High-pressure Coolant Supply Research Articles

Wear resistance enhancement of Inconel 718 via high-speed ultrasonic vibration cutting and associated surface integrity evaluation under high-pressure coolant supply

Machining-induced surface integrity evaluation and functional performance are considered as the most representative problems for evaluating the machining quality of Ni-based superalloys (for example, Inconel 718). Although high-speed ultrasonic vibration cutting (HUVC) has been proved to be effective for improving the machinability of Inconel 718, the surface integrity and its effect on functional performance (for example, wear resistance) are still unclear. By applying scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and white light interferometry (WLI), the surface integrity induced by HUVC and the wear resistance of the machined surface were comprehensively evaluated; the grain refinement, hardness increase, and wear mechanism of the machined surface were thoroughly studied, which were compared with the conventional cutting (CC) process. Compared with the CC process, the HUVC process achieves superior grain refinement, thicker surface plastic deformation layer, lower surface roughness Ra and Rz, higher hardness and compressive residual stress, and thicker hardening layer. The wear rate of the machined surface processed by HUVC is reduced by at most 24.01%. This study shows that the HUVC process can be potentially used to improve the wear resistance, which can effectively achieve grain refinement, surface roughness reduction, and wear resistance improvement while reducing the machining cost and process procedure.

Interrupted cutting of Inconel 718 with AlTiSiN coated cemented carbide tool under high pressure coolant supply

Inconel 718 is one of the most difficult-to-cut materials, with an exceptionally short tool life. In comparison to continuous cutting operations such as turning, the interrupted cutting of Inconel 718 is highly challenging due to the fluctuation in both thermal and mechanical load. In this study, to achieve high performance interrupted cutting of Inconel 718, we focused on a high pressure coolant (HPC) technology and investigated its performance when using an AlTiSiN coated cemented carbide cutting tool, with a particular emphasis on the difference between continuous and interrupted cutting. The experimental results showed that, despite the fact that severe tool wear occurs in interrupted cutting under the conventional coolant supply condition, compared with continuous cutting, the HPC is significantly effective for suppressing tool wear even under the interrupted cutting condition. Additionally, the mechanism for suppressing tool wear caused by HPC supply was discussed and clarified. Then, a new coolant supply strategy, which is referred to as non-fixed pressure (NFP) coolant in this study, was proposed for high performance interrupted cutting based on the clarified mechanism. The NFP coolant operation provides a variable coolant pressure supply according to the stage (cutting volume) of interrupted cutting. The experiments performed with the NFP coolant supply condition demonstrated excellent wear suppression in the interrupted cutting of Inconel 718.

Tool Wear of Cubic Boron Nitride in Intermittent Cutting of Hardened Steel ASTM D2 with High-Pressure Coolant Supply

To clarify the effect of using high-pressure coolant supply in combination with the intermittent cutting of hardened steel ASTM D2, intermittent cutting of hardened steel was performed with various sintered cubic boron nitride compact (cBN) tools. The result revealed that it was effective to use a high-pressure coolant supply method in combination for intermittent cutting of hardened steel. An effective tool material had a bonding phase of WC-Co-Al and a high content of cBN particles. Furthermore, the more suitable cutting edge shape was "a negative-land width of 0.13mm, a negative-land angle of 45°, and R honing of 0.04 mm".

Machinability investigation and sustainability analysis of high-pressure coolant assisted turning of the nickel-based superalloy Inconel 718

In recent years, issues related to eco-friendly machining have received more and more attention, leading to the development of new cooling/lubrication techniques. Herein, the paper investigates the effect of high-pressure coolant (HPC) supply on machining performance of Inconel 718 and compare with conventional flood cooling. Significant improvement in tool life, tool wear, tool-chip contact length, material removal volume, and cutting forces have been observed from the outcomes of HPC cooling condition. Moreover, in order to study the environmental impact of machining Inconel 718, a carbon emissions model was established and analyzed for high-pressure and flood cooling conditions, taking into account the carbon emissions from energy, material, cutting tool, and cooling/lubrication fluid. HPC assisted machining was revealed to be better as it makes possible a reduction in overall carbon emissions at higher cutting speeds. In addition, economic analysis for both cutting environments was also carried out. Significant improvement in reduction of the overall machining cost was observed under HPC conditions, especially at higher cutting speeds. In a nutshell, the findings revealed better performance of HPC assisted machining, with regard to machinability, environmental, and economic issues.

Tool wear characteristics in rough turning of Inconel 718 with coated carbide tool under conventional and high-pressure coolant supplies

The machining of nickel-based superalloys is often challenging due to their excellent physical properties. High-temperature gradients are generated at the cutting zone, which accelerates the tool wear and impairs its performance. However, introducing high-pressure coolant (HPC) lubrication has been shown to improve both the tool life and surface integrity. In this investigation, attention has been mainly focused on the tool wear characteristics in the rough turning of Inconel 718. The longitudinal turning experiments have been conducted under conventional and HPC lubrication with two cutting speeds. Coated carbide inserts have been analyzed using several techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and 3D scanning. The experimental procedure has embraced the tool life, the tool wear, the generated forces, and the wear mechanisms. The examination of the worn tool surfaces demonstrates that although the depth of cut notching is more pronounced, it is possible to reduce the flank wear by using HPC lubrication. The results also highlight a marginal reduction in cutting and axial forces, a good chip fragmentation, and a significant improvement of the tool life. Furthermore, the investigations show that the wear mechanisms are strongly influenced using HPC under the various investigated cases.

Experimental investigations on surface integrity and chip morphology in hard tuning of AISI D3 steel under sustainable nanofluid-based minimum quantity lubrication

Efficient cooling and lubrication techniques are required to obtain sustainable machining of difficult-to-cut materials, which are the pillars of aerospace, automotive, medical and nuclear industries. Excessive cutting fluid is required and consumed in machining difficult-to-machine materials with high-pressure coolant supplies. Nanofluid-assisted minimum quantity lubrication (NFMQL) is adorned with improved machining performance and environmental sustainability. The present work addresses the surface integrity and chip morphology in finish hard turning of AISI D3 steel under NFMQL condition. The surface integrity aspects include microhardness, residual stress, white layer formation, machined surface morphology, and surface roughness. This experimental investigation aims to explore the feasibility of low-cost multilayer (TiCN/Al2O3/TiN) coated carbide tool in hard machining applications and to assess the propitious role of minimum quantity lubrication using graphene nanoparticles with enriched radiator coolant-based nano-cutting fluid for machinability improvement in hardened steel. Combined approach of central composite design—analysis of variance, desirability function analysis, and response surface methodology, has been subsequently employed for experimental investigation, predictive modelling, and optimization of surface roughness. With a motivational philosophy of “Go Green-Think Green-Act Green”, the work also deals with economic analysis and sustainability assessment under environmental-friendly NFMQL condition. It is expected that the found optimized parameters can contribute to machining end-outcomes such as an improved surface finish and reduced machining cost. The results showed that machining with NFMQL provided an effective cooling–lubrication strategy, safer and cleaner production, environmental friendliness and assisted in improving sustainability. In conclusion, the proposed NFMQL turning strategy is a robust method validated by statistical analysis for large industrial applications, especially in mould and die making sectors.

Chip Breakability in Turning of 7075 Aluminium Alloy with a High-Pressure Coolant Supply

Because of its extremely high strength to weight ratio, 7075 aluminum alloy is used for highly stressed structural parts including aircraft fittings, gears and shafts and various other commercial aircraft, aerospace and transportation equipment. In the case of cutting aluminum alloys, the chip breakability is the most important feature to ensure reliable operation in automated machining. In this study, in turning of 7075 aluminum alloy with a high-pressure coolant supply, the chip configurations, and the mass and thickness of chips were experimentally investigated. The following results were obtained:(1) In the case of a cutting speed of 5.0 m/s, a feed rate from 0.05 mm/rev to 0.50 mm/rev and a depth of cut from 0.1 mm to 3.0 mm, chips were not broken at a feed rate of 0.15 mm/rev or less with the conventional coolant supply. With a high-pressure coolant supply, the combination area of feed rate and depth of cut in which chips were broken was wider than that with the conventional coolant supply. With the high-pressure coolant supply at a coolant pressure of 7 MPa, there was a combination area of feed rate and depth of cut in which chips were not broken. However, chips were broken in all areas at a coolant pressure of 20 MPa.(2) In the case of both the high-pressure coolant supply, which has a coolant pressure of 7, 14 or 20 MPa, and the conventional coolant supply, the thickness of chip increased with the increase of the depth of cut. And, the thickness of chip did not change depending on the cutting method, namely the high-pressure coolant supply cutting method and the conventional coolant supply cutting method.

The role of high-pressure coolant in the wear characteristics of WC-Co tools during the cutting of Ti–6Al–4V

Aeronautic applications have been making use of titanium alloys for decades. Ti–6Al–4V is one of the most commonly applied alloys, and although its mechanical properties warrant its acceptance for many applications, the machinability of this alloy remains a challenge. So far, the most successful technique in facilitating this alloy's machining has been the application of High-Pressure Coolant Supply (HPC) on account of its influence on the tribological aspects of the cutting operation. On that premise, this work employs experimental and computational resources to advance the current understanding of the wear mechanism in terms of the tool-chip contact conditions and establish a correlation between coolant pressure, cutting speed, tool life, cutting forces, and chip formation when machining Ti–6Al–4V with HPC supply. Results showed that HPC plays a role in the reduction of tool-chip temperature profiles and contact stresses, positively impacting tool flank wear, oxidation levels and chip formation, also improving chip breakability.

High speed machining of near-beta titanium Ti-5553 alloy under various cooling and lubrication conditions

Extreme tool wear resulting in short tool life is one of the main issues in the cutting process of near-beta Ti alloys. This study provides extensive experimental results and new findings that help to understanding progressive tool wear and the corresponding measures in high speed machining of Ti-5553 alloy under various coolant and lubrication (dry, flood, high-pressure coolant, MQL, and Cryogenic cooling) conditions at finish and semi-finish cutting. Cutting temperature, progressions of tool wear, and tool life are presented. Besides, cutting forces, frictional conditions, and chip morphology are studied. This current work provides evidence that supports the argument that the feasibility of high speed machining of near-beta titanium alloys that depends on cutting conditions, namely coolant and lubrication used during machining. It was found that tool wear is developed by an abrasive and adhesive mechanism, and built-up-edge formation is a common problem in the machining of this alloy. A high pressure coolant supply with its cooling and lubrication ability was found to be very helpful for decreasing the coefficient of friction and temperature during the process, consequently lowering progression of wear and cutting force components when compared to other cooling and lubrication conditions tested in this study. The greatest tool life is achieved by high-pressure coolant supply, and cryogenic cooling achieves the second greatest tool life. Minimum quantity lubrication is found to be inefficient for improving the machining performance of this alloy. Finally, it is found that the selected depth of cut has vital effect on the penetration capability of cooling and lubrication in between tool and chip, and consequently, it plays a significant role in the contribution of cooling and lubrication to the machining performance of this alloy.

Characterization and prediction of chip formation dynamics in machining austenitic stainless steel through supply of a high-pressure coolant

Use of a high-pressure coolant supply (HPC) can lead to a considerable improvement in machining performance and process stability during the cutting of difficult materials such as stainless steels. Due to the high pressure of the coolant jet, a hydraulic wedge was formed at the tool–chip interface and thus reduced tool–chip contact length and friction behavior. Moreover, the cutting stability can be enhanced as a result of efficient chip breakability. The goal of this work is to evaluate how chip morphology is influenced by three thin jets of pressurized coolant directed into the tool–chip interface during machining of AISI 304 austenitic stainless steel and compare the resulting performance of the tool with dry and conventional coolant conditions. Furthermore, this research evaluates the influence of tool wear on the chip forming mechanism during the turning process. An analysis of the chip generated under machining emphasizes the hypothesis that variations in the cutting tool wear directly affect the chip shape and type of chip segmentation. Finally, a theoretical model was developed to predict the chip upcurl radius under HPC machining. This model is based on shear plane and structural mechanical theories which evaluate plastic strain and the bending moments along the length of the curled chip. The chip upcurl radius values from the developed theoretical model were found to be in good agreement with those measured in the machining tests.

Sustainability assessment of dry turning Ti-6Al-4V employing uncoated cemented carbide tools as clean manufacturing process

Cutting fluid in machining process brings negative impacts on environment and operator health. Excessive cutting fluid is required and consumed in machining difficult-to-machine materials with high-pressure coolant supplies (HPCS). Dry cutting as clean manufacturing technology can eliminate the cutting fluid hazards. This work investigated the tool usage assessment, machining process variables, and surface topography under dry and HPCS conditions employing uncoated WC/6%Co fine tools. The Product Sustainability Index (PSI) approach was applied to establish the sustainability assessment involving machining process and surface quality. Tool life of dry cutting (v = 75 m/min, f = 0.1 mm/rev) achieved 75.8% of corresponding HPCS. Normal wear stage proportion in dry cutting was relatively larger. Higher cutting parameters exacerbated tool wear rate resulting in rapid edge damage, especially in dry cutting. The cutting forces, friction coefficient and specific cutting energy were associated with Ti-6Al-4V softened and specific tribological behaviors accompanied with different cutting parameters. The decisive factor of Sa depended on feed rates. Feed marks in dry cutting were eliminated due to heat softening and lateral pressure, resulting in Sa decreasing. The noticeable difference existed in Sdr for dry cutting while HPCS had a slight fluctuation for the whole cutting parameters. Under dry cutting (v = 75 m/min, f = 0.1 mm/rev), the highest sustainability index was obtained 70.0. The results indicated that dry cutting provided environmental friendliness, cleaner productions and helped to enhance sustainability.

Evaluation of Performance of Various Coolant Grades When Turning Ti-6Al-4V Alloy With Uncoated Carbide Tools Under High-Pressure Coolant Supplies

This work presents the evaluation of three commercially available coolant grades (dicyclohexylamine-based coolant, a triethanolamine-based coolant, and an ester-based coolant) when machining Ti-6Al-4V alloy with high-pressure coolant delivery. The evaluations were based on tool life, tool failure modes, surface integrity, and chip formation. The dicyclohexylamine-based coolant was the more effective coolant when machining at the highest pressure of 20.3 MPa due to its stability at elevated temperature, whereas the triethanolamine-based coolant performed effectively at a pressure of 11 MPa due to its low surface tension properties. Deterioration of the ester-based coolant was found in almost all coolant pressures due to its low resistance to oxidation. Surfaces generated when machining with all coolants grades were generally acceptable with negligible physical damage.

Influence of the coolant nozzle orientation and size on the tool temperature under high-pressure coolant supply using an analogy test bench

In many examinations, high-pressure coolant supply showed its’ great potential to improve the productivity when machining difficult to cut materials. However, most examinations regarding the supply of metalworking fluid at elevated pressure were performed in turning. Accordingly, a profound knowledge of the fundamental mechanisms of the focused high-pressure coolant supply in milling is vital for an optimal process and tool design and mostly still missing. However, especially the sensor-based examination of the cooling effect on the tool temperature in milling under coolant supply is highly challenging, because the rotation of the tool prevents the direct application of temperature sensors in the tool. Therefore, an analogy test bench for lathes was developed to generate an interrupted cut and chips with a non-constant undeformed chip thickness h. With this test bench, different coolant supply strategies with different coolant nozzle orientation, coolant supply pressure and volumetric flow rate were examined. The results show, that the coolant supply pressure, volumetric flow rate and coolant nozzle orientation have a major influence on the tool temperature. As opposed to this, no major influence was found on the cutting force.

Increasing Energy Efficiency in Turning of Aerospace Materials with High-Pressure Coolant Supply

In the field of machining difficult-to-cut materials like titanium or nickel-based alloys, the application of high-pressure coolant supply may result in a significant increase in productivity and process stability. Due to enhanced cooling and lubrication of the cutting zone and thus reduced thermal tool load, tool wear can be decreased which allows higher applicable cutting speeds. Furthermore, the process stability can be increased as a result of effective chip breaking and chip evacuation. Since energy efficiency is very crucial, pressure and flow rate have to be adjusted carefully and in accordance with the cutting parameters to guarantee best results with less energy. For this purpose, experimental investigations were carried out with variation of the coolant flow rate for a given coolant pressure in order to find the minimum required value for a certain machining task with the overall aim to prevent waste of the media used. To maximise the positive effect of high-pressure coolant supply strategy on productivity and process stability, specially designed coolant jet guidance geometry on the rake face was also investigated and compared to conventional tools in turning aerospace materials TiAl6V4 and Inconel 718.

Flank wear characteristics of WC-Co tools when turning Alloy 718 with high-pressure coolant supply

In the present study, the tool wear mechanisms of uncoated cemented tungsten carbide (WC-Co) tools during machining Alloy 718 with high-pressure coolant supply are investigated. Worn flank faces are analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). With increasing spiral cutting length, larger areas on the tool surface are subjected to erosion of Co-binder by the coolant jet impact. Moreover, the amount and morphology of workpiece-precipitates adhered on worn flank surfaces are influenced significantly by the extent of flank wear land (due to increasing spiral cutting length). The reasons for the obtained results are addressed with respect to the underlying mechanisms. Possible implications for the tool wear behavior are discussed.

Experimental and numerical study of chip formation in orthogonal cutting of Ti-5553 alloy: the influence of cryogenic, MQL, and high pressure coolant supply

This study presents investigation of chip formation process of Ti-5553 alloy that is a next generation near beta titanium alloy and has potential to be replaced with commonly used Ti-6Al-4V due to its superior properties such as high corrosion and fatigue resistance. Experimental part of this study includes orthogonal cutting process of Ti-5553 alloy under dry, cryogenic, minimum quantity lubrication (MQL) and high pressure coolant (HPC) conditions. Various cutting speeds were taken into account to observe chip-tool contact length, forces, temperature, chip morphology resulting from various machining conditions. Experimental study demonstrates that HPC and cryogenic help to improve chip formation process of this alloy. By implementing Johnson–Cook model, orthogonal cutting process of this alloy in dry and cryogenic conditions is simulated utilizing Deform 2D commercial software. Predicted force, temperature, and chip morphology show good agreement with experimentally measured data.

Surface integrity and tool life when turning of Ti-6Al-4V with coolant applied by different methods

The main focus of this study is to investigate the behaviour of cemented carbide tools and the surface integrity obtained when turning Ti-6Al-4V alloy. Machining trials were carried out with emulsion cutting fluid applied under conventional and high-pressure supplies and also in an argon-enriched environment. Tool life, cutting force, surface roughness, micrograph and microhardness beneath machined surface were evaluated for better understanding the relationship between the fluid environment and the surface integrity of the machined workpiece. Machining with high-pressure coolant supply generated the best tool life results, while enriched argon showed lower tool life because of the lower conductivity and poor lubrication characteristics of argon gas that lead to heat to be more concentrated at the cutting area, thus weakening the strength of the cutting tool and accelerating tool wear. No plastic deformation was observed on the machined surfaces under the conditions investigated. However, there was evidence of surface hardening after machining with conventional and in an argon-enriched environment due to the poor cooling function of argon. Surface hardening was minimal after machining with high-pressure coolant supplies.

Analysis of High-pressure Coolant Supply Conditions on Cooling Efficiency of Drilling Process

Cutting tools tend to wear gradually with progressing of machining process due to extremely high surface loads and temperature from the relative motions between tool and workpiece. Especially, the high cutting temperature is a dominant factor in the relation to tool life. High-pressure coolant has been reported as an effective method to prevent the severe wear from cutting temperature. This research investigates efficient supplying conditions of high-pressure coolant with the CFD results from a internal-flush drilling process. The flow rate of coolant is increased drastically up to three times under 70 bar compared to conventional way.

Hard turning of bearing steel AISI 52100 with carbide tool and high pressure coolant supply

The machining of hard-to-machine bearing steel AISI 52100 (100Cr6), hardened to 62 HRc, is almost impossible using standard machining conditions and carbide cutting tools. The purpose of this research is machinability analysis and conclusions about the conditions that allow the machining of mentioned steel with carbide tools. In this paper, the turning process is carried out using coated carbide inserts and high pressure jet assisted machining, as a special technique of cooling and lubrication. In this technique, coolant circulation system with filters, environmentally acceptable, is used. A jet of cooling and lubrication fluid under extremely high pressure (50 MPa) is directed into the zone between the cutting tool edge and the workpiece. Experimental measurements were performed for different cutting parameters. Cutting forces, tool wear, surface roughness, chip shapes, and material removal rates were analyzed. The presented results show an increase in productivity, low intensity tool wear, and surface roughness in acceptable limits.

Effect of High-Pressure Coolant Supply on Chip-Breaking and Tool Wear in Machining of Stainless Steel

The high-pressure coolant supply cutting has attracted attention from a viewpoint of chip evacuation and tool life. In this study, the influence of high-pressure coolant supply on chip shape, cutting force and tool wear were investigated. The tests were carried out during external turning of stainless steel with cemented carbide cutting inserts. The results suggest that the length and radius of the chips got shorter with high-pressure coolant supply, especially supply pressure more than 5MPa. The cutting force was increase slightly with high-pressure coolant supply. However the thrust force was decrease. The uniform flank wear and crater wear were reduced and tool life was improved by high-pressure coolant supply.