Flood Coolant Research Articles

Machinability analysis of nickel-based superalloy Nimonic 90: a comparison between wet and LCO2 as a cryogenic coolant

The usage of cryogenic fluid is increasing in the machining industries especially to cut the materials having a lower machinability like Nimonic 90, a nickel-based alloy. However, the comparison of flood coolant and LCO2 as a cryogenic fluid based on machining performance has not been found for machining Nimonic 90. In this regard, this study compares LCO2 and conventional mineral oil-based flood coolant on the basis of machining performance while turning Nimonic 90. The effect of turning process parameters (cutting speed (vc), feed (f), and depth of cut (ap)) and cutting fluids has been identified by analyzing machinability indicators like cutting force, flank tool wear, power consumption, surface roughness in terms of Ra, and chip morphology. Increment of 34%, 25%, and 24% in cutting forces has been observed for cryogenic turning using LCO2 in comparison with wet machining when the values of ap are 0.75, 0.50, and 0.25 mm, respectively. A decrement of 63% tool wear has been seen in LCO2 cryogenic fluid in contrast to wet machining at higher values of vc, f, and ap. The superior surface finish has been found in wet machining, while lesser power consumption was recorded for LCO2 as a cutting fluid. Cryogenic machining provided better chip breakability in comparison with wet machining.

Experimental investigation into tool wear, cutting forces, and resulting surface finish during dry and flood coolant slot milling of Inconel 718

Inconel 718 superalloy is a widely used material in aerospace due to its high strength, corrosion resistance, and high resistance to thermal fatigue. Excellent mechanical and thermal properties also make Inconel 718 one of the most difficult-to-machine alloys. This study aims to take a different approach of analyzing tool wear during machining of Inconel 718 by measuring worn-out area on each flute from three different faces of flute. This paper also includes analysis of cumulative tool wear, cutting forces, surface roughness, topography, burr formation, and chip morphology at various machining parameters and cooling conditions. The cutting speed was kept constant at 60 m/min due to the goal of machining at highest possible speed and the limitation in maximum spindle speed of the machine tool. Experiments were carried out in dry and flood coolant machining using uncoated carbide tools by varying depth of cut and feed rate for four different settings each. It was found that the amount of tool wear varied for different flutes when measured from top, rake, and back faces of each flute, even for the same tool. The back and rake faces exhibit more chipping wear when machining is carried out at higher depth of cut, irrespective of the cooling conditions. At the same machining conditions for the range of parameters selected in this study, flood coolant machining resulted in slightly higher tool wear at the back and rake faces of cutting flutes and generated higher cutting speed, which may be interrelated. The gradual increase in tool wear over time resulted in an increase in surface roughness from entry to exit of a 76.2 mm machined slot. Flood coolant machining resulted in slightly smoother surface finish at the lower settings of depth of cut and feed rate, while the burr formation was marginally higher in flood coolant machining during machining at higher feed rate and depth of cut. The amount of serration was found to increase specifically with the increase of feed rate and was found to be higher for dry machining compared to flood coolant machining at the same parameter settings. Finally, the new approach of tool wear analysis from different faces of individual cutting flute could provide important guidelines for predicting tool life or potential catastrophic tool failure during machining of Inconel 718.

Energy Consumption and Lifecycle Assessment Comparison of Cutting Fluids for Drilling Titanium Alloy

This study analyzes four cutting conditions (dry, flood, Liquid CO2 (LCO2), and Liquid N2 (LN2)) based on energy consumption and ecological impacts for drilling VT-20, a Titanium alloy. The lower cutting and total energy have been consumed for LCO2 as compared to others. The Life Cycle Assessment (LCA) analysis has been performed using ReCiPe 2016 midpoint (H) to identify the impact of cutting conditions on ecosystem, human health, and natural resources. Cryogenic environment with LN2 has been found as the most ecological cutting condition next to dry machining, while flood coolant has 94-99% of total impact considering all cutting conditions.

Implementation and optimization of minimum quantity lubrication for machining LM4 aluminium alloy

The cooling method employed in machining processes plays a vital role in the surface quality and the efficiency of the process. Dry machining is being performed for flat milling operation on LM-4 alloy. This has resulted in poor surface roughness and increased tool wear rate. The other type of cooling installed in the industry is the flood coolant method which uses enormous coolant flow rate. Hence the scope of our project is to enhance the surface finish with reduced coolant flow rate and tool wear rate by introducing the Minimum Quantity Lubrication system which sprays a mixture of compressed air and lubricant in a form of mist at the point of operation i.e. tool workpiece interface. The optimized air pressure, siphon height and coolant concentration ratio are determined based on the results obtained from the surface roughness tests and the coolant flow rate measurements. Both single objective and multi objective optimization are done with the help of Taguchi analysis and Grey relational analysis respectively. Finally, this optimized MQL system is implemented in the Industry and its results are found to be in tune with our project outcome.

Environmentally sustainable cooling strategies in milling of SA516: Effects on surface integrity of dry, flood and MQL machining

Abstract The recent move towards ‘Environmentally Sustainable Manufacturing’ (ESM) is leading heavy industries (e.g. oil & gas, nuclear) to explore low-impact manufacturing strategies. In machining, however, most processes are still performed using traditional cooling method using flood or high pressure lubricant emulsions. These emulsions are expensive in their maintenance and disposal, and present a significant environmental concern. This novel study combines evaluations of the performance of low-impact cooling strategies, such as dry milling or minimum quantity lubrication (MQL), in the manufacture of an industrially important pressure vessel carbon steel (SA516) using coated carbide inserts. Tool wear, surface roughness, residual stress and energy consumption were measured during metal cutting trials for each strategy and then compared. Likely tool wear performance when using candidate lubricants was screened prior to machining trials using standard tribological high frequency reciprocating tests. Significant improvements in surface integrity and tool wear were observed when machining with dry and MQL when compared with traditional flood coolant. Measured energy footprints for dry and MQL were also lower when compared to flood coolant machining providing cost savings and environmental advantages in manufacturing using ESM approaches.

Characterization and Performance of Minimum Quantity Lubricants in Through-Tool Drilling

This study characterized airborne microdroplet diameters and size distribution from two commercially available lubricants A and B for internal minimum quantity lubrication (MQL). The effects of air pressure, oil channel size, physical properties of lubricants on the resultant microdroplets and through-tool MQL drilling performance were studied. Airborne microdroplet diameters were highly sensitive to the coolant channel sizes and air pressure. Cluster method was used to divide microdroplets into smaller clusters for comparison. Experimental data show that the average airborne microdroplet of lubricant B was larger than that of lubricant A at different air pressures and channel sizes. The contact angle of lubricant A was at least 10° less than that of lubricant B when depositing on glass or aluminium. High-speed imaging showed the tendency of more viscous lubricant B sticking to the drill tip, and higher pressure and longer time was required to atomize this viscous oil. Built-up-edges were less significant when drilling A380 aluminium with lubricant A. Due to high machinability of A380 aluminium, variation of hole diameter and hole cylindricity were minimal when drilling with different lubricants. Insignificant improvement in hole quality was observed when drilling with excessive amount of MQL lubricants or high concentration of lubricant C in flood coolant.

Application of Minimum Quantity Lubrication for Various Machining Processes – A Mini Review

Minimum Quantity Lubrication (MQL) is a great alternative lubricating and cooling environment method that has been widely used to replace the conventional flood coolant which brings drawbacks involving environmental awareness, human’s safety and health and manufacturing cost. Taking into account the recent trends, this review paper describes a summary of the research journals reviewed previously MQL in various machining operations involving milling, turning, drilling and grinding of various types of materials. Most recent papers have described the use of vegetable oils which helps in maintaining the environmentally friendly machining. Also, the aided of nanofluid particles and hybrid environment in MQL application conversed the outstanding efficiency in machining performances as compared to that conventional flood lubrication technology. Briefly, this paper have shown the proficiency of eco-friendly MQL approach in improving the performance of machinability such as reducing the surface roughness of workpiece, producing a higher rate of tool life and also reducing the cutting temperature that leads to a sustainable machining environment in the future work.

A comparative study on coated carbide inserts performance in cryogenic end milling of AISI D2 tool steel

Cryogenic metal removal with the help of liquid nitrogen will be a clean substitute for our conventional flood cooling due to environmental regulations in the machining industries. The present work experiments the efficiency of TiN as well as TiAlN layered insert of carbide in the process of milling which takes place at the end in AISI D2 steel. The performance caused by cryogenic machining for the finishing on the surface and tear and wear of the tool are studied, the results are estimated with dry and existing flood coolant metal removing process at different cutting speeds. When estimated with TiN layered inserts, inserts of TiAlN shower maximized life of the tool and maximized finishing in the surface during metal removing process at several speeds behind their spindle, more than that they are environmentally clean metal removing process. We are going to discuss the significance of the cryogenic metal removal process which provides its importance for increased efficiency of machined components through its better penetration of lubrication in the tool and workpiece interface.

An integrated numerical study for using minimum quantity lubrication (MQL) when machining austempered ductile iron (ADI)

Machining difficult-to-cut materials is still an ongoing area of research because of the promising advantages of these materials in different industrial applications. Austempered Ductile Iron (ADI) is among the difficult-to-cut materials as it is usually associated with short tool life and poor surface integrity and quality. Flood coolant is an effective approach to eliminate the high generated heat when machining ADI. However, the use of conventional flood coolant is not a sustainable approach. Minimum quantity lubrication (MQL) is one of the environmentally friendly cooling approaches, which has been demonstrated to be an effective near dry machining technique. There is a gap in the open literature in the area of numerical modelling of the thermal and heat transfer behavior when machining ADI. Thus, this research focuses on simulating the cutting heat distribution on the cutting tool during machining of ADI by developing an integrated numerical model (finite element & computational fluid dynamics). Two cooling techniques were used in this work namely; dry and MQL. In terms of dry cutting, the simulated temperature values were in good agreement with the experimental results with an error of 5.74%. Regarding the MQL, there was a 10.74% margin of error between the results from the experimental and the integrated numerical model.

Study of surface integrity of milled gamma titanium aluminide

This paper presents a comprehensive investigation of the effects of cutting parameters on the surface integrity of milled γ-TiAl alloys. Surface topography, surface roughness, surface defects, plastic deformation, micro-hardness, chip morphology, and tool wear of the milled γ-TiAl alloys were analyzed. The results indicate that the feed rate had the greatest influence on the surface topography and surface roughness. The value of surface roughness increased with the increase in cutting depth and feed rate. However, with the increase in cutting speed, it initially increased and then decreased. The minimum surface roughness was found to be 0.066 μm. The thickness of the plastic deformation layer and the micro-hardness value increased with the increase in cutting depth and feed rate. Also, they initially increased and then decreased with the increase in cutting speed. The minimum thickness of the plastic deformation layer was 15 μm and the depth of the hardened layer on the processed surface varied between 55 and 70 μm. The chip morphology was closely related to the quality of the processed surface. When the cutting depth and feed rate decreased, the chip morphology was transformed from segmented to nearly smooth. When the cutting depth and feed rate reached a critical point, plastic processing of γ-TiAl was achieved. Compared to brittle deformation, a more favorable processed surface was obtained. Finally, the comparison tests of tool wear were carried out with dry and flood coolant cutting. When the cutting speed reached 120 m/min in dry cutting, the tool life was very poor, and the cutting distance was only 1 m. However, the tool life was generally good when cutting with low cutting speed under the following conditions: vc = 60 m/min, ap = 0.1 mm, and fz = 0.01 mm/tooth. Under these conditions, the cutting distance was 60 m in dry cutting with the tool wear of 0.2 mm and 120 m in flood coolant cutting with the tool wear of 0.1 mm. The tool life in flood coolant operation was better than that of dry operation. The tool life decreased to 30 m when cutting with high cutting speed or feed rate (ap = 0.25 mm or fz = 0.025 mm/tooth).

The wear mechanisms of diamond grits in grinding of alumina and yttria-stabilized zirconia under different cooling-lubrication schemes

Abrasion is the primary wear mechanism of diamond grits during grinding of advanced ceramics. This work not only highlights some unreported modes of wear of diamond grits but also illustrates and describes their mechanisms while grinding two dissimilar advanced ceramics, viz. alumina and yttria-stabilized zirconia (YSZ). Long-cycle plunge grinding of the ceramics was conducted with single-layer electroplated diamond wheels at 30 m/s and 50 m/s grinding speeds under three different cooling-lubrication schemes – flood cooling (FC), MQL-soluble oil (MQL-SO) and MQL-neat oil (MQL-NO). Radial wheel wear was measured employing indirect profilometry. Diamond grits on the electroplated wheels were observed under SEM before and after grinding to identify and characterize various modes of wear. Severe wheel loading was observed while grinding alumina and YSZ under FC and MQL-SO. Indentation fatigue fracture was found to be the dominant mode of diamond grit wear during alumina grinding under wheel loading conditions. The wear of diamond grits during YSZ grinding was dominated by thermal fatigue fracture at a higher grinding speed of 50 m/s. Thermal degradation of diamond grits was examined with Raman spectroscopy which revealed graphitization of some of the active diamond grits after YSZ grinding under FC and MQL-NO at 50 m/s.

Toward sustainable micro-drilling of Inconel 718 superalloy using MQL-Nanofluid

The application of micro-mechanical cutting operations, such as micro-drilling, is crucial for producing microsystem components. In the production of jet engine parts, Inconel 718 superalloy has been used to produce these components due to its high performance at high temperatures. Due to the low thermal conductivity and the high work hardening tendencies of Inconel 718, a high amount of the cutting temperature dissipates toward the cutting tool instead of the chip. When using micro-scale drilling (micro-drilling), heat dissipation becomes more challenging. This affects the tool life and the machined surface quality; therefore, when machining these alloys, a cutting fluid is required to decrease the high amounts of generated heat. Flood coolant is commonly used to reduce the cutting temperature; however, government regulations have been published for alternative cooling processes to decrease the influences of flood coolant on the environment and the operator’s health. Minimum quantity lubrication (MQL) has been used as an alternative to conventional cutting fluids because it minimizes the consumption of cooling lubricants and reduces the environmental and health impacts; however, pure MQL cooling has an ineffective cooling ability. In order to enhance thermal conductivity, viscosity, and wettability of the MQL base fluid, an MQL-nanofluid was used. This study investigated the performance of a micro-drilling process using an MQL-nanofluid with regard to thrust forces, tool wear, and burr formation, and compared it to flood cooling and a pure MQL. Micro-drilling experiments involving Inconel 718 were conducted using the same cutting parameters, drilling tool, and machining environment for both the MQL and the flood coolant. The results revealed that the MQL-nanofluid approach was promising in terms of machining outputs as well as sustainability.

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

The objective of this research is to investigate the morphology and microstructure of the chips formed during milling of Ti-6Al-4V alloy using conventional flood coolant and sustainable dry and MQL machining conditions. It was found that the chips formed in dry machining suffered a higher degree of serration indicating higher chip temperature and ineffective cooling of the chips. The bi-modal structure of Ti-6Al-4V remained the same in the bulk part of the chips. However, phase transformations were seen for all three machining conditions at the shearing plane of the chips. The chips formed in dry machining had comparatively higher percentage of β-phase due to phase transformation. For the chips obtained in flood coolant machining, the transformed β-phase possibly returned to martensitic α-phase due to rapid cooling. The MQL machined chips had the least transformation of β-phase, indicating minimal changes in mechanical properties of the machined parts in sustainable MQL machining.

Regression modeling and comparative analysis on CNC wet-turning of AISI-1055 & AISI-4340 steels

This study focuses on the investigations of regression models and the comparative analysis in CNC turning of AISI-1055 & AISI-4340 steels under wet-condition in terms of average surface roughness (Ra) and material removal rate (MRR). In this study, optimal cutting-parameters were also investigated to minimize the “Ra” and maximize the “MRR” in CNC wet-turning of AISI-1055 & AISI-4340 steels using Taguchi design method. All the experiments were conducted with cutting tool-insert of coated cemented carbide under wet-cutting condition using conventional cutting fluid (flood coolant) and using L9 Taguchi orthogonal array (OA) design. A statistical analysis method, analysis of variance (ANOVA) was employed to investigate the influence of cutting-parameters on Ra and MRR. All the experimental data obtained for Ra and MRR were utilized to develop second-order regression-models. The developed regression-models for both Ra as well as MRR could be utilized to predict the responses in CNC wet-turning of AISI-1055 & AISI-4340 steels with a very small error. At last, a comparison between AISI-1055 and AISI-4340 steels on the basis of Ra and MRR obtained in CNC wet-turning were carried out. Comparative analysis between CNC wet-turning of both the materials show that the machinability of AISI-4340 steel is better than the machinability of AISI-1055 steel on the basis of Ra and MRR obtained

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

Investigating the microstructure and morphology of chips in dry, flood coolant and MQL machining of Ti-6Al-4V alloy

Investigations on effect of nanofluid based minimum quantity lubrication technique for surface milling of Al7075-T6 aerospace alloy

Machining is one of the largest and significant manufacturing processes. Due to strict environment regulations and water scarcity, reduction in the usage of coolants/cutting fluids has been the need of the hour. The present work focuses upon Analysis of Variance (ANOVA) based investigations using full factorial design on the effect of Minimum Quantity Lubrication (MQL) coolant supply instead of conventional flood coolant method, for surface milling of aerospace Al7075-T6 Aluminum slabs using uncoated carbide tool. Parameters chosen were spindle speed, feed rate and depth of cut with spindle speed in terms of rpm (3000, 4000, 5000, 6000, 7000), feed rate in mm/min (95, 105, 110, 115, 125) and depth of cut in mm (0.5, 1.0, 1.3, 1.6, 2.0). Out of 3 methods of coolant supply, MQL technique yielded superior results compared to dry milling and nanofluid MQL milling, in terms of surface finish (Ra) and minimum temperature values (T) that were observed for nanofluid MQL coolant supply technique. Addition of nanoparticles to the coolant has provided good effect in reducing the temperature at the work tool interface, without affecting the milling performance characteristics.

Assessment of tool wear and microstructural alteration of the cutting tools in conventional and sustainable slot milling of Ti-6Al-4V alloy

This research presents both qualitative and quantitative analyses of tool wear during slot milling of Ti-6Al-4V alloy under conventional flood coolant and sustainable dry and minimum quantity lubrication (MQL) machining conditions. The microstructures of the cutting tools near the cutting edges have been analyzed for understanding the effectiveness of tool coating and the influence of tool wear and machining conditions on the tool microstructure. The abrasion wear was measured using maximum flank wear (VBmax) and the length over which the flank wear occurred. The chipping wear was measured using the surface area of the material chipped off from the cutting edge or tool nose. In addition, the correlations between the abrasion and chipping wear with plastic failure were investigated. It was found that the average magnitudes of VBmax and length were lower in MQL machining. The calculations of the surface area of chipped materials indicate comparatively lower chipping wear in MQL machining. Both the abrasion and chipping wear occurred along with plastic failure, indicating correlations among those wear mechanisms. It turned out that the TiAlN-coating was more effective in the reduction of tool wear under dry machining conditions. Delamination wear was observed under flood and MQL conditions, illustrating the effectiveness of coated tools under dry machining conditions. The microstructural analysis of the worn-out uncoated tools indicates plastic deformation and grain refinement underneath the tool wear, whereas this effect is less severe in coated tools. Conclusively, sustainable dry machining with TiAlN-coated tools and MQL machining resulted lesser tool wear, indicating the effectiveness of sustainable machining processes for Ti-6Al-4V alloy.

Evaluation of surface and sub-surface integrities of a mold steel under different grinding conditions

In a context where there is a continuous search for more environmentally friendly machining processes (for example, the implementation of the minimum quantity of lubrication—MQL—cooling–lubrication technique) and the constant concern with the high heat generation during the grinding process, there is still a lack of information about grinding of steel for molds and dies. Thus, the present work sought to evaluate the performance of tangential surface grinding of a steel for plastic injection molds, testing by two types of conventional abrasives (green silicon carbide and white aluminum oxide) under three different equivalent chip thicknesses. The performance of the MQL cooling–lubrication technique compared to the conventional one (flood coolant) was also evaluated. The output parameters to assess the surface integrity were the surface roughness (Ra parameter), residual stresses and SEM images of the ground surfaces, as well as microhardness below the machined surface. The results shown that both conventional abrasives types have potential to be used in grinding of this steel, once low surface finish values (Ra < 0.2 μm) and workpieces free of damages were fabricated. Silicon carbide (SiC) grinding wheel in general outperformed the aluminum oxide (Al2O3) one in terms of surface roughness after machining under severest conditions (Ra < 0.35 μm). Residual stresses were predominantly compressive irrespective of the cooling–lubrication technique and type of abrasive employed. Despite lower surface roughness and compressive residual stresses generated after grinding with the Al2O3 grinding wheel, drop in hardness below the machined surface was observed, unlike when machining with SiC grinding wheel. MQL technique proved to be more effective than conventional coolant technique under the conditions investigated, irrespective of the grinding wheel used, and in some situations, it outperformed the conventional technique.

Hybrid cryogenic MQL for improving tool life in machining of Ti-6Al-4V titanium alloy

It is estimated that there is a need for 37,000 new passenger aircrafts until 2037. About 15% of the modern aircrafts are made of titanium alloys due to their high strength to weight ratio. In typical aerospace manufacturing, there is a buy-to-fly ratio of 6:1 for titanium parts which indicates significant machining requirements. Machining titanium alloys is generally associated with short tool life, poor surface integrity, low productivity and high manufacturing costs. These issues have made Ti-6Al-4V a difficult to machine material.In this study, a new hybrid cryogenic MQL cooling/lubrication technique is proposed for end milling Ti-6Al-4V using coated solid carbide tools. The effect of the proposed system on machinability of Ti-6Al-4V was studied at various cutting speeds and compared with flood, minimum quantity lubrication (MQL) and cryogenic cooling. Tool life, tool wear and surface roughness were thoroughly investigated as key machinability metrices and a new model for tool life based on tool wear is proposed. The analysis indicates a significant shift in CNC milling performance, as the new hybrid cryogenic MQL technique shows an increased tool life of 30 times is achieved together with a 50% improvement in productivity compared to state-of-the-art flood coolant machining.

Impact of supercritical carbon dioxide cooling with Minimum Quantity Lubrication on tool wear and surface integrity in the milling of AISI 304L stainless steel

In this study, the effect of supercritical carbon dioxide cooling with Minimum Quantity Lubrication (scCO2+MQL) on tool wear and surface integrity of AISI 304 L austenitic stainless steel in milling was investigated. A series of machining experiments based on a Design of Experiments (DoE) was carried out at various combinations of cutting parameters to investigate the effect of cutting speed and feed rate on tool wear, near-surface residual stresses, surface roughness and microhardness. The results were compared with the experimental results obtained from milling with flood coolant. A significant improvement in tool life was observed in milling with the scCO2+MQL using multilayer coated tungsten carbide inserts. The tool life in terms of cutting time increased by ∼324%, in comparison to a baseline flood coolant. Further, a decrease in surface roughness value (Ra) by about 30%, from 1.09 µm for flood coolant to 0.78 µm after face milling with scCO2+MQL was seen. Additionally, the Ra value slightly increased after machining, for both cooling methods with the increase of cutting speed of ∼19%. The observed changes in Ra value were discussed in terms of a built-up-edge (BUE) formation. There were no apparent differences in surface microhardness between both cooling methods. However, the surface microhardness increased with feed rate after milling with both scCO2+MQL and flood coolant due to the increased strain hardening. Also, there was no significant difference in residual stresses after milling, neither with scCO2+MQL nor the flood coolant. The surface residual stress values obtained in the transverse and longitudinal directions were consistent with a predictive model with errors of around 3–8%.