thickness, the machined surface roughness, the surface residual stress, and the fatigue life are still not sufficiently illustrated. In this research, PVD TiAlN coatings with several thicknesses of 1.6 μm, 2 μm, 2.5 μm, and 3 μm were deposited on carbide tools. Turning experiments using Inconel 718 were conducted with uncoated and various TiAlN tools under flood cooling conditions. The surface roughness could be improved with the selection of thin PVD TiAlN coating thicknesses of 1.6 μm and 2 μm compared to that of uncoated tools. The tensile residual stresses at the machined surface in the directions of cutting speed and feed rate linearly decreased by 148.67% and exponentially decreased by 92.24% when the TiAlN coating thickness was increased from 0 μm to 3 μm. The values of the low-cycle fatigue life of machined Inconel 718 linearly increased by 15.60% with the increase in TiAlN coating thickness from 0 μm to 3 μm, which was mainly due to the improvement of surface residual stresses. The results could provide guidance for the selection of suitable TiAlN coating thicknesses for wet machining Inconel 718 based on the part service conditions.

Greybox-Modelle in der Zerspanung

Abstract Compared to uncoated tools, coated tools offer a longer tool life. However, it is difficult to predict the wear of coated tools using only empirical methods. The combination of deterministic whitebox models and data-driven blackbox models to greybox models can enable a prediction of the wear condition. Therefore, this article presents a concept for the application of greybox models for wear prediction.

Influence of droplet-free ta-C coatings and lubrication conditions on tribological performance and mechanical characteristics of WC−Co

Cemented carbide (WC−Co) tools suffer from surface abrasion, limiting their performance. This study explores droplet-free tetrahedral amorphous carbon (ta-C) coatings deposited via arc ion plating as a solution. The coatings possess a dense, sp3-rich structure, leading to a remarkable hardness of 60 GPa compared to 37 GPa of WC−Co, and strong adhesion with a critical scratch load of 41 N. Tribological tests confirm their effectiveness. Dry sliding tests show reduced wear and lower CoF (0.123) compared to uncoated tools (0.159). Notably, water-soluble lubricants yielded the best performance (lowest CoF: 0.092, superior wear resistance), while water and mineral oil also improved performance.

Machining of Ni-based superalloys using CAPVD coated carbide tools

The ever-increasing demand for cost-effective machining of Ni (Nickel) based superalloys has made it necessary to explore nanocomposite coatings as a potential surface engineering solution. The present study aims to investigate the variation in machining performance of new-generation hard wear-resistant coatings in milling of IN 718 (Inconel 718), IN 625 (Inconel 625), and IN 617 (Inconel 617). TiAlSiN and CrAlSiN coatings were grown in-house over tungsten carbide (WC) milling inserts through the cathodic-arc PVD route. The TiAlSiN coating improved the tool life by 80 % and 60 % in the case of IN 718 and IN 625, respectively. However, in the case of IN 617, the TiAlSiN-coated tool could not even reach the uncoated tool life. The CrAlSiN coating, on the other hand, improved the tool life by more than 200 % in the milling of IN 617. Tool-chipping was the dominant failure mode among all observed, which included flank wear and workpiece adhesion. The repeated adhesion and removal of the workpiece layer from the tool surface was a major cause of tool failure. The coating layer delayed the initiation of the chipping and prolonged the flank-wear-dominated machining time, resulting in improved tool life. The wear resistance of coatings in machining different workpiece materials was greatly influenced by the relative affinity of constituting elements of workpieces for employed coatings. The machining chips exhibited shear bands and saw-tooth (serrated/segmented) morphology in almost all cases. The degree of segmentation showed a direct correlation with tool life. The present work helps identify the optimum coating and machining conditions for three different grades of Ni-based superalloys. Additionally, the underlying mechanisms were analyzed and discussed with scientific observations.

Investigation of tool wear and energy consumption in machining Ti6Al4V alloy with uncoated tools

This research studies the energy consumption and wear mechanism of carbide cutting tools in dry machining of Ti6Al4V alloy. In the first phase of experiments, full factorial design experiments were employed to study the tool wear rate (R) and specific cutting energy (SCE) with respect to the machining conditions (cutting speed and feed rate). Results showed that machining responses such as tool wear and energy consumption are affected by cutting conditions, thus requiring investigation to understand the wear mechanisms. Therefore, in the second phase, additional experiments were performed to investigate the tool-workpiece interactions at the cutting conditions reported to have low, moderate, and high tool wear. It was revealed that strong adhesion and material transfer between the tool and workpiece caused high wear. Electron dispersive X-ray spectroscopy (EDX) analysis of worn tools showed that the transfer of tungsten (W) and cobalt (Co) to the workpiece and titanium to the tool surface is the primary cause of tool deterioration. As a result, diffusion and dissolution have degraded cutting performance and weakened the tool edge, leading to rapid wear. Furthermore, worn tools resulted in relatively higher energy consumption per unit volume of material removed at the tooltip. The degradation of cutting performance and weakening of the tool edge results in rapid wear and higher energy consumption. The study suggests that minimizing tool wear is crucial for energy reduction, improved sustainability, and cleaner production goals in dry machining of titanium-based alloys.

Internally cooled tools as an innovative solution for sustainable machining: Temperature investigation using Inconel 718 superalloy

Machining is a process that involves intense heat generation at localized points within the tool-chip interface. This leads to elevated temperatures, which can be detrimental to cutting tools. This issue becomes even more crucial when dealing with superalloys like Inconel 718, as they exhibit high shear strength and good creep resistance. Consequently, a significant amount of energy is expended, increasing the cutting temperature. Until now, the primary technique employed to address this issue has been using Cutting Fluids (CFs). In machining, a portion of costs is attributed to fluid handling. It also contains harmful elements that can pose health risks, potentially leading to conditions such as cancer. Moreover, the toxic components can contribute to environmental degradation when improperly disposed of. Therefore, this study proposes an innovative cooling technique called Internally Cooled Tools (ICTs). The ICTs employ an internally circulating coolant fluid through closed cooling channels within the cutting tools, eliminating fluid dispersion into the atmosphere. The main objective was to compare the performance of ICTs in controlling the tool-chip interface temperature during Inconel 718 turning using hard metal tools. For this purpose, a complete factorial experimental design (25) was utilized, with the response variable being the temperature measured by the tool-work thermocouples technique. Beyond that, a sustainable assessment was performed using the Pugh Matrix method. Many key sustainable factors were evaluated related to three atmospheres, cutting fluids in abundance – CFA, dry machining, and ICT. The data base used was a depth literature investigation together with results found in this work. The main findings of this entire work demonstrated that an increase in cutting parameters corresponded to an increase in temperature, as anticipated. TiNAl coating reduced the temperature by up to 10% compared to uncoated tools. Similarly, applying ICTs led to temperature reductions of up to 17% compared to dry machining conditions. The Pugh Matrix made considering 12 factors showed that ICT (14 points) was the most sustainable lubri-cooling method in comparison to CFA (3) and DM (5). Ultimately, ICTs showed to be a promising eco-friendly method. It outperformed conventional methods, showcasing a remarkable heat dissipation capacity. As a result, further studies are warranted to delve deeper into this promising approach.

Characterization of friction behavior under cryogenic conditions: Ti–6Al–4V

Friction phenomena at the chip/tool/workpiece interfaces during machining of material impacts significantly the cutting process. In this article, the effect of friction conditions (dry, emulsion, cryogenic) on the tribological performance of uncoated tungsten carbide tools is investigated when machining titanium alloy Ti–6Al–4V. Friction tests were conducted to analyze the impact of sliding speed and cooling on the evolution of the friction coefficient. To determine the real friction coefficient (adhesive friction coefficient), a numerical simulation using the Lagrangian method was employed. After a comparative study of various simulation methods (“Lagrangian”, “CEL”, and “ALE”), the Lagrangian method was identified as the most relevant. The obtained results reveal that an increase of sliding velocity significantly influences the friction coefficient. Additionally, the application of cryogenic fluid (LN2) reduces the friction coefficient compared to both dry and emulsion-based friction. Adhesion phenomena play a crucial role in the nature of the contact, especially at high sliding velocities.

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.

Evaluation of the performance of DLC Coatings (ta-C) of WC-Co tools while machining Al7075 alloy

This study investigates the performance of DLC-coated 3-flute Ø 12 mm WC-Co (10%) end mills in the high-speed machining (226 m/min) of Al7075 Aluminum alloy, with high-pressure (20 bar) cooling applied in all tests focused on the cutting zone. Rolled blocks with dimensions of 150 × 350 × 150 mm were used as workpiece material. Slot milling was preferred as a test method for machining tests. Each end mill machined 757 slots with a length of 350 mm at a depth of 3 mm, and a total volume of 9150 cm3 was removed with each tool. In total, three groups of endmills were tested. A1 is a specially designed endmill for aluminum machining and was tested in an uncoated state, while A2 has the exact same geometry as A1 and was coated with tetrahedral amorphous carbon (ta-C), which is a form of Diamond-Like Carbon (DLC) coating. Finally, the A3 endmill was tested as an industrial comparative designed for aluminum machining, which was also ta-C coated. Performance tests have shown that ta-C coating significantly prevented the formation of the built-up edge. In addition, it reduced the average bending moment on the tool by 20%–25% by acting as a lubricant. It has been observed that DLC coating reduces tool wear. It was determined that flank wear was reduced by 28% and rake wear by approximately 58% in the A2 tool compared to the uncoated tool. The DLC-coated tools also provided smaller chips and improved chip control.

An assessment of machining performance of CAPVD-coated carbide tools in face milling of Ti-6Al-4V

The present study aims to extend the life of tungsten carbide (WC) cutting tools utilized in face milling operations of Ti-6Al-4V by applying hard protective coatings developed using the cathodic-arc physical vapor deposition (CAPVD) technique. Box-Behnken design with 15 experimental runs and response surface methodology were used to mathematically model the relationships between input parameters and output responses to determine the optimal cutting parameters resulting in maximum material removal rate and minimum tool wear. Additionally, the performance of uncoated and coated carbide tools was assessed under dry and wet conditions to identify the best machining conditions. Intriguingly, the tool life of an uncoated WC tool in dry conditions was up to threefold more than that in wet conditions. The tool life of the coated tools was 33% to 166% longer than that of their uncoated counterparts. An analysis of their performance revealed an inverse relationship between the amount of Al in the coating and the tool life. The results from sliding wear tests suggest that Al-deficient coatings have a low coefficient of friction. This study sheds light on the effectiveness of CAPVD-coated carbide tools for improving the tool life during face milling of Ti-6Al-4V.

Influence of V concentration in TiAlSiVN coating on self-lubrication, friction and tool wear during two-pass dry turning of austenitic steel 316 L

The present work investigates the performance of TiAlSiVN coating with 5 and 11 at% of V concentration deposited on the Al2O3/SiC cutting tools during dry turning of austenitic 316 L stainless steel. The maximum flank wear reduction compared to the uncoated tool for coated tools with 11% and 5% V concentration was 85% and 67%, respectively. The Raman analysis indicated the formation of V2O5 in the cutting zone, which helps to reduce friction and machining forces for the coated tools. Overall, the presence of higher V content (11 at%) enhances the self-lubrication behaviour of the TiAlSiVN coating, accounting to lower fluctuations in cutting forces, superior surface finish, and lower flank wear when compared to the TiAlSiV5N coated and uncoated cutting tools.

Tool life assessment of high strength cast iron alloys in dry face milling operations

The advancement in cast iron alloy properties has led to more efficient materials, especially in the automotive industry. However, this progress has also increased the demand for more durable tools with greater resistance to cutting operations. Conducting an in-depth investigation into the impact of these materials on tool lifespan is crucial, as it directly affects productivity. The main objective of this study was to analyze the lifespan of uncoated cemented carbide tools during milling operations using four high-strength cast iron alloys under various dry cutting conditions. A full factorial Design of Experiment (DoE) (23) was employed. The input variables included cutting speed (vc) of 230 and 350 m/min, tool feed (fz) of 0.1 and 0.2 mm/tooth, and materials, namely cast irons (FC 250, FC 300(Mo), FC300(Mo+RG), and FV 450). Additionally, material tests were conducted on billets without holes to simulate mild cutting conditions and with holes for more severe machining conditions. The established machining operation was face milling without cutting fluid, with the axial depth of cut (ap) and radial depth of cut (ae) maintained constant at 1 mm and 60 mm, respectively. The results showed that FV 450 had the shortest tool life, as expected for the hardest and resistant material, with a maximum lifetime difference of 83 % less when compared to FC 250, the softest one that had the longest tool lifespan. The introduction of holes also significantly reduced the overall tool life by about 57 %. The findings highlight the importance of factors such as cutting speed, feed per tooth, material composition, impact, and workpiece surface quality, which significantly influence tool performance.

A comparative study of hole integrity performance in composite‐metal stacks using coated and uncoated tungsten carbide drill bits

AbstractThis study aims to develop tetrahedral amorphous carbon nanocomposite layer coated tungsten carbide drill bits for single shot drilling of composite metal stack. Different coatings were tested for hole integrity performance compared to an uncoated tool and the results were validated using process capability six‐pack analysis. The drilling process employed a 4.85 mm twist drill with a feed rate of 0.05 mm/rev and spindle speed of 2600 rev/min. The experimental results indicate that, all the coated tools produce H9 tolerance holes while uncoated tool produced H7 tolerance holes with 18 % to 35 % better results. But statistical results show that all the tools including uncoated tool require improvement to stay within the control limits. The hole circularity error obtained by all the tools were below 24 μm in both the panels and is supported by the statistical results as well. The uncoated tool exhibited 17.91 % better surface roughness in aluminium panel compared to coated tools, while coated tools produced 17.2 % to 22.3 % better surface roughness in composite panel. Statistical results suggested that, improvement is necessary when drilling aluminium panel by all the tools while dopant added coated tools produce better results in composite panel.