Coated End Mills Research Articles

Anti-friction and wetting behavior of a new polymer composite coating towards aluminium and dry machining of AA2024 alloy by coated end mills

Soft coating materials now find increasing scopes of applications in environment friendly dry machining of difficult materials like aluminium and its alloys. A composite solid lubricant coating (Gr-X), having graphite and polytetrafluoroethylene (PTFE) as principal constituents, has been proposed to serve the purpose of arresting Built UP Edge (BUE) and Built Up Layer (BUL) in dry machining of aluminium. Its performance has been evaluated in depth in comparison to that of MoS2, which is a well-known solid lubricant. The chemical inertness and coefficient of friction of Gr-X were investigated in wettability and pin on disc test respectively. Compared to MoS2, Gr-X exhibited its less chemical affinity and coefficient of friction (especially at humid atmosphere) with aluminium. Further Gr-X was evaluated in end milling of AA2024 under dry environment, which promises green machining. BUE and BUL were completely eliminated by Gr-X coated tool, resulting in good surface finish and lower magnitude of cutting force. Summarily the proposed Gr-X coating can be a good and feasible economic solution in low Material Removal Rate (MRR) regime machining at low to medium range speeds, which also conforms to the norms of sustainability.

High temperature oxidation and cutting performance of AlCrN, TiVN and multilayered AlCrN/TiVN hard coatings

Transition metal nitrides, such as AlCrN and TiVN, have been used as protective hard coatings due to their excellent tribological properties. In this study, nanostructured AlCrN/TiVN multilayered coatings were deposited periodically by cathodic-arc evaporation (CAE). During the coating process of AlCrN/TiVN, TiN was deposited as an interlayer to enhance adhesion strength between the coating and substrate. The cathode current of both AlCr and TiV alloy targets was controlled to produce hard nitride coatings. The multilayered AlCrN/TiVN coatings possessed higher hardness of 38GPa than that of the monolayered AlCrN (35GPa) and TiVN (22GPa) coatings. A ball-on-disc wear test at room temperature was conducted to evaluate the tribological properties and lubricities of the deposited coatings. It exhibited that the lowest wear rate was obtained for the AlCrN/TiVN coating, which was significantly lower than that of the monolayered AlCrN. To evaluate the cutting performance, end milling tests of 7000 series Al alloys of the deposited tools were conducted at high cutting speed. The multilayered AlCrN/TiVN coated end mills showed better tool life as compared to AlCrN because of high resistance to abrasive and adhesive wear. The design of multilayered AlCrN/TiVN hard coatings improves the overall tribological performance and applicability of these coatings in metal cutting by combining the abrasion-resistance and lubricating effect.

Impact of intra-bond orbital hybridization and morphology of diamond coatings on machining performance of coated end mill cutters

The current study analyses machining performance of diamond coated end mills in the light of coating morphology, difference in intra-bond orbital hybridization, wettability and anti-frictional characteristics. Three different classes of diamond coatings, including a new generation nanocrystalline (NCD) coating, were chosen so that they do contain different intensity of sp2 and sp3 hybridisation in CC covalent bonding. The machining experiments were carried out in slot machining mode accomplished by two-fluted endmills and on aluminium and a silicon-free aluminium alloy, AA2024. sp2-rich hydrogenated DLC coating demonstrated outperformance in anti-frictional characteristics over its counter parts when tested against a sliding aluminium disc. The tribological performance of the sp3-rich NCD coating was superior to the sp3-hybridized microcrystalline diamond coating (MCD) but could not excel H-DLC coating. The difference in the hybridization level did not influence wettability towards the molten aluminium. However, the end mills having new generation NCD coating outperformed its counterparts at high speed machining conditions, establishing the supremacy over H-DLC coating, even over the MCD coating. The coating morphology including roughness played the most influencing role in favour of the machining performance, considering the ability to arrest built up layer (BUL) formation and to produce high surface finish of the machined work-surface.

Chip Formation of S790 Hardned Steel under High Speed Dry Milling Condition

In this paper, the chip morphologies and sizes of hardened PM steel S790 (68 HRC) using four types coated end mills (TiAlN TiCrAlN TiSiN and TiAlSiN) under different cutting parameters in dry milling condition were studied. During the process of high speed milling hardened steel S790, the chip morphologies change from continuous strip to sawtooth with the increase of cutting speeds. When cutting speed reaches 100 m/min, obvious shear slip occoured on the top surface of the chips, which are formed by multilayer metal unit piled by shear slip plane segmentation. The bottom of the chips, which squeeze and slid with rake face of end mills, show shiny smooth surface. TiAlSiN and TiSiN coatings are more suitable for high speed milling than TiAlN and TiCrAlN coatings. With the increase of cutting parameters such as cutting speed, feed rate and axial cutting depth, the chips morphology of S790 change from continuous strips to trapezoidal and triangle sawtooth, and the chips trend easy separation.

The Analysis of Tool Wear in Milling CFRP with Different Diamond Coated Tool

Carbon fiber-reinforced plastics (CFRP) are typical difficult-to-machine materials, which is easy to produce many defects such as burrs, dilacerations, layering in milling process. And selecting the appropriate cutting tool has become the key to machining CFRP with high quality and efficiency. In the paper, the machining principle of milling CFRP with new type end mill was analyzed. The diamond coating of general right-hand end mill, cross-flute router and fine-cross-nick router were used to cutting CFRP under the same cutting condition. Through the comparative analysis of the workpiece’s surface quality and tool wear, it concluded that: compared with right-hand diamond coated end mill, cross-flute diamond coated router or fine-cross-nick diamond coated router could effectively suppress the appearance of burrs and dilacerations; abnormal coating peeling appeared in the flank face of right-hand diamond coated end mill, forming the boundary wear, which accelerated wear failure; the flank wear of diamond coated cross-flute router and fine-cross-nick router were both abrasive wear. Due to having more cutting edge than cross-flute router in cutting process, the flank wear of fine-cross-nick router was slower, and the tool life was longer. So it was more suitable for cutting CFRP.

Damage of PVD-Coated Cutting Tools Due to Interrupted Cutting of Ni-Based Superalloys

Ni-based superalloys are typically difficult-to-cut materials. During machining, the cutting forces and temperatures of these superalloys are generally higher than those of other materials. Therefore, the tool life of the coated carbide cutting tools used for superalloy machining is shortened. This study evaluates the damage of the coated end mills during interrupted cutting of alloy 718 and finds the coating properties necessary for improved cutting of Ni-based superalloys. Damage of the PVD-TiN-coated cutting tools was observed by scanning electron microscopy and transmission electron microscopy of the surfaces and cross sections. In addition, friction forces were measured during turning for some coatings, and hardness of the coatings was measured after annealing. Plastic deformation of the coating and crack formation was shown to occur at the coating cross section. In addition, we determined that the major factor for the damage was high friction force between the coating surface and work material at high temperatures. In summary, coatings with stability at high temperatures and low friction forces during machining can reduce the damage of coated cutting tools, thus increasing the tool life.

Milling damage on Carbon Fibre Reinforced Polymer using TiAlN coated End mills

This paper reports on the damage caused by milling Carbon Fibre Reinforced Composite (CFRP) with 2-flute 4 mm-diameter solid carbide end mills, coated with titanium aluminium nitride. The machining parameters considered in work are, rotation speed, feed rate and depth of cut. Experiments were designed based on Box-Behnken design and the experiments conducted on a Mikrotool DT-110 CNC micro machine. A laser tachometer was used to ascertain a rotational speed for conducting any machining trial. Optical microscopy examination reveals minimum delamination value of 4.05 mm at the spindle speed of 25,000 rpm, depth of cut of 50μm and feed rate of 3 mm/min and the maximum delamination value of 5.04 mm at the spindle speed of 35000 rpm, depth of cut of 150μm and feed rate of 9 mm/min A mathematical model relating the milling parameters and delamination has been established.

Microstructure and cutting performance of CrTiAlN coating for high-speed dry milling

Using a closed field unbalanced magnetron sputtering system, the cemented carbide end mills were coated with a CrTiAlN hard coating, which consisted of a Cr adhesive layer, a CrN interlayer and a CrTiAlN top layer. The microstructure and mechanical properties of the coating were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro indentation and scratch test. The cutting performance of the coated end mills were conducted by high-speed dry milling hardened steel (P20, HRC 45). The results indicates that the coating is composed of (Cr, Ti, Al)N columnar grains with nanolayers. The coating exhibits good adhesion to cemented carbide substrate and high microhardness of around 30 GPa. The coated end mills show significant improvement on tool life and much lower cutting force as compared to the uncoated ones. And the related mechanisms were discussed.

Performance evaluation of ultra-fine grain carbide in high-speed milling of Ti-6Al-4V

An ultra-fine grain carbide cutting tool material was fabricated by using Sinter-HIP technique. Four-tooth solid carbide end mills with a 20 mm diameter and a 0.8 mm corner-radius were manufactured and then coated with physical vapor deposition multilayer TiAlN and AlCrN coatings. Cutting performance of coated ultra-fine grain carbide end mills was investigated via high-speed wet milling tests on Ti-6Al-4V alloy with a TiAlN coated fine grain end mill commercially available for comparison. The transient and progressive cutting forces during wet machining were measured and the chip morphologies were analyzed. The results of the milling tests revealed that the TiAlN coated ultra-fine grain solid carbide end mill exhibited longer tool life, smaller progressive cutting forces, and better broken chips than the TiAlN coated fine grain end mill with the same cutting condition. In addition, the multilayer TiAlN coated end mill achieved higher tool wear resistance than the multilayer AlCrN coated end mill. The longer tool life of the new coated ultra-fine grain solid carbide end mill should be attributed to the smaller grain size of the tool substrate material with higher hardness, higher transverse rupture strength, and better thermo-mechanical fatigue properties, as well as higher wear resistance of TiAlN coating.

Tool Life and Flank Wear of Physical Vapour Deposited TiAlN Multilayer Coated Carbide End Mill Inserts when Machining AISI D2 Hardened Steel under Dry Cutting Condition

This study investigates the tool wear of PVD TiAlN multilayer coated end mill inserts when machining AISI D2 hardened steel in dry conditions. The experiment tests consisting three levels of cutting speed, Vc (80, 100, 120 m/min) and three levels of radial depth of cut, ae (3, 4, 5 mm) was used for the study. The PVD TiAlN coated carbide insert performs satisfactory under the conditions tested, as reasonable tool life is recorded. By linking the machining tests and tool life curves, the wear behaviour of the coated insert was described. It is observed that wear of the tool mainly occurred on the flank wear. Tool life decreasing and volume material removal (VMR) increasing as cutting speed and radial depth of cut increased due to higher temperature generated and contact area immerse, respectively. Tool failure modes and wear mechanisms were examined at various cutting parameters. Built-up edge (BUE), groove and micro-chipping were found to be the predominant tool failure modes for cutting tools. The highest volume material removal, VMR attained was 3750 mm3, meanwhile the higest tool life, TL was 9.69 min.The combination of cutting conditions that gave the best response for different components of tool wear, tool life and surface integrity.

Experimental Study of Tool Wear in Milling Multidirectional CFRP Laminates

This study aims to investigate the wear of coated end mills when milling Carbon fiber reinforced polymer (CFRP) composites. Four different types of end mills are used in the milling experiments to identify the influence of tool geometry and material on tool wear. Cutting forces and wear mechanisms of coated mills are also discussed. Through the contrast experiment, diamond coated multitooth router shows the best performance with the smallest cutting force and the least wear extent under the same cutting parameter. The major failure mechanisms of coated tools are breakthrough of coating, coating flaking and abrasive wear of substrate.

Preparation and Experimental Study of the Complex Shape Carbide Diamond Coated Tools

The CVD diamond films have a series of excellent performances, so it has a wide range of applications in the cutting tools, wearable devices, electrochemical electrodes and other fields, and it has a very substantial market prospects. In this study, The diamond films with a layer of uniform and smooth were deposited on the surface of the complex surface YG6 carbide end mill by using the hot filament CVD method, the quality of diamond films was detected by using the scanning electron microscopy and the laser Raman spectrometer. The cutting performances of diamond coated end mill were evaluated from the workpiece surface quality and tool life two aspects by cutting silicon carbide aluminum reinforced composites, and compared with the uncoated carbide tools. The experimental results show that because of the cutting tool was pretreated that make tool surface coarsening, leading the surface quality was machined by diamond coated tools is lower than the carbide cutting tools. However, the coating can protect the tools, increase the wear resistance of the coated tools and make the life of the diamond coated tools increase 3-5 times than the carbide cutting tools.

Micro-Milling of Fully Sintered ZrO<sub>2</sub> Ceramics with Diamond Coated End Mills

This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO2) with CVD diamond coated end mills. The experiments were conducted on a Kern MMP 2522 micro-milling centre. Diamond coated WC micro end mills with stiff geometry, are employed. Effects of cutting parameters on surface quality were investigated by means of a mixed full factorial experimental design. Surface roughness was measured by a Talysurf 120L profilometer. Surface topography was examined using a scanning electron microscope. The results show that a smaller feed rate was apt to result lower surface roughness. With the increase of cutting length, brittle damages were observed in some tests.

Diamond Coated End Mills in Machining Silicon Carbide

Silicon Carbide (SiC) is a type of ceramic that belongs to the class of hard and brittle material. Machining of ceramic materials can result in surface alterations including rough surface, cracks, subsurface damage and residual stresses. Efficient milling of high performance ceramic involves the selection of appropriate operating parameters to maximize the material removal rate (MRR) while maintaining the low surface finish and limiting surface damage. SiC being a ceramic material, its machining poses a real problem due to its low fracture toughness, making it very sensitive to crack. The paper discusses milling of silicon carbide using diamond coated end mill under different machining conditions in order to determine the surface roughness parameter, Rt after the machining processes and to establish a relationship between the machining parameters and response variables. Based on the surface roughness carried out the lowest Rt obtained is 0.46 µm.

High Speed Milling of Silicon Carbide with Diamond Coated End Mills

The primary applications of silicon carbide SiC-based materials, which include include micro-structures, optoelectronic devices, high temperature electronics, radiation hard electronics and high power/high frequency devices to name a few have necessitated the need for machining SiC. The paper presents the outcome of milling of silicon carbide using diamond coated end mill under different machining conditions in order to determine the surface roughness parameter after the machining processes. Relationship between the machining parameters and response variables has been established and a mathematical model has been predicted, the minimum roughness value, Rz being 0.19 µm.

Tool Wear Characters in Micro-Milling of Fully Sintered ZrO<sub>2</sub> Ceramics by Diamond Coated End Mills

This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO2) by diamond coated tools. The experiments were conducted on a Kern MMP 2522 micro-milling centre and WC micro end mills, diamond coated by chemical vapour deposition (CVD) and of stiff geometry were employed as cutting tools. The effects of cutting parameters and milling time on tool wear were investigated. The results revealed that the tool wear characters included diamond coating delamination and wear of substrate WC. Both cutting forces and machined surface quality were affected by tool wear with the progress of milling.

Assessment of machining with uncoated and coated end mills and determining surface topography using 2D fast Fourier transform

This study focuses on establishing a methodology for the surface roughness characterisation of uncoated and nano multilayer coated tools deposited by physical vapor deposition (PVD) managing an evaluation process after comparison of both experimental measurements utilising the stylus profilometer and the digital microscope, and also image processing technique, fast Fourier transform (FFT). The results showed that the surface roughness of coated cutting tool stayed reasonably constant while those of uncoated cutting tool changed drastically. Cutting edge of uncoated cutting tool was worn out during machining (about 2 mm width and 0.5 mm depth) while that of coated cutting tool remained its original shape almost the same after 25 min. The results from image processing agreed with those from roughness measurement technique. It can be concluded that micro/nano scale measurement techniques combined with image processing technique establish an improved evaluation methodology for the surface of the high precision milling tools.

Micro Ball End Milling of Titanium Alloy Using a Tool with a Microstructured Rake Face

Many parts and structures for aerospace engineering, marine engineering, bioengineering, etc. are made of titanium alloy because of its excellent physical, chemical, biological and mechanical properties. These days, bio and medical technologies have developed, so more precise and smaller parts of this alloy are required to be machined. However, end milling of this alloy is not easy though many different types of coated end mills have been developed. In this paper, a micro ball end mill with a microstructured rake face was fabricated using focused iron beam irradiation. Then, the effects of different microstructured rake faces on cutting forces of titanium alloy Ti-6Al-4V were experimentally investigated for better machining conditions of this alloy. As a result, it was found that some particular types of microstructured rake faces reduced the cutting forces effectively.

High-efficiency and High-precision Machining of Difficult-to-machine Materials by PVD Coated Tools (1st Report)

The UBMS (UnBalanced Magnetron Sputtering) method is applied to the coated end mills and some kinds of such tools are used in high-speed milling of SUS304. This coating film is designed to improve lubricating ability rather than heat resistance. TiCN film deposited by UBMS method (U-TiCN) has smooth surface and low coefficient of friction. XPS analysis reveals that the U-TiCN film includes many free carbons rather than carbide phases, and this structure acts as lubricant as well as thermoprotective film. Long tool life and good finished surface quality are obtained with U-TiCN coated end mills than standard commercially available coated end mills in high-speed side milling without coolant. An U-TiCN end mills having a low coefficient of friction suppress adhesion of workpiece material and overlap of chips to the cutting edge.

Microstructure and properties of TiAlSiN coatings prepared by hybrid PVD technology

TiAlSiN coatings with different Si content were prepared by hollow cathode discharge (HCD) and mid-frequency magnetron sputtering (MFMS) hybrid coating deposition technology. The chemical composition, microstructure, mechanical properties of these coatings were systematically investigated by means of energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nanoindentation measurement, scratch and high speed milling hardened steel tests. The coatings prepared by this method showed the structure of crystalline phase was corresponding to that of TiAlN, however, different preferred orientation with addition of Si. Proper content of Si into TiAlN led to increase of microhardness and adhesion. TiAlSiN coated end mill with Si content of 4.78 at.% had the least flank wear, which was improved about 20% milling distance than TiAlN coated end mill.