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Research Papers

# Evaluation of Cutting Fluid With NanoinclusionsOPEN ACCESS

[+] Author and Article Information
M. Amrita

Department of Mechanical Engineering,
Gitam Institute of Technology,
Gitam University,
e-mail: amritrajvib@gmail.com

R. R. Srikant

Department of Mechanical Engineering,
GITAM Institute of Technology,
GITAM University,
e-mail: r.r.srikant@gmail.com

A. V. Sitaramaraju

Department of Mechanical Engineering,
JNTU-H,
e-mail: avsr_raju2005@yahoo.com

1Corresponding author.

Manuscript received October 4, 2013; final manuscript received February 9, 2014; published online March 10, 2014. Assoc. Editor: Debjyoti Banerjee.

J. Nanotechnol. Eng. Med 4(3), 031007 (Mar 10, 2014) (11 pages) Paper No: NANO-13-1072; doi: 10.1115/1.4026843 History: Received October 04, 2013; Revised February 09, 2014

## Abstract

Environmental and economic concerns on use of cutting fluids have led to use of minimum quantity cooling lubrication (MQCL) system, which uses minute quantity of cutting fluids, demanding a specialized fluid with improved properties. Investigation of any newly developed cutting fluid would be complete if it is evaluated with respect to its machinability, environmental and economic aspects. The present work investigates the viscosity, machinability characteristics, environmental effects, and economic aspects of a newly developed nanocutting fluid with varying concentrations of graphite nanoparticles applied at different flow rates to machining operation. It is found that the machinability improved with respect to conventional cutting fluid and this improvement increased with increase in concentration of nanoinclusions in the range 0.1–0.5 wt. % and also with increase in the flow rate. A regression model is developed for nanocutting fluids to estimate tool wear when used in the range 0.1–0.5 wt. % at flow rates 5 ml/min to 15 ml/min. The biodegradability is found to decrease with inclusion of nanoparticles due to the inorganic nature of selected nanoparticle. But its application as MQCL is ecofriendly as the nanocutting fluid is not disposed to the environment and graphite in it is neither toxic nor hazardous. Based on economic aspect, MQCL application with conventional cutting fluid and few cases of nanocutting fluids are found to be economic compared to flood lubrication. So a compromise has to be obtained between the economic and machinability aspects to choose an optimum cutting fluid.

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## Introduction

Cutting fluids cool and lubricate the interfaces [1] and improve the tribological conditions existing there. Thus, it plays an important role in increasing the efficiency and productivity in industries. But their properties degrade over a period of time during usage. So, maintenance of cutting fluid is a must to keep its properties within advisable range and to increase its life time. Maintenance is performed by daily checking the water make up and weekly checking the biological growth, rust, foam, filterability, surface tension, and dirt load [2]. When it becomes uneconomical to maintain the fluids, it has to be disposed off. This causes environmental concern due to hazardous metal carry-off, hazardous chemical composition, depletion of oxygen and excessive nutrient loading leading to imbalance of ecosystem in water bodies [3]. Many states like United States, Canada, and India have classified cutting fluids as hazardous wastes leading to high disposal costs. Disposal costs range from $0.50/gallon to$12.00/gallon [4].The amount spent on procurement, maintenance, and disposal of cutting fluids vary among industries and states. When a plant has its own cutting fluid disposal facility as in case of an automotive industry, the share of cost due to cutting fluid ranges from 8% to 10% [1]. Based on survey conducted by United States Environmental Protection Agency, TechSolve, Inc., an average machining facility spends an amount of $57,000 for procurement, use, and disposal of the cutting fluid. The amount spent on tools depends on the complexity of the parts to be manufactured. It varies from 12% to 15% for powertrain plants to 5–7% for small plants using simple operations like turning and milling [1]. Moreover, the increasing costs of cutting fluids and tools bring a situation of economic concern. Also, it greatly affects the health of workers. Triethanolamine—a common constituent in all cutting fluids causes asthma and is carcinogenic [3]. Exposure of skin to cutting fluids causes dermatitis. Long time exposure to mist from cutting fluids cause respiratory problems like bronchitis and pneumonitis [1]. The health care negligence at workplace caused social concern. The National Institute for Occupational Safety and Health designed recommendations to protect the safety and health of workers. It recommended that exposure to cutting fluids aerosols be limited to 0.4 mg/m3 of air as a time-weighted average concentration for up to 10 h/day during a 40 h work week [4]. Environmental, social, and economic concerns have lead to the search of sustainable manufacturing methods. This lead to research in the field of environmental friendly techniques which include dry machining and MQCL. In dry machining, no cutting fluid is used. In MQCL technique, very less quantity of cutting fluid is applied at the cutting zone to provide localized cooling and lubrication. This technique uses just sufficient amount of cutting fluid in contrast to that of flood cooling where a large amount of fluid is used and recirculated. So in MQCL technique, there is no need for maintenance and disposal. There are three types of MQCL systems [5]. One is low pressure spray system where cutting fluid is drawn by air and applied as mist. Other uses dosing pump which supplies cutting fluid without use of air. Third is the pressure system where the lubricant (nonwater soluble cooling lubricants) and compressed air are supplied through separate pipes which can be independently adjusted and are mixed and applied at the cutting zone. A lot of work has been done on MQCL to explore its effectiveness over conventional flood cooling in machining process. Yasir et al. [6] studied the effect of minimum quantity lubrication (MQL) on the machinability of Ti-6Al-4 V using physical vapor deposition (PVD) coated cemented carbide tools. They reported that MQL as mist application is most effective at cutting speed of 135 m/min to get better tool life. Wins et al. [7] proposed an environment friendly minimal pulsed jet cutting fluid application scheme for surface milling of AISI4340 steel with a hardness of 45 HRC using commercially available carbide tools. They reported that the new scheme is not only environment friendly but also provided better cutting performance when compared to conventional wet milling. Khan et al. [8] compared performance of vegetable oil based MQL in turning of AISI9310 with dry and wet machining. They reported superiority of vegetable oil based MQL due to reduced cutting zone temperature, favorable chip formation and chip–tool interaction. Li et al. [9] reported improvement in tool life, surface roughness, and burr formation with MQL in near micromilling with respect to dry cutting based on slotting tests. But as less quantity of cutting fluid is used in MQCL, a special fluid having superior qualities than conventional fluids are desired. This led to research in the field of application of nanofluids to machining. Few researchers used oils as the base fluid and few others used water based cutting oils as the base fluids. According to Lee et al. [10] nanofluid MQL is effective for reducing grinding forces and enhancing surface quality. The influence of type, size and volumetric concentration of nanoparticles on the performances of micro-grinding process has also been reported. They used nano-Al2O3 and nanodiamond in paraffin oil. Nam et al. [11] used nanodiamond particles in paraffin and vegetable oils and applied as MQL in micro drilling process. They reported increase in number of holes drilled and reduction in drilling torque and thrust forces compared to pure MQL. Ewald [12] performed MQL-ball milling tests with nanographene enhanced vegetable oil. They reported remarkable performance improvement in reducing central wear, flank wear and edge chipping at cutting edge. Shen [13] used MoS2 nanoparticles in low and high concentrations in different base oils and reported significant reduction in the tangential grinding force, friction and G-ratio. Mao et al. [14] applied water based Al2O3 nanofluid to grinding process using MQL approach. They reported significant reduction in grinding temperature, forces, surface roughness, and improvement in the ground surface morphology compared to wet, dry, and pure water MQL grinding. Setti et al. [15] used water based Al2O3 nanofluids as MQL to improve grinding characteristics of Ti-6Al-4 V alloy. They claimed that grinding forces reduced significantly even at low concentration of the nanoparticles. Surface finish was reported to improve with higher concentration of the nanoparticles. Samuel et al. [16] used graphene platelets (GPL) in semisynthetic metal-working fluids and performed microturning experiments. They reported significant improvement in lubricating and cooling efficiencies. The decrease in cutting temperatures and the cutting forces was also reported with 0–0.5 wt. % fraction range. Works have been reported on use of Al2O3, nanodiamond, GPL, CNTs, MoS2 nanoparticles. Many researchers evaluated the effect of cutting fluids on environment. Gerulová et al. [17] evaluated toxicity and biodegradability of few metal working fluids (MWFs) using chemical oxygen demand (COD) measurement. They reported that these MWFs have potential to ultimate degradation. Gannon et al. [18] determined the biological oxidation capacity of twenty one types of oil-in water MWFs using biological oxygen demand (BOD), COD, and total organic carbon (TOC) analyses. They found that based on the initial COD and/or TOC, the extent of biological oxidation ranged from 1.6% to 35.0% over the five day test period. Effect of nano-MWFs on the environment has to be evaluated. Economic aspect in machining process is also studied by few researchers. Sun et al. [19] developed a cost model based on the process based cost model approach for assessing the return-on-investment of machining process with and without intelligent prediction monitoring system. The effect of microlubrication and flood application on the cost of fluid purchased and disposed is presented in a report by Waste management and Research Center [4]. The cost effectiveness and the economic consequences of the machining with nanocutting fluids have to be evaluated. Graphite, boric acid, and molybdenum disulphide are solid lubricants and have capacity to increase the lubricating properties of base oil. Graphite is available in abundance and has good thermal conductivity, lubricating properties and is also economic. In most of the research works, third method of MQCL system has been applied where water soluble oil, which has better cooling efficiency than other oils, cannot be used and a high pressure compressor and a costly MQL system are required. In the present work, first method of MQCL system has been used. Soluble oil is mixed in ratio 20:1 and graphite nanoparticles are added in different wt. % to formulate nanocutting fluid. The present work investigates the viscosity of nanocutting fluids with varying concentrations of graphite nanoparticles and evaluates their machinability characteristics and economic aspects when applied at different flow rates to machining operation. The results are compared with dry machining, flood lubrication, and MQCL application with conventional cutting fluids. A regression model is developed for nanocutting fluids. The environmental effect of nanocutting fluids is also evaluated. ## Experimentation ###### Materials, Equipments, and Process Parameters. Materials, equipments, and process parameters used in the experiment for evaluating machinability characteristics of nanocutting fluids are shown in Table 1. Set up for experimentation is shown in Fig. 1. An atomizing nozzle is used to mix pressurized air and soluble oil to form fine aerosols to be applied at the cutting zone in the form of mist. Schematic diagram for mist generation is shown in Fig. 2. Materials, equipments, and chemicals used for environmental evaluation are shown in Table 2. ###### Formulation of Nanocutting Fluid. The hydrophobic graphite nanoparticles are surface modified using covalent reactivity via acid-oxidation using 6 M sulphuric acid and nitric acid in the ratio 2:1 for 6 h. This is to induce oxygen functional groups on the graphitic surface which help to form stable dispersion. The functionalized powder obtained is repeatedly washed with de-ionized water and filtered using Millipore membrane type filter to bring the pH of the powder back to neutral. The powder is then dried in vacuum oven at 80 °C for 16 h to get dry surface treated powder. The nanocutting fluid is prepared by adding the surface treated graphite nanopowder in different concentration: 0.1 wt. %, 0.3 wt. %, 0.5 wt. % to water soluble oil (20:1). The mixture is sonicated in high frequency bar sonicator for 5 min and then in bath sonicator for 35 min. The resultant dispersion remained stable for 2 days, after which small amount started settling. As the time for machining is less than this, it is used for investigation. ###### Viscosity Measurement. Soluble oil has its lubricity due to oil emulsion [20].The viscosity of water diluted soluble oil is almost equal to that of water, so the hydrodynamic lubrication is negligible compared to straight oils. Lubricant additives are added to increase their lubricity. The cutting fluid has good lubricity if it has high viscosity. Dynamic viscosity of conventional and nanocutting fluids with different wt. % of nanographite is measured using ASTM D2983 using Brookfield Viscometer [21].The equipment was initially checked for accuracy by measuring the dynamic viscosity of distill water at room temperature thrice. The average value of viscosity 1.02 cP was very close to the actual value 1 cP. The measurement error was found to be 2%. After ensuring the accuracy of the equipment, dynamic viscosity of conventional, and nanocutting fluids with different wt. % of nanographite is measured. ###### Machining Performance Evaluation. Experiments are performed on Lathe by turning AISI1040 using cemented carbide tool in dry machining; flood machining, MQCL application of conventional cutting fluid and MQCL application of nanocutting fluids. Experiments are conducted at different flow rates and at different wt. % of nanocutting fluids to find their relative advantage on machining. Machining performance is evaluated by measuring the cutting forces, maximum flank wear, surface roughness, and examining the color and shape of chip. Cutting forces are recorded with Kistler Piezoelectric dynamometer [22] upto 15 min. The maximum flank wear (VB) is determined by direct measurement [23] at different intervals upto 33 min using Metallurgical Microscope. Surface roughness is measured using Surftest SJ-301 [24] at the end of machining. Surface roughness is measured at three different locations and average of the values is considered. Temperatures near the cutting zone are measured by using embedded tool thermocouple. The chips are collected for all conditions and are visually examined and their shape and color are noted. A regression model is developed to estimate the tool wear for nanocutting fluid. All experiments are conducted in triplicate and average of the values is taken. ###### Environmental Effect Evaluation. The effect of nanocutting fluids on the environment if it is disposed to water resources is predicted using BOD5 and COD analysis. BOD analysis is an empirical test in which standardized laboratory procedures are used to determine the relative oxygen consumed for the biochemical degradation of organic material, to carbon-dioxide and water, in wastewater effluents and polluted waters (Eq. (1)) [25]Display Formula (1)$CnHaObNc+(n+a4-b2-34c)O2→Bacteria→nCO2+(a2-34C)H2O+cNH3$ BOD5 is the measurement of oxygen consumed in a 5-day test period. Activated sludge from a waste water treatment plant is used as inoculum. Nutrient, buffering system, and inoculum are added to distill water and are aerated. BOD bottles are filled with this aerated water and 0.1 ml of sample is added to it. BOD bottles are taken in triplicate for each sample. Samples are incubated in incubator for 5 days. Dissolved oxygen (DO) is measured using Winkler's method [24]. BOD5 is evaluated using the following equation:Display Formula (2)$BOD=[(DO0-DO5)-(C0-C5)]×(Volume of Bottle)(Volume of Sample)$ where DO0 is DO of the sample at time t = 0, DO5 is DO of the sample at time t = 5th day, C0 is DO of distill water (blank) at time t = 0, and C5 is DO of distill water at time t = 5th day. COD is the amount of dissolved oxygen required to oxidize and stabilize organic and inorganic content of the sample solution [25]. This test is extensively used in analysis of industrial wastes, particularly in surveys designed to determine and control losses to sewer system. The oxygen equivalent is measured by refluxing the diluted sample using potassium dichromate in an acidic medium (sulphuric acid) and by titrating with ferrous ammonium sulphate (FAS) solution. COD of samples are determined using the following equation:Display Formula (3)$COD(A-B)×normality of FAS ×8×1000Quantity of Sample$ where A is quantity of FAS added to the Blank and B is quantity of FAS added to the sample. Biodegradability index (BI) is the ratio of BOD5 and COD [26]. It is used to check the readily biodegradability of a sample. If BI > 0.6, then the waste is fairly biodegradable and can be effectively treated biologically. If 0.3 < BI < 0.6, then seeding is required to treat it biologically. If BI < 0.3, it cannot be treated biologically, i.e., they should be properly treated prior to disposal to the environment. ###### Economic Aspect of MQCL Application of Nanocutting Fluids. Results from experimentation are used to evaluate the economic aspect of nanocutting fluids. Maximum cutting forces developed during machining is used to determine power consumed. Tool wear at the end of machining is used to estimate tool life and the number of tools consumed/year, which gives the cost spent on tools. The cost for oils, tools, power consumption, etc., as in India is considered and is mentioned in equivalent US dollars. Following are the assumptions considered for economic evaluation of cutting fluids: 1. (1)One machine with a 120 l sump, 12 l/day is added, based on an average of 12.5% makeup per day [27]. 2. (2)Unmanaged machine coolant is changed after 3 weeks and managed machine coolant is changed after 6 weeks [28]. Considering average, coolant is changed every month, i.e., after 4.5 weeks. 3. (3)Machine coolant cost at MAK SHEROL B—( 4500/20 l)—$71.74/20 l [29].
4. (4)Cost of cemented carbide tool bit with four cutting edges—( 541/insert)—$8.62 (based on quotation from Sandvik Coromant). 5. (5)Sump has to be cleaned and machine coolant is mixed about 20:1. It costs about (Labor cost/day— 115)$1.83 to clean and charge a sump after each change.
6. (6)Cost of water—( 515/5000 l)—$8.211/5000 l [30] 7. (7)Cost of nanographite powder in Bulk—( 83.79/g)—$1.336/g (based on quotation from EPRUI Nanoparticles & Microspheres Co., Ltd.:$1336/kg). 8. (8)Cost of functionalizing nanographite powder—( 9.09/g)-$ 0.145/g (calculated based on cost of chemicals consumed and power consumed during functionalization, is shown in Table 3Table 3

Cost of functionalization/gram

For functionalizing 70 g nanopowder/day, i.e., 1820 g/monthCost of consumables used/month (P)6 M Sulphuric acid and 6 M nitric acid are used for functionalization (P)Amount consumed/monthCost/monthSulphuric acid costs ($2.56/500 ml) (Qualigens 2013 price list)24.5 l$ 125.84Nitric acid cost ($2.51/500 ml) (Qualigens 2013 price list)13.9 l$ 70Water consumed cost ($8.211/5000 l)148.78 l$ 0.244Total consumables cost$196.08Power consumed for functionalization in a month (Q)Power consumed/monthCost/monthRefluxing for 6 h (600 W)6 h × 600 W × 26 days = 93.6 kWh$ 9.24Filtration for 6 h (0.25 kW)6 h × 0.25 kW × 26 = 39 kWh$3.85Drying for 18 h (1.2 kW) (Suppose samples are dried weekly)18 h × 1.2 kW × 4.3 weeks = 92.88 kWh$ 9.17Total cost of power consumed225.48 kWh$22.27Labor cost ($1.83/day) (R)$47.58Total amount spent for functionalizing 1820 g/month (P + Q + R)$ 265.93Total amount spent for functionalizing/gram$0.145/g). 9. (9)Disposal costs: Hazardous waste—( 12,000/metric ton)—$191.32/metric ton [31].
10. (10)Machining is performed 8 h/day, single shift, 6 working days/week using the considered process parameters.
11. (11)Cost of power consumption is based on retail supply tariffs for fy 2013–14 as per Andhra Pradesh Electricity Regulatory Commission for LT-III (Industrial)— 6.20/unit—\$ 0.0988/unit [32].

Total amount spent/year for machining (Ctotal) is calculated using the following equation:Display Formula

(4)$Ctotal=A+B+C$

where A = A1 + A2 + A3 + A4 + A5 + A6, B = (B1 + B2 + B3 + B4) × cost of power × 12, and C = C1 + C2.

• A = amount spent for procurement and disposal of oil, procurement, and surface treatment of nanopowder and water consumed/year

• A1 = cost of oil consumed/year

• A2 = cost of water used/year

• A3 = labor cost for cleaning the sump and charging of sump after each change/year (in case of flood lubrication)

• A4 = cost of nanographite consumed/year

• A5 = cost of surface treatment of nanographite/year

• A6 = cost of disposal of used cutting fluid/year

• B = cost of power consumed/year

• B1 = power consumed (kWh) by Lathe/month

• B2 = power consumed by pump/month

• B3 = power consumed by compressor/month

• B4 = power consumed by sonicator/month

• C = amount spent on tools/year

• C1 = cost of tools used/year = y × N

• C2 = cost of regrinding/year = x × N

• N = number of tool changes = (Tac/T)

• Tac = actual cutting time

• T = tool life

• x = cost of regrinding

• y = cost of insert/number of cutting edges (cemented carbide tool)

•     = cost of tool/(number of resharpening + 1) (HSS)

## Results and Discussion

###### Viscosity Measurement.

Figure 3 shows the dynamic viscosity for cutting fluids at different temperatures. It is found that viscosity increased with increase in concentration of nanographite. At room temperature, viscosity was found to increase by ≈2.7%, ≈7.9%, and ≈13% with respect to base cutting fluid due to inclusion of 0.1 wt. %, 0.3 wt. %, and 0.5 wt. % nanographite, respectively. This increase in viscosity was expected because, as more nanoparticles are included in the base fluid, the fluid offers more resistance and hence the torque required to turn the spindle also increases. This increased viscosity may increase the lubricity of the cutting fluid. Viscosity was found to decrease with increase in temperature for all samples.

###### Machining Performance.

Machining performance of nanocutting fluids is evaluated by the measurement of cutting forces, tool wear, surface roughness and by studying the chip morphology.

###### Cutting Forces.

Knowledge of the forces is needed for estimation of power requirements and for the design of machine tool elements, tool-holders and fixtures, to make the system rigid and free from vibration. Feed force, thrust force and main cutting forces obtained from dynamometer are used to find the resultant cutting force for all cutting conditions. Figures 4–6 show the variation of resultant cutting force (Fr) with respect to machining time at different flow rates 5 ml/min, 10 ml/min, 15 ml/min, respectively.

For all flow rates, cutting force was found to decrease with increase in concentration of nanographite. This may be due to the lubricating properties of nanographite which may have reduced the frictional forces between the tool and chip, which in turn reduced the resultant cutting forces. At flow rate 5 ml/min, cutting force is found to be least with 0.5 wt. % followed by flood cooling and 0.3 wt. %. MQCL application with conventional cutting fluid and 0.1 wt. % nanocutting fluid showed more cutting forces compared to flood cooling. In these cases, may be quantity of cutting fluid was not sufficient to provide adequate lubrication. At flow rates 10 ml/min and 15 ml/min, MQCL application with conventional cutting fluid and nanocutting fluid has reduced cutting forces compared to flood lubrication. In flood lubrication, where cutting fluid is applied as bulk, may be could not penetrate the interfaces causing insufficient cooling and lubrication.

###### Tool Wear.

Tool wear at the end of 33 min of machining is measured using Metallurgical Microscope. Figure 7 shows the variation of tool wear at the end of machining for all conditions. Table 4 shows the tool wear photo for all machining conditions with cemented carbide at 10× at the end of machining. MQCL application has caused tool wear to decrease with respect to dry and flood lubrication. The reason behind this may be the effective penetration of coolant at the interfaces causing reduction in the temperature leading to reduction in abrasive wear. Tool wear also decreased with nanocutting fluids. This decrease may be due to presence of nanographite which may have provided additional lubricating properties to the cutting fluids, causing reduction in friction at the interfaces, leading to reduced cutting forces and tool wear. Table 5 shows the percentage decrease in tool wear with respect to flood machining.

###### Surface Roughness.

During machining operations, new surfaces are generated through plastic deformation and crack propagation. Work piece is subjected to intense mechanical stresses and localized heating by the tool. The cutting edge leaves its mark on the surface. Surface finish is an important parameter because performance and service life of the machined component are affected by it. Figure 8 shows the variation of surface roughness under different cutting environments. The surface roughness was found to decrease with increase in MQCL flow rate. The flow rate was increased from 5 ml/min to 10 ml/min to 15 ml/min by increasing the air pressure which caused effective aerosol generation, which in turn led to efficient penetration of the fluid into the cutting region causing better cooling of chip tool interface temperature and reduced tool wear. This may be the reason for decrease in surface roughness with increase in mist flow rate. The surface roughness was also found to decrease with increase in percentage of nanographite in soluble oil. This may be due to the additional lubrication provided by the inclusion of nanographite in soluble oil. Table 5 shows the percentage decrease in surface roughness with respect to flood machining.

###### Cutting Temperature.

Figure 9 shows the variation of maximum temperature generated near cutting zone under different cutting environments. The temperature generated was found to decrease with increase in MQCL flow rate. The flow rate was increased by increasing air pressure. This increased the velocity of air coming out from nozzle and also atomized the oil droplets effectively, causing better cooling. Cutting temperature was also found to decrease with increase in concentration of nanographite. This may be due to enhanced thermal conductivity of the cutting fluid with inclusion of nanographite.

###### Chip Formation.

The shape, color and thickness of chips obtained during machining process gives a lot of information regarding the performance of the machine tool, parameters, and quality of the product. It is possible to control turning costs, tool life, and surface finish, leading to better economics if one masters in chip reading. Table 6 shows the shape and color of chips. The shape of chips obtained is same, i.e., curl with all lubricating conditions. The color, however, showed variation with cutting environment. The chips obtained under dry condition are blue in color indicating high chip tool interface temperature. The color of chips has changed from blue to golden to silver depending on the cutting condition (dry/flood/mist with and without nanographite). This change in color is due to reduction in chip tool interface temperature. MQCL application with cutting fluid at 5 ml/min, 10 ml/min, and 15 ml/min showed chip color variation from golden to light golden showing reduction in chip interface temperature with increase in flow rate. At 5 ml/min, chips are golden colored with conventional cutting fluid and combination of golden silver chips with nanocutting fluid. This represents that mist application at 5 ml/min with nanographite reduced the chip tool interface temperature effectively than without nanographite at the same flow rate but not as effectively as flood cooling which produced silver chips. At 10 ml/min and 15 ml/min, color of chips is light golden with conventional cutting fluid and silver colored with 0.1 wt. % and silver colored with shining with 0.3 wt. % and 0.5 wt. %.The color change clearly indicate the decrease in temperature at chip tool interface with increase in wt. % of nanographite. The shining appearance of the chips with 0.3 wt. % and 0.5 wt. % may be due to smooth finish of the chips due to reduced friction at chip tool interface caused by lubricating action of graphite nanoparticles. From the chip colors and shape, it can be concluded that the increase in flow rate of mist application and increase in wt. % of nanographite used in the cutting fluid has caused effecting removal of heat from chip tool interface.

Regression: Several models are reported in literature to predict tool wear; much of the work is contributed to dry machining [33-36]. Few models are reported on MQL application of cutting fluids [37,38]. Effect of nanocutting fluids on tool wear is seldom formulated. A mathematical regression model is built to estimate tool wear online for machining with nanocutting fluids (0.1 wt. %, 0.3 wt. %, 0.5 wt. %) applied at a flow rates of 5 ml/min, 10 ml/min, and 15 ml/min. Parameters like machining time, cutting forces, surface roughness, flow rate, wt. %, thermal conductivity of cutting fluid, cutting temperature, and dynamic viscosity are used to postulate the model. To reduce the number of variables involved in the model, dimensional analysis [39] is carried out and three nondimensional π terms are obtained

$π1=F×VBf×μπ2=F×SRf×μ×wt. %π3=t×F3μ3f2π4=k*f2*μ3*TF4$

where μ is dynamic viscosity of the fluids in Ns/m2, t is the machining time in seconds, SR is surface roughness in m, VB is maximum tool flank wear in m, F is cutting force in N, f is flow rate in m3/s, T is cutting temperature in Kelvin and k is thermal conductivity in W/mK. As the parameters are related nonlinearly, a relation $π1=k(π2)a(π3)b(π4)c$ is assumed. The relation is converted into linear relation by taking log of the π terms as log π1 = log k + a log π2 + b log π3 + c log π4. Multiple linear regression is performed using Minitab. The formulated model may be expressed as

$VB=1.07*10-5(t0.496SR0.343f0.107k0.221T0.221)(F0.053μ0.168wt. %0.343)$

An average regression coefficient of 0.97 is obtained. The proposed model is validated by comparing the predicted results with the experimental results in Fig. 10.

###### Environmental Evaluation.

BI of all samples is shown in Table 7. The results shows that the biodegradability indexes for all samples are less than 0.3, which implies that they cannot be treated biologically. So, they should be properly treated prior to disposal to the environment. The extent of biological oxidation ranged from 9% to 13% for nanocutting fluids as compared to 18% for soluble oil over the 5 day test period. This shows that biodegradability has decreased with inclusion of nanographite. Biodegradability decreases either due to presence of toxic materials in the sample which may prevent the microbial growth or due to presence of inorganic materials which is not degraded by microbes. According to material safety data sheet of procured nanographite, it is not toxic and has no negative ecological impact. The decrease in BI in this case is due to inorganic behavior of the selected nanoparticles, i.e., graphite. So, the proposed nanocutting fluid should not be used in flood lubrication where it has to be treated prior to disposal but should be used only in MQCL systems, where it is proposed to be applied in very small quantity preventing the need of disposal and reducing the burden on environment. Nanocutting fluids used in MQCL will help in maintaining clean and neat working area and prevent health problems due to heat and smoke and reduces burden on environment leading to ecofriendly, safe, clean cutting fluid.

###### Economic Evaluation.

Experimental data are used to evaluate economic performance of nanocutting fluids. Assumptions and method used to evaluate nanocutting fluid economically is mentioned in section 3.6. Total amount spent/year for machining (Ctotal) is calculated using Eq. (4). Total expenditure has been classified into three parts. First part consists of amount spent/year on oil (procurement + disposal), nanopowder (procurement and functionalizing), and water (A). Second part consists of amount spent for power consumption/year (B) and third part consists of amount spent on tools (C). Figures 11(a)11(c) show the amount spent for all these three parts while machining AISI1040 steel with cemented carbide tool. In case of dry machining, the amount spent for first part is zero and the amount spent for second part is the least, as it includes only power consumed during machining operation, as no external devices like pump/compressor is required. But the amount spent for third part is the highest, as the tools gets worn off frequently and need to be replaced with new tools. Figure 11(a) shows that the amount spent on part 1 increased drastically with increase in concentration of nanographite due to high cost of nanoparticles. If they are prepared in bulk, this cost may be reduced. The amount spent on part 1 also increased with increase in flow rate of nanocutting fluid. This is because; the increase in flow rate causes increases in consumption of cutting fluid and hence increases in consumption of nanoparticles. But 0.1 and 0.3 wt. % of nanocutting fluid at flow rate of 5 ml/min, 0.1 wt. % of at 10 ml/min and 15 ml/min are economical compared to flood lubrication with respect to amount spent on part 1. Figure 11(b) shows the amount spent on consumption of power. In case of dry machining, power is consumed only during machining operation. In flood machining, power is consumed by pump and machining operations. In case of MQCL application with conventional cutting fluid, power is consumed by compressor and machining operations and in case of MQCL with nanocutting fluids, power is consumed by compressor, sonicator and machining operations. Amount spent for power consumption is found to be least with dry machining. Power consumed during machining operations is calculated by multiplying the maximum cutting force generated with the cutting velocity. This information is used to determine power consumed in machining operations/year. This cost was found to decrease with increase in wt. % of nanographite and also with increase in flow rate, due to decrease in cutting forces. But, the overall amount spent for power consumption was more with nanocutting fluids due to use of more electrical components: compressor, sonicator. Figure 11(c) shows the amount spent on tools/year. It is highest in case of dry machining due to reduced tool life. Amount spent on tools for flood machining is more than in case of MQCL machining with and without nanoinclusions. Amount spent on tools decreased with increase in MQCL flow rates, due to decrease in tool wear. It also decreased with increase in concentration of nanographite for each flow rate, due to reduced tool wear. Figure 11(d) shows the total expenditure/year for machining operation for all cutting environments. Based on total expenditure on machining/year, MQCL with conventional cutting fluid was found to be economically best. MQCL at 5 ml/min with conventional and nanocutting fluids—0.1 wt. %, 0.3 wt. %, and 0.5 wt. %; MQCL at 10 ml/min and 15 ml/min with conventional cutting fluids and nanocutting fluids with 0.1 wt. % are found to be economic compared to flood and dry machining.

In overall economic analysis, labor cost contributes to a very minute quantity to the total cost. This is because of the low labor charges in India. In USA, UK, and Japan, labor cost is more. Thus, cost of functionalization of nanographite will increase, which in turn will increase the cost of using nanopowders. But, at the same time, in those countries, the cost of disposal of cutting fluid (hazardous waste) is also very high, which increases the cost of flood machining. So, the relative difference between costs involved in different cutting environments may remain same. Thus, a similar trend can be expected if the same analysis is done at USA, UK, and Japan.

## Conclusion

Cutting fluids with nanoinclusions are evaluated for its viscosity, machining performance, environmental effect, and economic aspect. Based on the present investigation, the following conclusions can be drawn:

1. (1)Dynamic viscosity of nanocutting fluid was found to increase with increase in concentration of nanographite, which may increase its lubricity.
2. (2)Nanocutting fluids applied as MQCL showed better machining performance compared to MQCL application with conventional cutting fluid, flood lubrication, and dry machining with respect to cutting forces, tool wear, cutting temperature, surface roughness, and chip shape and color.
3. (3)A regression model is developed for nanocutting fluids to estimate tool wear online when used in the range 0.1–0.5 wt. % at flow rates 5 ml/min–15 ml/min. The predicted model showed good agreement with experimental results.
4. (4)Biodegradability of nanocutting fluid has reduced with respect to conventional cutting fluid due to the inorganic nature of selected nanoparticles. So, the proposed nanocutting fluid should not be used in flood lubrication where it has to be treated prior to disposal but should be used only in MQCL systems.
5. (5)MQCL with conventional cutting fluids at all flow rates is found to be economically best.
6. (6)MQCL at 5 ml/min with conventional cutting fluid and nanocutting fluid with 0.1 wt. %, 0.3 wt. %, 0.5 wt. %; MQCL at 10 ml/min and 15 ml/min with conventional cutting fluid and nanocutting fluid with 0.1 wt. % are found to be economic compared to flood and dry machining.
7. (7)Among economic cutting fluids, optimum cutting fluid should be selected considering machining performance. MQCL application with conventional cutting fluid is most economic, but gives more surface roughness to the work piece compared to nanocutting fluid. MQCL with nanocutting fluid of 0.5 wt. % at 5 ml/min showed least surface roughness but is not economic with respect to conventional cutting fluid. So, a compromise has to be obtained between the economic and machinability aspects to choose an optimum cutting fluid.
8. (8)The work could be extended by performing machining at different cutting conditions by varying speed, feed, and depth of cut to study their effect when machining with nanocutting fluid. As the tool wear, cutting forces, and surface roughness has decreased with the inclusion of nanographite in the cutting fluid, nanocutting fluid is expected to perform well at higher speed, feed and depth of cut, thus increasing productivity.

## Acknowledgements

The authors are grateful to the Department of Industrial Production Engineering and Department of Mechanical Engineering, GITAM University, for providing the facilities to carry out the experiment. This work was supported by University Grants Commission (42-1070/2013(SR)) as Minor Research Project.

Abbreviations
• AISI =

American Iron and Steel Institute

• Al2O3 =

aluminium oxide

• ASTM =

American Society for Testing and Materials

• BI =

• BOD =

biological oxygen demand

• CaCl2 =

calcium chloride

• CNTs =

carbon nanotubes

• COD =

chemical oxygen demand

• FAS =

ferrous ammonium sulphate

• GPL =

graphene platelets

• HRC =

rockwell hardness

• HSS =

high speed steel

• IPMS =

intelligent prediction monitoring system

• MgSO4 =

magnesium sulphate

• MoS2 =

molybdenum disulphide

• MQCL =

minimum quantity cooling lubrication

• MQL =

minimum quantity lubrication

• MWF =

metal working fluid

• PBCM =

process based cost model

• PVD =

physical vapor deposition

• ROI =

return-on-investment

• TOC =

total organic carbon

## References

Astakhov, V. P., 2008, “Ecological Machining: Near Dry Machining,” Book Machining: Fundamentals and Recent Advances, Springer, London, pp. 195–223.
Shop Guide to Reduce the Waste of Metalworking Fluids, Institute of Advanced Manufacturing Sciences and Waste Reduction and Technology Transfer Foundation,
Skerlos, S. J., “Environmentally Conscious Manufacturing at the Machine Tool,” Prevention of Metalworking Fluid Pollution, John Wiley & Sons, Hoboken, NJ, pp. 95–122.
“Microlubrication in Metal Machining Operations,” Report No. 320-889-302, WMRC Reports.
Heisel, U., Lutz, M., Spath, D., Wassmer, R. A., and Walter, U., 1994, “Application of Minimum Quantity Cooling Lubrication Technology in Cutting Processes,” Prod. Eng., 2(1), pp. 49–54.
Yasir, A., Che Hassan, C. H., Jaharah, A. G., Nagi, H. E., Yanuar, B., and Gusri, A. I., 2009, “Machinalibilty of Ti-6Al-4V Under Dry and Near Dry Condition Using Carbide Tools,” Open Ind. Manuf. Eng. J., 2, pp. 1–9.
Wins, K. L. D., Varadarajan, A. S., and Ramamoorthy, B., 2010, “Optimization of Surface Milling of Hardened AISI4340 Steel With Minimal Fluid Application Using a High Velocity Narrow Pulsing Jet of Cutting Fluid.” Engineering, 2(10), pp. 793–801.
Khan, M. M. A., Mithu, M. A. H., and Dhar, N. R., 2009, “Effects of Minimum Quantity Lubrication on Turning AISI 9310 Alloy Steel Using Vegetable Oil-Based Cutting Fluid,” J. Mater. Process. Technol., 209(15), pp. 5573–5583.
Li, K. M., and Chou, S. Y., 2010, “Experimental Evaluation of Minimum Quantity Lubrication in Near Micro-Milling,” J. Mater. Process. Technol., 210(15), pp. 2163–2170.
Lee, P. H., Nam, J. S., Li, C., and Lee, S. W., 2012, “An Experimental Study on Micro-Grinding Process With Nanofluid Minimum Quantity Lubrication (MQL),” Int. J. Precis. Eng. Manuf., 13(3), pp. 331–338.
Nam, J. S., Lee, P. H., and Lee, S. W., 2011, “Experimental Characterization of Micro-Drilling Process Using Nanofluid Minimum Quantity Lubrication,” Int. J. Mach. Tools Manuf., 51(7), pp. 649–652.
Ewald, B., and Kwon, P. Y., 2011, “Effect of Nano-Enhanced Lubricant in Minimum Quantity Lubrication Balling Milling,” J. Tribol., 133, pp 1–8.
Shen, B., Malshe, A. P., Kalita, P., and Shih, A. J., 2008, “Performance of Novel MoS2 Nanoparticles Based Grinding Fluids in Minimum Quantity Lubrication Grinding,” Trans. NAMRI/SME, 36, pp. 357–364.
Mao, C., Tang, X., Zou, H., Huang, X., and Zhou, Z., 2012, “Investigation of Grinding Characteristic Using Nanofluid Minimum Quantity Lubrication,” Int. J. Precis. Eng. Manuf., 13(10), pp. 1745–1752.
Setti, D., Ghosh, S., and Rao, P. V., 2012, “Application of Nano Cutting Fluid Under Minimum Quantity Lubrication (MQL) Technique to Improve Grinding of Ti–6Al–4V Alloy,” Proceedings of World Academy of Science, Engineering and Technology (No. 70), World Academy of Science, Engineering and Technology, pp. 512–516.
Samuel, J., Rafiee, J., Dhiman, P., Yu, Z. Z., and Koratkar, N., 2011, “Graphene Colloidal Suspensions as High Performance Semi-Synthetic Metal-Working Fluids,” J. Phys. Chem. C, 115(8), pp. 3410–3415.
Gerulová, K., Amcha, P., and Filická, S., 2010, “Preliminary Ecotoxicity and Biodegradability Assessment of Metalworking Fluids,” Res. Papers Faculty Mater. Sci. Technol. Slovak Univ. Technol., 18(29), pp. 17–27.
Gannon, J. E., Onyekewlu, I. U., and Bennett, E. O., 1981, “BOD, COD and TOC Studies of Petroleum Base Cutting Fluids,” Water, Air, Soil Pollution, 16(1), pp. 67–71.
Sun, J. P., Li, X., Ng, R. S., Zhou, J. H., and Song, B., 2009, “Economic Impact Assessment of Intelligent Prediction Monitoring System (IPMS) for Real-Time Tracking of Machining Processes,” SIMTech Technical Reports (STR_V10_N4_11_STA), Vol. 10, No. 4.
Byers, J. P., 2006, Metalworking Fluids, CRC Press, Boca Raton, FL.
ASTM Standard D2983-03, 2004, Standard Test Method for Low-Temperature Viscosity of Lubricants Measured by Brookfield Viscometer, Book of Standards, 05.01, Petroleum Products and Lubricants, ASTM International.
Tschätsch, I. H., and Reichelt, D. I. A., 2009, “Cutting Force Measurement in Machining,” Applied Machining Technology, Springer, Berlin, pp. 353–359.
American National Standard, 1985, “Tool Life Testing With Sigle Point Turning Tools,” ANSI/ASME B94.55M-1985, ASME, New York.
ISO Standards, ISO 25178-701, “Geometrical Product Specifications (GPS)—Surface Texture: Areal Part 701: Calibration and Measurement Standards for Contact (Stylus) Instruments.”
Kotaiah, B., and Kumaraswamy, N., 1994, Environmental Engineering Laboratory Manual, Charotar Publishing House, Gujarat, India.
Srinivas, T., 2008, Environmental Biotechnology, New Age International, New Delhi, India, p. 10.
Institute of Advanced Manufacturing Sciences, Incorporated Machining Xcellence Division, “Pollution Prevention Guide to Using Metal Removal Fluids in Machining Operations,” p. 32.
Li, X., Lim, B. S., Zhou, J. H., Huang, S., Phua, S. J., Shaw, K. C., and Er, M. J., 2009, “Fuzzy Neural Network Modelling for Tool Wear Estimation in Dry Milling Operation,” Annual Conference of the Prognostics and Health Management Society.
Xuan-Truong, D., and Minh-Duc, T., 2013, “Effect of Cutting Condition on Tool Wear and Surface Roughness During Machining of Inconel 718,” Int. J. Adv. Eng. Technol., IV, pp. 108–112.
Krishna, V. P., Rao, D. N., and Srikant, R. R., 2009, “Predictive Modelling of Surface Roughness and Tool Wear in Solid Lubricant Assisted Turning of AISI 1040 Steel,” Proc. Inst. Mech. Eng., Part J, 223(6), pp. 929–934.
Luo, X., Cheng, K., Holt, R., and Liu, X., 2005, “Modeling Flank Wear of Carbide Tool Insert in Metal Cutting,” Wear, 259(7), pp. 1235–1240.
Fujiki, M., Ni, J., and Shih, A. J., 2009, “Investigation of the Effects of Electrode Orientation and Fluid Flow Rate in Near-Dry EDM Milling,” Int. J. Mach. Tools Manuf., 49(10), pp. 749–758.
Murthy, K. S., and Rajendran, I. G., 2012, “Prediction and Analysis of Multiple Quality Characteristics in Drilling Under Minimum Quantity Lubrication,” Proc. Inst. Mech. Eng., Part B, 226(6), pp. 1061–1070.
Douglas, J. F., Gasiorek, J. M., and Swaffield, J. A., Fluid Mechanics, 5th ed., Pearson Education, Ltd., Noida, India.
View article in PDF format.

## References

Astakhov, V. P., 2008, “Ecological Machining: Near Dry Machining,” Book Machining: Fundamentals and Recent Advances, Springer, London, pp. 195–223.
Shop Guide to Reduce the Waste of Metalworking Fluids, Institute of Advanced Manufacturing Sciences and Waste Reduction and Technology Transfer Foundation,
Skerlos, S. J., “Environmentally Conscious Manufacturing at the Machine Tool,” Prevention of Metalworking Fluid Pollution, John Wiley & Sons, Hoboken, NJ, pp. 95–122.
“Microlubrication in Metal Machining Operations,” Report No. 320-889-302, WMRC Reports.
Heisel, U., Lutz, M., Spath, D., Wassmer, R. A., and Walter, U., 1994, “Application of Minimum Quantity Cooling Lubrication Technology in Cutting Processes,” Prod. Eng., 2(1), pp. 49–54.
Yasir, A., Che Hassan, C. H., Jaharah, A. G., Nagi, H. E., Yanuar, B., and Gusri, A. I., 2009, “Machinalibilty of Ti-6Al-4V Under Dry and Near Dry Condition Using Carbide Tools,” Open Ind. Manuf. Eng. J., 2, pp. 1–9.
Wins, K. L. D., Varadarajan, A. S., and Ramamoorthy, B., 2010, “Optimization of Surface Milling of Hardened AISI4340 Steel With Minimal Fluid Application Using a High Velocity Narrow Pulsing Jet of Cutting Fluid.” Engineering, 2(10), pp. 793–801.
Khan, M. M. A., Mithu, M. A. H., and Dhar, N. R., 2009, “Effects of Minimum Quantity Lubrication on Turning AISI 9310 Alloy Steel Using Vegetable Oil-Based Cutting Fluid,” J. Mater. Process. Technol., 209(15), pp. 5573–5583.
Li, K. M., and Chou, S. Y., 2010, “Experimental Evaluation of Minimum Quantity Lubrication in Near Micro-Milling,” J. Mater. Process. Technol., 210(15), pp. 2163–2170.
Lee, P. H., Nam, J. S., Li, C., and Lee, S. W., 2012, “An Experimental Study on Micro-Grinding Process With Nanofluid Minimum Quantity Lubrication (MQL),” Int. J. Precis. Eng. Manuf., 13(3), pp. 331–338.
Nam, J. S., Lee, P. H., and Lee, S. W., 2011, “Experimental Characterization of Micro-Drilling Process Using Nanofluid Minimum Quantity Lubrication,” Int. J. Mach. Tools Manuf., 51(7), pp. 649–652.
Ewald, B., and Kwon, P. Y., 2011, “Effect of Nano-Enhanced Lubricant in Minimum Quantity Lubrication Balling Milling,” J. Tribol., 133, pp 1–8.
Shen, B., Malshe, A. P., Kalita, P., and Shih, A. J., 2008, “Performance of Novel MoS2 Nanoparticles Based Grinding Fluids in Minimum Quantity Lubrication Grinding,” Trans. NAMRI/SME, 36, pp. 357–364.
Mao, C., Tang, X., Zou, H., Huang, X., and Zhou, Z., 2012, “Investigation of Grinding Characteristic Using Nanofluid Minimum Quantity Lubrication,” Int. J. Precis. Eng. Manuf., 13(10), pp. 1745–1752.
Setti, D., Ghosh, S., and Rao, P. V., 2012, “Application of Nano Cutting Fluid Under Minimum Quantity Lubrication (MQL) Technique to Improve Grinding of Ti–6Al–4V Alloy,” Proceedings of World Academy of Science, Engineering and Technology (No. 70), World Academy of Science, Engineering and Technology, pp. 512–516.
Samuel, J., Rafiee, J., Dhiman, P., Yu, Z. Z., and Koratkar, N., 2011, “Graphene Colloidal Suspensions as High Performance Semi-Synthetic Metal-Working Fluids,” J. Phys. Chem. C, 115(8), pp. 3410–3415.
Gerulová, K., Amcha, P., and Filická, S., 2010, “Preliminary Ecotoxicity and Biodegradability Assessment of Metalworking Fluids,” Res. Papers Faculty Mater. Sci. Technol. Slovak Univ. Technol., 18(29), pp. 17–27.
Gannon, J. E., Onyekewlu, I. U., and Bennett, E. O., 1981, “BOD, COD and TOC Studies of Petroleum Base Cutting Fluids,” Water, Air, Soil Pollution, 16(1), pp. 67–71.
Sun, J. P., Li, X., Ng, R. S., Zhou, J. H., and Song, B., 2009, “Economic Impact Assessment of Intelligent Prediction Monitoring System (IPMS) for Real-Time Tracking of Machining Processes,” SIMTech Technical Reports (STR_V10_N4_11_STA), Vol. 10, No. 4.
Byers, J. P., 2006, Metalworking Fluids, CRC Press, Boca Raton, FL.
ASTM Standard D2983-03, 2004, Standard Test Method for Low-Temperature Viscosity of Lubricants Measured by Brookfield Viscometer, Book of Standards, 05.01, Petroleum Products and Lubricants, ASTM International.
Tschätsch, I. H., and Reichelt, D. I. A., 2009, “Cutting Force Measurement in Machining,” Applied Machining Technology, Springer, Berlin, pp. 353–359.
American National Standard, 1985, “Tool Life Testing With Sigle Point Turning Tools,” ANSI/ASME B94.55M-1985, ASME, New York.
ISO Standards, ISO 25178-701, “Geometrical Product Specifications (GPS)—Surface Texture: Areal Part 701: Calibration and Measurement Standards for Contact (Stylus) Instruments.”
Kotaiah, B., and Kumaraswamy, N., 1994, Environmental Engineering Laboratory Manual, Charotar Publishing House, Gujarat, India.
Srinivas, T., 2008, Environmental Biotechnology, New Age International, New Delhi, India, p. 10.
Institute of Advanced Manufacturing Sciences, Incorporated Machining Xcellence Division, “Pollution Prevention Guide to Using Metal Removal Fluids in Machining Operations,” p. 32.
Li, X., Lim, B. S., Zhou, J. H., Huang, S., Phua, S. J., Shaw, K. C., and Er, M. J., 2009, “Fuzzy Neural Network Modelling for Tool Wear Estimation in Dry Milling Operation,” Annual Conference of the Prognostics and Health Management Society.
Xuan-Truong, D., and Minh-Duc, T., 2013, “Effect of Cutting Condition on Tool Wear and Surface Roughness During Machining of Inconel 718,” Int. J. Adv. Eng. Technol., IV, pp. 108–112.
Krishna, V. P., Rao, D. N., and Srikant, R. R., 2009, “Predictive Modelling of Surface Roughness and Tool Wear in Solid Lubricant Assisted Turning of AISI 1040 Steel,” Proc. Inst. Mech. Eng., Part J, 223(6), pp. 929–934.
Luo, X., Cheng, K., Holt, R., and Liu, X., 2005, “Modeling Flank Wear of Carbide Tool Insert in Metal Cutting,” Wear, 259(7), pp. 1235–1240.
Fujiki, M., Ni, J., and Shih, A. J., 2009, “Investigation of the Effects of Electrode Orientation and Fluid Flow Rate in Near-Dry EDM Milling,” Int. J. Mach. Tools Manuf., 49(10), pp. 749–758.
Murthy, K. S., and Rajendran, I. G., 2012, “Prediction and Analysis of Multiple Quality Characteristics in Drilling Under Minimum Quantity Lubrication,” Proc. Inst. Mech. Eng., Part B, 226(6), pp. 1061–1070.
Douglas, J. F., Gasiorek, J. M., and Swaffield, J. A., Fluid Mechanics, 5th ed., Pearson Education, Ltd., Noida, India.

## Figures

Fig. 3

Variation of dynamic viscosity with temperature

Fig. 4

Variation of resultant cutting force with machining time at 5 ml/min

Fig. 5

Variation of resultant cutting force with machining time at 10 ml/min

Fig. 6

Variation of resultant cutting force with machining time at 15 ml/min

Fig. 7

Variation of tool wear at the end of machining

Fig. 8

Variation of surface roughness at the end of machining

Fig. 2

Schematic representation for mist generation

Fig. 1

Experimental set up

Fig. 9

Variation of maximum temperature near cutting zone

Fig. 10

Comparison between predicted and experimental results

Fig. 11

(a) Amount spent/year (Dollars) on oil, nanopowders and water, (b) amount spent/year (Dollars) on power consumption, (c) amount spent/year (Dollars) on tools, and (d) total expenditure/year (thousands of Dollars)

## Tables

Table 4 Tool wear photos at end of machining with cemented carbide
Table 5 Percentage decrease in tool wear and surface roughness with respect to flood machining
Table 2 Materials used for environmental evaluation
Table 1 Materials, equipments, and process parameters used for evaluating machinability characteristics
Table 6 Shape and color of chips
Table 7 BOD5, COD, and biodegradability index for all samples

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