Adhesion Of Work Material Research Articles

Performance Evaluation of Micro-Textured Inserts Coupled With Solid Lubricants During the Sustainable Dry Machining of Inconel 825

Abstract In this research work, the turning of Inconel 825 has been carried out using uncoated and coated laser-textured hard tungsten carbide (WC) cutting inserts. The efficacy of uncoated textured inserts has been tried to improve by impregnating them with micro-sized MoS2 and nano-TiC powder paste. The results of coated and uncoated textured inserts have been compared with the plain uncoated tungsten carbide insert. The use of solid lubricant-impregnated textured tools and coated textured tools has significantly reduced the cutting forces and chip–tool interface friction as compared to plain and normal textured tools. Upon the SEM analysis, high adhesion over the rake face of the plain tool has been observed. The excessive adhesion over the rake surface has been observed over the normal textured tool due to the derivative cutting phenomena. The use of MoS2 and nano-TiC-impregnated textured tools has significantly reduced the material adhesion over the rake surface by eliminating the derivative cutting effect. The use of AlTiSiN-coated textured tools has also restricted the extent of work material adhesion over the rake surface of the cutting insert.

Analysis of Tool Wear and Chip Morphology during Turning of AZ31B Magnesium Alloy under Dry Environment

The present research investigated the turning of AZ31B magnesium alloy in a dry environment using carbide tool inserts coated with tungsten carbonitride (TiCn) and thin alumina (Al2O3). A Box–Behnken design based on fifteen experiments showed a proportional increasing trend of flank wear with all three machining parameters, i.e., cutting speed, feed rate, and depth of cut. The most influential parameter is the cutting speed. A maximum flank wear of 299.34 µm due to excessive adhesion of work material on the tool face was observed at a high cutting speed. Machining at low speed resulted in a significant reduction in tool wear due to less chipping. The tool wear and chip morphology study confirmed the results.

Performance of carbide end mills coated with new generation nano-composite TiAlSiN in machining of austenitic stainless steel under near-dry (MQL) and flood cooling conditions

In the present study, a new generation nano-composite TiAlSiN coating has been deposited on 2-fluted carbide end mills using High Power Impulse Magnetron Sputtering (HiPIMS) in quadra-cathode target configuration. A highly smooth coating of about 3 μm thickness was realized and coated tools were subject to high-speed milling of austenitic stainless steel, which is otherwise known to cause severe diffusive wear on uncoated carbide tools. The effectiveness of TiAlSiN coating has been investigated on austenitic stainless steel under dry, wet (flood, 25 l/h), and near-dry (MQL, 250 ml/h) conditions. TiAlSiN coated tools experienced severe diffusive adhesion of work material on its cutting edge during dry machining. The near-dry approach with a cutting fluid consumption rate of only 250 ml/h was found to be a more effective, and greener approach. There was no sign of delamination of the coating under dry, flood, and near-dry environments. A maximum of 20 % reduction in cutting force and 45 % reduction in roughness (Ra) have been recorded in a near-dry environment compared to a flood environment. Performance of the HiPIMS deposited TiAlSiN coated tools have also been compared with that of commercial TiAlN and commercial TiAlSiN tools (deposited by DC Magnetron Sputtering) and found to be potentially more effective in milling of SS304 steel.

Effect of cutting fluids applied in MQCL mode on machinability of Ti-6Al-4V

This paper experimentally investigates the role of minimum quantity cooling-lubrication (MQCL) with soluble oil, aqueous alumina and hBN nanofluids in turning of Ti-6Al-4 V. The effect of various machining environments has been studied on different machinability characteristics like all the three components of cutting forces, state of effective lubrication at the chip-tool interface, different tool wear parameters and adhesion of work material on the rake surface. The concept of cumulative machinability index has been used to analyze the role of machining environments. Soluble oil when applied in MQCL mode provided the best performance due to a much better state of effective lubrication at the chip-tool interface. Flood cooling with the same soluble oil could not provide comparable performance mainly due to its poor reachability at the chip-tool interface. Aqueous nanofluids also could not compete with soluble oil applied in MQCL mode mainly due to the intimate nature of contact and high cutting temperature at the chip-tool interface in turning of Ti-alloys.

FEM simulation of micromilling of CuZn37 brass considering tool run-out

Micro-milling process of CuZn37 brass is considered important due to applications in tool production for micro replication technology. Variation in material properties, work material adhesion to tool surfaces, burr formation, and tool wear result in loss of productivity. Chip shapes together with localized temperature, plastic strain, and cutting forces during micro milling process can be predicted using Finite Element (FE) modelling and simulation. However, tool-workpiece engagement suffers from tool run-out affecting process performance in surface generation. This work provides experimental investigations on effects of tool run-out as well as process insight obtained from 3D FE simulations with and without considering tool run-out. Scanning electron microscope (SEM) observation of the 3D chip shapes demonstrates ductile deformed surfaces together with localized serration behavior. FE simulations are utilized to investigate the effects of cutting speed on cutting forces. Cutting force and chip morphology results from simulations are compared with force measurements, and actual chip morphology acquired by SEM revealing reasonable agreements.

Thermal, rheological, wettability and hard machining performance of MoS2 and CaF2 based minimum quantity hybrid nano-green cutting fluids

Minimum quantity cutting fluids (MQCF) is an alternative for dry machining and flood cooling. However, use of MQCF is limited to mild machining conditions due to high heat generation during machining of hard materials. The applicability of MQCF can be extended in aggressive machining conditions by using vegetable-based green cutting fluids (GCF) with solid lubricant nanoparticles as potential additives. In the present study, hybrid nano-green cutting fluids (HN-GCFs) were prepared by mixing different volume concentration of calcium fluoride (CaF2) and molybdenum disulphide (MoS2) solid lubricants in indigenously developed vegetable based GCF. Dispersion stability, thermal conductivity, specific volumetric heat capacity, viscosities and wetting angle of HN-GCFs were measured. In-house fabricated MQCF setup is used to apply minimum HN-GCF across the machining region. Later, the experimentally optimised concentration of both CaF2 and MoS2 based HN-GCFs were selected for machining experiments using MQCF setup. Hard machining experiments were carried out using four different cutting fluids: commercial mineral oil (MO), GCF, 0.3% concentration of CaF2 based HN-GCF (HN-GCF-0.3C) and 0.3% concentration of MoS2 based HN-GCF (HN-GCF-0.3 M). Comparative tool wear, workpiece material adhesion and workpiece surface morphology were also investigated. Results show that 0.3% concentration of HN-GCF-0.3M performs better concerning tool-workpiece interface coefficient of friction, cutting force, feed force, and workpiece surface roughness compared to other cutting fluids. During machining with HN-GCF-0.3M, cutting tool experiences 17% and 28% lower cutting as well as feed force, respectively as compared with machining using MO. Also, 11% reduction in tool-chip interface coefficient of friction was observed during machining using HN-GCF-0.3M, and it also produces 37% better workpiece surface finish. Elemental analysis of cutting tool confirms less work material adhesion on the cutting tool rake face using HN-GCF-0.3M.

Finite element simulation of high speed micro milling in the presence of tool run-out with experimental validations

Micro milling process of CuZn37 brass is considered important due to applications in tool production for micro moulding and micro replication technology. The variations in material properties, work material adhesion to tool surfaces, burr formation, and tool wear result in loss of productivity. The deformed chip shapes together with localized temperature, plastic strain, and cutting forces during micro milling process can be predicted using finite element (FE) modeling and simulation. However, tool-workpiece engagement suffers from tool run-out affecting process performance in surface generation. This work provides experimental investigations on effects of tool run-out as well as process insight obtained from simulation of chip flow, with and without considering tool run-out. Scanning electron microscope (SEM) observation of the 3D chip shapes demonstrates ductile deformed surfaces together with localized serration behavior. FE simulations are utilized to investigate the effects of micro milling operation, cutting speed, and feed rate on forces, chip flow, and shapes. Predicted cutting forces and chip flow results from simulations are compared with force measurements, tool run-out, and chip morphology revealing reasonable agreements.

Effects of micro textured sapphire tool regarding cutting forces in turning operations

In this study, the effects of microscale textures on a sapphire cutting tool were investigated. The texturing of microscale features on a solid surface allowed control of the tribological characteristics of the tool surface. Microscale geometrical characteristics on the rake face of the sapphire tools were obtained through micro-abrasive blasting. Tribological tests and cutting tests on an aluminum alloy workpiece were carried out, and the cutting forces were measured and analyzed. The effect of texture on adhesion of work material was investigated. Results showed that friction was minimized and cutting forces at the tool-chip interface of the textured tool were significantly reduced from those of a conventional tool. It was observed that the adhesion of work material was reduced by applying texture on the tool rake face.

Blend of sharpness and strength on a ball nose endmill geometry for high speed machining of Ti6Al4V

The applications of titanium alloys are increasingly common at marine, aerospace, bio-medical and precision engineering due to its high strength to weight ratio and high temperature-withstanding properties. However, whilst machining the titanium alloys using the solid carbide tools, even with application of high pressure coolant, reduced tool life was widely reported. The generation of high temperatures at the tool–work interface causes adhesion of work material on the cutting edges, and hence, shorter tool life was reported. In order to reduce the high tool–work interface temperature-positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose endmill cutting edges. Despite of careful consideration of tool geometry, after an initial working period, the growth of flank wear accelerates the high cutting forces followed by work material adhesion on the cutting edges. Hence, it is important to blend the strength, sharpness, geometry and surface integrity on the cutting edges so that the ball nose endmill would exhibit an extended tool life. This paper illustrates the effect of ball nose endmill geometry on high speed machining of Ti6Al4V. Three different ball nose endmill geometries were configured, and high speed machining experiments were conducted to study the influence of cutting tool geometry on the metal cutting mechanism of Ti-6Al-4V alloy. The high speed machining results predominantly emphasize the significance of cutting edge features such as K-land, rake angle and cutting edge radius. The ball nose endmills featured with a short negative rake angle of value −5° for 0.05∼0.06 mm, i.e. K-land followed by positive rake angle of value 8°, has produced lower cutting forces signatures for Ti-6Al-4V alloy.

Influence of Minimum Quantity Lubrication on Friction Coefficient and Work-Material Adhesion During Machining of Cast Aluminum With Various Cutting Tool Substrates Made of Polycrystalline Diamond, High Speed Steel, and Carbides

Due to the increasing emphasis on environmental constraints, industry works on how to limit the massive use of lubricants by using the micro-pulverization of oil in machining processes and, especially, in the machining of aluminum alloys for the automotive industry. The success of a machining operation is dependent on a friction coefficient and weak adhesion with the tool-work material interface. This paper aims at identifying the influence of cutting tool substrates (high speed steel (HSS), carbide, polycrystalline diamond (PCD)) and of minimum quantity lubrication (MQL) on the friction coefficient and on adhesion in tribological conditions corresponding to the ones observed in the cutting of aluminum alloys (sliding velocity: 20-1500 m/min). An open ball-on-cylinder tribometer, especially designed to simulate these tribological conditions through Hertz contact, has been used. It has been shown that HSS and carbide substrates lead to large friction coefficients (0.8–1) and substantial adhesion in dry conditions, whereas PCD substrates would lead to lower average friction coefficient values (0.4–0.5) and very limited adhesion, which proves the necessity of using PCD tools in the dry machining of aluminum. It has also been shown that the application of MQL leads to a large decrease of the friction coefficient (0.1–0.2) and eliminates almost all traces of adhesions on pins for any substrates, which shows that MQL is an interesting compromise between dry machining and flood cooling.

Wear characteristic on BAM coated carbide tool in drilling of composite/titanium stack

This paper studied characteristics on a BAM coated carbide, which comes from a ceramic alloy of boron, aluminum, magnesium, etc., in drilling of CFRP and titanium (Ti) stacks. A series of drilling test was performed starting from drilling of CFRP (top) to Ti (bottom) in the stacks using uncoated tungsten carbide (WC) and BAM coated WC. The BAM coating, which is known for one of the hardest and slipperiest materials. In this regard, BAM coating can be used for cutting tool by reducing the adhesion of work material and interfacial friction. Tool surfaces were periodically measured during the drilling tests using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and confocal laser scanning microscope (CLSM) in order to analyze the tool wear evolution and metallurgical changes on the tool surface. From the experiment, it was observed that no major wear occurred on rake surface and center of the tool while flank wear was significant. The wear mechanisms on flank surface were abrasion and titanium adhesion. The abrasion wear took place by the hard carbon fibers in CFRP and the hard inclusions in titanium. On the other hand, the adhesive wear occurred by pulling out the carbide grains when the adhered titanium layers detached from the tool surface. BAM coated carbide tool showed substantially reduced Ti adhesion especially at high cutting speed. In addition, the lower flank wear was observed for BAM coated tool compared with for uncoated carbide tool.

Machining Behaviour of Ti-6Al-4 V and Ti-5553 All0oys in Interrupted Cutting with PVD Coated Cemented carbide

Machining behaviour of Ti-5553, Ti-6Al-4V mill-annealed (MA) and Ti-6Al-4V solution treated and aged (STA) alloys was studied in different interrupted cutting operations using PVD coated cemented carbide tools. Single tooth face milling was employed to study the wear behaviour and tool life of the coated tools that were further inspected using scanning electron microscopy. The results indicated that a poor machinability was observed for Ti-5553 when compared to Ti-6Al-4V (STA) and Ti6Al-4V (MA). This was found to correlate reasonably well with an increase of work material adhesion severity on the cutting tool that resulted in an increased chipping and led to catastrophic tool failure. Series of orthogonal interrupted cutting tests were performed subsequently to investigate the role of work material and cutting data on the chip formation, mechanical loads and frictional conditions at the tool-chip contact. A detailed analysis of the chip segmentation characteristics of the different Ti alloys is provided and the results are employed in different analytical models to assess the shear strain, strain rate and segmentation frequency. Finally, a comparison of Ti-5553 and Ti-6-4 (MA) in interrupted turning is presented where the differences in terms of cutting temperature are discussed.

Grinding Performance of a Grain-Arranged Diamond Wheel against Aluminum Alloys and Ti6Al4V

A grain-arranged diamond wheel was developed and grinding performance of the wheel against aluminum alloys and titanium alloy, Ti6Al4V, has been investigated using various kinds of grinding fluid. Mirror finishing of aluminum alloys was successfully performed without grinding burn when emulsion-type grinding fluid with an extreme-pressure additive was used. When oil base lubricants or a fatty acid was supplied using a MQL supply unit, fine finishing could not be done. Mesh size of the grinding wheel had only a minor effect on surface roughness. When Ti6Al4V was ground by the developed wheel, an adhesion of work material on diamond grains occurred causing the finished surface to deteriorate.

Extraction of flank wear growth models that correlates cutting edge integrity of ball nose end mills while machining titanium

The application of titanium alloys are increasingly seen at aerospace, marine, bio-medical and precision engineering due to its high strength to weight ratio and high temperature properties. However, while machining the titanium alloys using solid carbide tools, even with jet infusion of coolant lower tool life was vividly seen. The high temperatures generated at the tool–work interface causes adhesion of work-material on the cutting edges; hence, shorter tool life was reported. To reduce the high tool–work interface temperature positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose end-mill cutting edges. However, after an initial working period, the growth of flank wear facilitates higher cutting forces followed by work-material adhesion on the cutting edges. Therefore, it is important to blend the strength, sharpness and surface integrity on the cutting edges so that the ball nose end mill would demonstrate an extended tool-life. Presently, validation of tool geometry is very tedious as it requires extensive machining experiments. This paper illustrates a new feature-based ball-nose-end-mill–work interface model with correlations to the material removal mechanisms by which the tool geometry optimization becomes easier. The data are further deployed to develop a multi-sensory feature extraction/correlation model to predict the performance using wavelet analysis and Wagner Ville distribution. Conclusively, this method enables to evaluate the different ball nose end mill geometry and reduces the product development cycle time.

On adhesion of work material in metal forming

The transfer of work material to the tool surface limits the tool life in many forming operations. Using a dedicated load-scanning test equipment with crossed-cylinder geometry, dry forming of austenitic stainless steel was simulated by provoking adhesion to the TiN-coated tool specimen. High-resolution electron microscopy combined with analytical techniques was used to examine the interface between tool and work material. The decisive mechanism for adhesion and transfer of steel to the TiN surface is suggested. The oxide layer on the steel surface, especially the Fe-oxide, initiates the metal transfer. The interfacial oxide acts as a glue between stainless steel and TiN and increases the adhesive forces. Obviously, the adhesion and internal strength of the oxide layer is far stronger than anticipated. It may even be stronger than the bonding to the austenitic steel itself. A consequence of these findings is that the development of galling resistance-forming tool materials and coatings for austenitic stainless steels should not only aim to improve the bulk tool material, but also to reduce the adhesion strength between the tool surface and the oxide layer on the work material.

Influence from Tool Roughness on the Risk of Work Material Adhesion and Transfer

Influence from surface roughness of a forming tool surface on its ability to pick up work material was investigated by laboratory testing. One powder metallurgical tool steel was given different surface roughnesses and tested in sliding contact against one austenitic stainless steel (SS) and one aluminium alloy (Al). Generally, the risk of work material adhesion and transfer increased with the roughness of the tool material. However, SS gave a low friction and very little metal transfer for a tool roughness of the order of the relatively soft SS oxide thickness. The Al alloy, on the other hand, which oxide is much harder than the parent metal, has no critical surface roughness below which adhesive transfer will not occur. The oxide fractures and oxide fragments indent the tool surface increasing the risk of adhesion.

Proper coating selection for improved galling performance of forming tool steel

The aim of the present work was to investigate and compare different hard coatings as to the tendency for work material adhesion and galling properties when applied on forming tool steel and sliding against different work materials. The surface coatings included were PVD deposited TiN, TiB 2, VN, TaC and DLC coatings. They were all applied to cold work tool steel. Tribological evaluation was carried out in a load-scanning test rig, with the normal load being gradually increased during each test from 100 to 1300 N (1–3.5 GPa). The coated steel was tested against austenitic stainless steel and alloys of aluminium and titanium. This investigation clearly indicates that work material adhesion and galling performance of coated forming tool steel greatly depends on the type of work material. In the case of stainless steel, carbon-based coatings provide the best protection against the work material transfer, while forming of aluminium and titanium alloys, requires nitride type coatings, such as TiN.

2601 アルミ合金の高速ミリングにおけるOoW冷却効果(S71-1 高速・高精度加工とエコマシニング(1),S71 高速・高精度加工とエコマシニング)

In high-speed milling of aluminum alloy, flood coolant application has conventionally used to avoid adhesion of work material onto a tool surface. However great effort to reduce use of lubricant has being made to tackle growing environmental problems. Although MQL is one of the methods to reduce use of lubricant greatly, it can not successfully replace conventional flood emulsion because of less cooling ability. Oil-on-water droplet cutting fluid can cover the shortcoming of the MQL because it has large cooling ability. Furthermore, the OoW can reduce cutting force in comparison with that in the both cases of flood coolant and MQL applications. In this study, effect of the cooling ability of the OoW on reduction in cutting force is investigated in aluminum alloy milling. It is suggested that lubricant can effectively serve good performance and then reduce the cutting force only if tool surface can be sufficiently chilled.

Effects of the Addition of Si and Cu on the Chip Breaking under Lathe Machining of Al-1.0 mass%Mg-0.8 mass%Si Alloy

For improving the machinability of aluminum alloys without adding low melting-temperature elements such as Pb or Bi, effects of the addition of Si and Cu, solely or in combination, on the chip breaking were examined for peak-aged (T8) Al-1.0 mass%Mg-0.8 mass%Si alloy (A 6061 alloy) under lathe machining at cutting speeds V = 0.83∼3.33 m/s in dry and wet atmospheres. The magnitude of chip breaking N = (the number of chips) / (100 g of chips) increased with a dcrease in V and with the addition of Si and Si+Cu in both cutting atmospheres. The value of N amounted to ∼22000/100 g, that is ∼6 times larger than that of 6061 alloy and is large enough for practical machining operation, at the smallest V of 0.83m/s in the wet atmosphere where the adhesion of work material on the tool surface scarcely occurred. Such a notable improvement of chip breaking by the combined addition of Si and Cu was ascribed to the existence of large Si particles at which micro-cracks appear and along which they propagate, and also to the solution and precipitation hardening of the matrix which results in the loss of fracture ductility.

Strengthening structures with spray-on fibre-reinforced plastic coatings

In this paper, the performance and the wear mechanisms of coated carbide tools have been investigated when face milling titanium alloy, Ti–6Al–4V. The two tools used were PVD–TiN and CVD–TiCN + Al2O3 coated. Tool life, tool failure modes and wear mechanisms were examined for various cutting conditions. Both tools experienced long tool life at the low cutting speed of 55 m/min and feed of 0.1 mm per tooth. When considering the volume of material removed and tool lives, the CVD coated tools gave a better performance than the PVD coated tools. Excessive chipping at the cutting edge and chipping and/or flaking on the rake face were the dominant failure modes under most cutting conditions. Analysis carried out with the SEM suggests that coating delamination, adhesion of work material, attrition, diffusion, plastic deformation and thermal cracks were the operating wear mechanisms of the coated tools.