Green lubricants in action: a comprehensive performance evaluation of groundnut oil-based cutting fluids in metal machining processes

As industries worldwide seek environmentally sustainable solutions, the metalworking sector faces a growing need for eco-friendly alternatives to traditional cutting fluids. This abstract introduces the concept of an innovative approach to cutting fluid technology—the use of groundnut oil as a base material for machining fluids. Derived from peanuts, groundnut oil presents a renewable and biodegradable alternative to petroleum-based counterparts, addressing concerns related to resource depletion and environmental impact. A comprehensive performance evaluation of groundnut oil- based cutting fluid has been carried out by series of critical tests such as separation testing, particle size and stability testing, frictional testing, corrosion testing and drilling testing. The results of these tests collectively contribute to a comprehensive understanding of groundnut oil-based cutting fluids, shedding light on their potential as sustainable and high-performance alternatives in metalworking. The zeta potential for the prepared green cutting fluid has been found to be 49.10 mV. The dimensions of the dispersed particles in a fluid of the cutting fluid have been found as 250–260 nm. The environmentally friendly cutting fluid exhibits favourable outcomes in corrosion resistance, frictional performance, and drilling efficacy during testing.


Introduction
Cutting fluids play a pivotal role in metal cutting operations, offering a multitude of vital benefits that significantly enhance the efficiency, quality, and overall performance of the machining process.Cutting fluids serve as lubricants between the cutting tool and the workpiece, effectively minimizing friction.They are indispensable for optimizing metal cutting processes by delivering crucial functions such as lubrication, cooling, and efficient chip evacuation.Their contribution to prolonging tool life, refining surface finish, and augmenting overall machining efficiency underscores their paramount importance in contemporary metalworking practices.Consequently, cutting fluids, also referred to as metalworking fluids (MWFs), find extensive applications as both lubricants and coolants across various industries.Kumar and Ramamoorthy B [1] have reported that effective mitigation and the detrimental impacts of heat produced during machining can be determined by the type of cutting fluid used during the process.De Lacalle et al [2] have also concluded that MWFs are used to reduce the adverse effects of heat and friction on both the tool and workpiece.It has been reported that the European Union alone consumes around 320,000 tons of MWFs annually [3].Approximately 85% of the machining fluids employed worldwide consist of mineral oil-based cutting fluids (MOCF) [4].However, Abdalla et al (2007) [5] have suggested that a substantial proportion, comprising at least two-thirds, of these fluids necessitate environmentally responsible disposal.Though cutting fluids play a crucial role in metalworking processes, it's important to acknowledge that certain commercial cutting fluids can have potential adverse effects on the environment, health, and safety [6].Studies on work-related acquaintances to mineral oil indicate that production unit operations are at risk of encountering allergens and illnesses [7].To mitigate these adverse effects, there is a growing interest in the development and use of environmentally friendly cutting fluids, such as those based on bio-based oils like vegetable oils, which offer improved biodegradability, reduced toxicity, and lower environmental impact.Somashekaraiah et al (2016) [8] have reported that green cutting fluids prepared from renewable sources are highly less toxic, biodegradable, have low environmental pollution potential, and contribute to green and sustainable machining.Rahim and Sasahara [9] have assessed the effectiveness of artificial ester and essential tropical vegetable oil extracted from the fruit of oil palm trees as cutting fluids in minimum quantity lubrication (MQL) turning of GH169 alloy, particularly focusing on surface quality.Srinivas M S et al conducted the synthesis and testing of an innovative cutting fluid derived from neem oil, incorporating additives of ionic liquids [10].Belluco and Chiffre [11] have employed cutting fluids derived from rapeseed oil for the drilling of austenitic stainless steel.Zhao et al [12] emphasized the critical significance of minimum quantity lubrication (MQL)-assisted mechanical machining, particularly when handling challenging-to-cut alloys.In such cases, the cutting zone encounters heightened heat generation, given the greater energy demand inherent in machining processes involving materials of higher strength.Elmunafi et al [13] have investigated the application of castor oil as an emollient in the turning of hardened stainless-steel material, employing the MQL methodology.Ozcelik et al [14] have conducted a comparison between cutting fluids derived from sunflower and canola oils and traditional mineral oil in the machining process of AISI 304 austenitic stainless steel.The cutting fluid obtained from canola oil exhibited reduced tool wear when compared to its counterpart derived from sunflower oil.Ramana et al [15] have assessed three distinct conditions-dry cutting, palm oil application, and a combination of palm oil and boric acid lubricant-while turning Ti-6Al-4V alloy.Xavior and Adithan [16] have conducted an exploratory investigation to assess the influence of three distinct cutting fluids-coconut oil, straight cutting oil, and soluble oil-on surface finish and tool wear while turning AISI 304 austenitic stainless steel.In a study, Majak et al [17] examined the performance of AISI 304 stainless steel as the work material, with a focus on analyzing chip compression ratio and surface finish during MQL turning.They conducted experiments using three distinct vegetable oils: palm oil, sunflower oil, and coconut oil.
One such innovative and sustainable approach is the development and utilization of eco-friendly cutting fluids, with groundnut oil emerging as a promising base material.Groundnut oil, derived from peanuts, has gained attention for its renewable and biodegradable properties, making it an attractive candidate for the formulation of cutting fluids used in machining operations.The integration of eco-friendly cutting fluids into metalworking processes is a practical and impactful way for industries to contribute to the global sustainability agenda outlined in the SDGs.Research efforts are ongoing to optimize the formulation of groundnut oil-based cutting fluids, ensuring compatibility with various machining processes and materials.Onuoha et al [18] have investigated the effect of several vegetal oils, derived from groundnut and false walnut, along with industrial mineral oil on surface roughness of lathe machine turned AISI 1330 alloy.To assess the correlation between feed rate, depth of cut, and cutting speed on surface finish under various cutting fluids, statistical methods such as ANOVA and signal-to-noise ratio have been employed.Groundnut oil as the machining fluid found to provide superior surface roughness in turned parts.Saikiran and Kumar [19] have explored the capabilities of groundnut and cottonseed oils in the turning of copper alloy, utilizing a high-speed steel tool.The optimal process parameters have been determined to be a feed rate of 0.0916 mm/rev, spindle speed of 835 rpm, depth of cut of 1.5 mm, cutting speed of 80.89 m min −1 , and the utilization of groundnut oil.These parameters have been identified to adjust cutting circumstances, aiming for increasing MRR and surface finish while minimizing cutting forces.Ojolo et al [20] explored the wet turning of aluminum alloy, copper alloy, and mild steel using a tungsten carbide tool.The study assessed the influence of four oils-shea butter, coconut, palm kernel, and groundnut oils-on the cutting force during the machining process.Groundnut oil demonstrated the most significant reduction in cutting force during the machining of aluminum, particularly at specific feed rates and speeds.Bhowmik et al [21] have observed that machining with vegetable oil, particularly groundnut oil, resulted in a finer surface morphology compared to mineral oil.Groundnut oil exhibited superior lubricating ability, especially at higher temperatures, and generated the highest chip thickness among all vegetable oils (groundnut oil, neem oil and soya oil).The performance of different proportions of groundnut oil and camel milk as cutting fluid on Aluminum material has been evaluated for surface finish and tool life at various speeds and feeds during turning on a lathe machine by Samaila et al [22].The results showed that the higher feed rates tended to increase surface roughness.A combination of 80% camel and 20% groundnut oil resulting in a surface roughness of 522 μm at a spindle speed of 58 rpm and 11600 rpm cutting speed as revealed by the authors.The experimental study by Kumar and Ravi [23] focused on optimizing the machining process of EN-24-Steel using vegetable oil-based cutting fluids, such as cotton seed and groundnut oil, with different concentrations to improve surface roughness, tool life, and reduce toxicity compared to conventional fluids.The authors have investigated the input parameters such as speed, feed, and depth of cut, and output parameters including machining temperature, force, material removal rate (MRR), and surface roughness (SR).In another study, Silva et al [24] have assessed the viability of vegetable oils, such as soybean and corn, and their formulations as cutting fluids in grinding AISI 4340 steels.The authors have investigated the stability, favorable physicochemical properties, thermal stability, and superior performance of vegetable oils and compared them to mineral cutting fluids, highlighting their potential as eco-friendly, cost-efficient alternatives in industrial applications.Aguilar-Rosas et al [25] have investigated the use of sustainable materials in MWFs to achieve cleaner production processes.The authors aimed to produce and evaluate Pickering emulsions using Jatropha oil (JO) as the base and partially deacetylated and fibrillated chitin (PDFC) as the emulsifier at varying concentrations.Farfan-Cabrera et al [26] have produced microalgae oils as a promising solution for metalworking fluids (MWFs) used in MQL operations.The authors have explored the sustainability and eco-friendliness of microalgae oil-based metal working fluids.Farfan-Cabrera et al [27] have investigated the performance of aqueous nopal mucilage solutions as novel green metalworking fluids.The authors have studied their enhanced lubricity, thermal stability, and wear resistance.
The literature review highlights a discernible gap in research, indicating a limited exploration of the performance of cutting fluids based on groundnut oil.Prior research predominantly concentrated on examining the characteristics and performance of cutting fluids based on groundnut oil in machining operations.The implementation of these eco-friendly solutions requires collaboration between researchers, manufacturers, and regulatory bodies to establish industry standards and guidelines.The present manuscript introduces a thorough investigation into the performance of groundnut oil-based cutting fluids through a series of critical tests.The study encompasses separation testing, particle size and stability testing, frictional testing, corrosion testing, and drilling testing to provide a holistic understanding of the fluid's suitability for metalworking applications.This research not only addresses environmental considerations but also provides valuable insights for industries seeking efficient and eco-friendly solutions in the realm of cutting fluid technology.

Materials and methods
This section offers a comprehensive overview of the experimental setup, equipment, and procedures employed for each type of testing conducted to comprehensively evaluate the performance of the groundnut oil-based cutting fluid.The properties and fatty acid profile of groundnut oil is given in table 1 and table 2 respectively.The groundnut oil used in this work has been procured in its raw from the local market at Bengaluru, Karnataka, India.The hydrophilic-lipophilic balance (HLB) method has been employed to formulate a stable cutting fluid based on groundnut oil, tailored with the desired emulsion characteristics for optimal utilization in metalworking processes.This method is widely utilized to ascertain the equilibrium between hydrophilic (water-attracting) and lipophilic (oil-attracting) components in an emulsion, thereby guaranteeing the longevity of the formulation's stability.In the context of groundnut oil-based cutting fluids, this method is instrumental in assessing their ability to form and maintain stable emulsions for effective use in metalworking applications.The HLB method assigns a numerical value, known as the Hydrophilic-Lipophilic Balance, to surfactants or emulsifying agents.This value indicates the relative affinity of the agent for water or oil.The HLB scale ranges It is suitable for stabilizing water-in-oil emulsions.While Tween 20 is hydrophilic than lipophilic and suitable for stabilizing oil-in-water emulsions.The Griffin method was utilized to identify the suitable emulsifier for the base oil.Table 3 furnishes a comprehensive overview of the materials and methods utilized in the current study.The various methods and tests employed are discussed in subdivisions as follows.

Particle size and stability test
The optimal emulsion was determined through separation testing and stability assessment using dynamic light scattering equipment (DLS) (Model: 90 Plus Particle Size Analyzer, Manufacturer: Brookhaven Instruments Corporation), supplemented by physical examination.The DLS equipment was employed to determine both the particle sizes of the prepared emulsions and their zeta potential.Zeta potential, a measure of the electrostatic potential at the slipping plane of a particle in the fluid, was analysed as part of the characterization process.

Corrosion test
ASTM D4627 is a standard test method designed to evaluate the corrosion-preventing attributes of inhibited mineral oil when exposed to water.This method is applicable not only to mineral oils but also to cutting fluids, including groundnut oil-based variants, enabling the assessment of their corrosion inhibition capabilities.For this testing, mild steel chips were placed in a petri dish after ensuring they were dry.A piece of Whatman filter paper was positioned above the chips, followed by the addition of a small amount of the cutting fluids under investigation to cover the entire surface of the specimens.The function of the filter paper was to absorb any excess cutting fluid and create a humid environment, simulating conditions where cutting fluids may encounter water during machining.The container was then sealed and incubated for a specified period, typically 24 to 48 h, to allow for potential corrosion to occur.After the incubation period, the specimens and Whatman filter paper were visually inspected for signs of corrosion, such as rusting or discoloration.

Friction test
In this study, a tool chip tribometer was used, a sophisticated instrument designed for evaluating friction and wear properties, particularly within metal cutting or machining contexts.This tribometer was developed by Pottirayil et al and patented [28].To conduct our experiments, a high-speed steel (HSS) tool and a mild steel workpiece were mounted onto the tribometer.Before initiating the tests, the tribometer was accurately calibrated, a crucial step for obtaining reliable data.Next, the prepared cutting fluid based on groundnut oil was applied specially at the interface between the tool and workpiece.This step aimed to mimic real-world machining conditions as closely as possible.To replicate specific machining scenarios, carefully the machining parameters were set.These parameters play a significant role in determining the outcome of the tests and are essential for generating meaningful results.Following the completion of the tests, the coefficient of friction values was recorded.This data provides valuable insights into the frictional behaviour between the tool and workpiece under various conditions, contributing to a better understanding of the machining process.Figure 1 illustrates the schematic representation of the tool chip tribometer, offering a visual reference for the setup utilized in the experiments.

Drilling test
In the drilling experiments, two distinct workpiece materials: Aluminium and Mild steel were employed These materials offer valuable insights into the drilling process across varying substrates.To execute these experiments,  a conventional universal milling machine was utilized (Make: Hindustan Machine Tools' HMT FN2 model, renowned for its reliability and precision).For drilling, a 10 mm diameter high-speed steel (HSS) drill bit was utilized.To maintain consistency across experiments, the feed rate and the speed was set at 10 mm min −1 and 355 rpm respectively, in line with established parameters from literature [10].During the drilling operation the workpiece was submerged in cutting fluid throughout the process.To accurately measure the axial force exerted during drilling the Magnum Instruments drill dynamometer was employed.This device, equipped with a multichannel charge amplifier and data acquisition card, allows for precise recording of forces experienced during the drilling process.Such data is invaluable for understanding the forces involved and their impact on tool wear and workpiece integrity.The experimental setup, meticulously designed to capture relevant data, is depicted in figure 2. This illustration provides a visual representation of the configuration utilized in our study, aiding in the comprehension of our experimental methodology.

Separation testing
In the pursuit of sustainable and eco-friendly alternatives in metalworking processes, groundnut oil has emerged as a promising base material for cutting fluids.The successful application of groundnut oil in cutting fluids depends on its compatibility with various additives and the ability to maintain a stable formulation over time.This section delves into the crucial aspect of separation testing, a key evaluation method to assess the stability and effectiveness of groundnut oil-based cutting fluids.Separation testing plays a pivotal role in determining the stability of groundnut oil-based cutting fluids under the dynamic conditions of metalworking.This testing assesses the tendency of the formulation to separate into distinct phases over time, which could compromise its effectiveness and performance during machining operations.Several factors can influence the separation of groundnut oil-based cutting fluids, including temperature variations, exposure to contaminants, and the presence of incompatible additives.Understanding and mitigating these factors are essential for ensuring the longevity and reliability of the cutting fluid in industrial applications.Employing visual inspection and adjusting formulations based on observed instability represents a holistic strategy for attaining stability and optimization in groundnut oil-based cutting fluids.The Hydrophilic-Lipophilic Balance (HLB) method plays a pivotal role in this process by aiding in the selection of emulsifiers with suitable HLB values, essential for achieving a harmonious and enduring emulsion.Given that groundnut oil serves as the oil phase in the cutting fluid formulation, it necessitates emulsifiers to facilitate its dispersion in water effectively.Emulsifiers act as agents to stabilize the interface between oil and water, preventing phase separation and ensuring uniform distribution throughout the solution.By carefully selecting emulsifiers with appropriate HLB values, the formulation can be tailor to achieve the desired stability and performance characteristics.
After being kept in a hot air oven for 48 h to observe separation, the sample with an HLB value of 9 exhibits minor separation, as depicted in figure 3. Matching the HLB of the emulsifier to the required HLB for the base oil phase, such as groundnut oil, enhances the ability to create and maintain stable emulsions.This alignment ensures an optimal balance between hydrophilic and lipophilic properties, facilitating effective emulsion formation.However, samples with HLB values of 10.5 and 11 emonstrate significant separation after the same period.The distinct layers of differing colours indicate pronounced instability in these samples.

Particle size and stability
Particle size and stability are crucial factors in determining the effectiveness and performance of groundnut oilbased cutting fluids.Achieving the right particle size distribution and maintaining stability in the formulation are essential for optimal lubrication, cooling, and overall machining efficiency.The emulsification process plays a pivotal role in determining the particle size of the dispersed phase, such as groundnut oil droplets in water.Controlling this process is essential for achieving a uniform and fine particle size distribution, which contributes to stable emulsions.Zeta potential is the electrical potential at the slipping plane of a particle in a dispersion.It is a measure of the electrostatic repulsion or attraction between particles and is crucial for understanding the stability of colloidal systems.In the case of groundnut oil-based cutting fluids, which are typically emulsions of oil in water, zeta potential provides insights into the stability of the dispersed oil droplets.A higher zeta potential typically indicates greater electrostatic repulsion between particles, contributing to enhanced stability and resistance to coalescence or flocculation.
The particle sizes of the prepared emulsions and their zeta potential are measured using dynamic light scattering (DLS) equipment.The zeta potential is a measure of the electrostatic potential at the slipping plane of a particle in the fluid.The results showed that the zeta potential for the prepared green cutting fluid is 49.10 mV.This value of the zeta potential suggests that a relatively high level of electrostatic repulsion between particle, indicating a good stability and highly dispersed additives.Moreover, this value suggests that the stable cutting fluid enhances the lubrication, cooing efficiency, which in turn improves the machining performance.The particle size distribution or dimensions of the dispersed particles in a fluid of the cutting fluid has been found as 250-260 nm.Smaller particle sizes generally result in better lubrication properties.Fine droplets of groundnut oil provide improved coverage on cutting tools and workpieces, enhancing lubrication during machining processes and reducing friction and wear.The particle size distribution affects the cooling efficiency of the cutting fluid.Smaller droplets disperse more evenly and contribute to better heat dissipation during metalworking operations, preventing overheating and extending tool life.The zeta potential and particle size values for prepared green cutting fluid have shown similar pattern when compared with commercially available cutting fluid.The results of dynamic light scattering for the cutting fluids have been shown in figure 4. The similarity in Zeta potential and particle size between the prepared green cutting fluid (Groundnut oil-based cutting fluid) and the commercially available cutting fluid is an encouraging sign.It suggests that the prepared green cutting fluid has comparable stability and dispersion characteristics to the commercial cutting fluid.

Corrosion testing
Corrosion testing for cutting fluids is essential for ensuring the protection of metal components, maintaining tool and workpiece quality, promoting efficient machining processes, minimizing downtime, and addressing environmental and regulatory considerations.A robust cutting fluid should exhibit effective corrosion inhibition properties to meet the diverse requirements of metalworking applications.There are mainly three mechanisms involve in groundnut oil-based cutting fluids for protecting a work piece from corrosion, such as, barrier protection, passivation, neutralization of acidic components.Barrier protection is the process of developing a physical barrier over the metal surface for preventing the direct contact of the metal surface with moisture and atmospheric oxygen.The groundnut oil used in the study contains different fatty acids such as oleic acid, linoleic acid, palmitic acid, and stearic acid.All these fatty acids form stable complexes with metal ions and promotes the passive layer formation.This passive layers also protect a metal from corrosion.Different agents such as free fatty acids, phospholipids, tocopherols, proteins, and amino acids present in groundnut oil can change the pH level components present in the environment and neutralize the acidic component.This can aid the corrosion resistance capability of groundnut -based cutting fluid.Some challenges are there in this aspect as this is difficult to maintaining stability of bio-based cutting fluids over time, especially in industrial settings where cutting fluids are exposed to various contaminants and operating conditions such as under extreme temperatures or aggressive machining environments.Also, groundnut oil, like any natural resource, is subject to fluctuations in cost and availability.The corrosion inhibition property of groundnut oil-based cutting fluid has been investigated and result has been compared with deionized (DI) water and commercially available cutting fluids.Upon examination at 24 and 48 h, the specimen samples and Whatman filter papers yielded results depicted in figure 5. Notably, the utilization of groundnut oil as the cutting fluid prompted a noticeable change in the colour of the Whatman filter paper, turning it to a dark yellow hue.In contrast, there was no observable colour change when employing commercial cutting fluid or DI water.These findings suggest significantly elevated corrosion levels associated with the green cutting fluid compared to both the commercial cutting fluid and DI water.It is important to note that the green cutting fluid formulated in this study lacked any additives.Typically, additives in cutting fluids serve as corrosion inhibitors, forming protective layers on metal surfaces to mitigate or prevent corrosion.Hence, the observed heightened corrosivity indicates a need for incorporating eco-friendly additives into the green cutting fluid formulation to inhibit corrosion effectively.

Friction testing
In the context of evaluating the frictional characteristic of the cutting fluids, a tool chip tribometer has been used and simulated the conditions encountered during machining processes.After application of the prepared cutting fluid at the interface of tool and workpiece the coefficient of friction (CoF) for the tribo pair (tool-  shows more fluctuation compared to commercially available cutting fluid. he composition of groundnut oilbased cutting fluids may be more prone to changes over time, leading to variations in its lubricating properties.Commercially available cutting fluids often undergo rigorous formulation and quality control, which may result in more stable and consistent performance.Also, groundnut oil-based cutting fluids may be more sensitive to temperature variations, leading to fluctuations in viscosity and lubricating effectiveness.Temperature changes can influence the overall performance of cutting fluids.When the fluctuation over change in rotational speed has been observed CoF values are in higher side for lower value of rotational speed.At lower speeds, achieving proper lubrication between the tool and workpiece can be more challenging.There may not be enough relative motion between the tool and the workpiece to establish an effective cutting fluid film between them.This can result in a higher metal-to-metal contact and, consequently, higher friction.At lower rotational speeds mean that the cutting tool spends more time in contact with the workpiece, leading to increased heat generation.If the cutting fluid is not able to effectively dissipate this heat, it can lead to elevated temperatures at the interface, causing increased friction.The usage of the bio-oil leads to reduction in the tool-work interface temperature, and hence leads to reduced friction between workpiece and the tool.Also, this phenomenon leads to an improved surface finish.Low coefficient of friction results from change in shear rate by increase in sliding speed.The influence of tribo-film formed by bio-oil between tool and work leads to the improved tribological and machining performance.Similar results are also observed in the literature [29,30].This finding implies that groundnut oil-based fluids can effectively lubricate the cutting tool-workpiece interface, reducing friction and wear during machining operations, besides being cost-effective and environmentally benign.The findings of the study affirm the suitability of groundnut oil-based cutting fluids for machining operations, providing assurance to manufacturers and end-users regarding their performance and reliability.This validation encourages wider adoption of groundnut oil-based fluids and promotes confidence in their practical use.

Drilling test
Drilling tests for groundnut oil-based cutting fluids aim to evaluate their performance in metalworking applications, particularly during the drilling process.These tests assess the lubricating, cooling, and chip evacuation properties of the cutting fluid.When conducting drilling tests for groundnut oil-based cutting fluids, considering axial force (also known as thrust force or drilling force) is crucial for evaluating the lubricating and cooling properties of the cutting fluid.The axial force is the force exerted along the axis of the drill bit during the drilling process.Monitoring this force provides insights into the efficiency of the cutting fluid in reducing friction and facilitating chip evacuation.Each machining experiment is conducted for four different machining environments: dry, DI as cutting fluid, commercially available cutting fluid, and groundnut oil-based cutting fluid.The machining time is constant at 100 and 80 s while drilling Aluminium and Mild steel-based workpieces respectively.Figure 7 represents the data obtained from the dynamometer while conducting drilling operations.It was observed from figure 7 that dry machining gives the highest axial force.However, groundnut based cutting fluid showed a competitive result with commercially available cutting fluid.It suggests that the groundnut oilbased cutting fluid is providing improved lubrication and cooling during the drilling process.It forms a protective layer between the cutting tool and the workpiece, reducing friction and, subsequently, the axial force.

Conclusion
As industries strive to meet sustainability goals and reduce their environmental footprint, the adoption of groundnut oil-based cutting fluids represents a proactive step towards greener and more responsible metalworking practices.This manuscript sets the foundation for further exploration into the development, benefits, and challenges associated with this environmentally conscious approach in the field of cutting fluid technology greener and more responsible metalworking practices, aligning with global sustainability goals.From this work, the following conclusions can be derived.
1.The successful application of the HLB method in separation testing ensures that groundnut oil-based cutting fluids exhibit optimal stability, emulsion formation, and compatibility with additives.The sample with an HLB value of 9 visually shows the minor separation after 48 h of preparation.While the sample with HLB value 10.5 and 11 shows huge separation indicating insatiability.
2. The zeta potential value for the prepared green cutting fluid is found to be 49.10 mV.This value of the zeta potential suggests that a relatively high level of electrostatic repulsion between particle, indicating a good stability and highly dispersed additives.The particle size distribution or dimensions of the dispersed particles in a fluid of the cutting fluid has been found as 250-260 nm.Smaller particle sizes indicate in better lubrication properties of the groundnut oil-based cutting fluids.
3. When groundnut oil was utilized as the cutting fluid, the colour of the Whatman filter paper turned dark yellow, while there was no discernible alteration in the colour of the Whatman filter paper when commercial cutting fluid and DI water were employed.It can be inferred that the corrosion levels for green cutting fluid are very high compared to that of the commercial and DI water.Hence, it is suggested to incorporate the green corrosion inhibitive additives for the corrosion reduction.
4. The highest coefficient of friction (CoF) value observed for the groundnut oil-based cutting fluid prepared is 0.25, which closely resembles that of the commercially available cutting fluids.Groundnut-based cutting fluid and commercially available cutting fluid exhibit similar patterns for the coefficient of friction over time suggests that they share similar lubricating properties during the machining process.
5. The drilling performance of groundnut oil-based cutting fluids is rigorously evaluated through comprehensive drilling tests.Dry machining gives the highest axial force.However, groundnut based cutting fluid showed a competitive result with commercially available cutting fluid.It indicates that it could be a viable and effective alternative in machining applications, apart from being environment friendly.

Figure 4 .
Figure 4. Dynamic light scattering test results for green cutting fluid and commercial cutting fluid.

Figure 6 .
Figure 6.Variation of coefficient of friction with time for (a) groundnut oil-based and (b) commercial cutting fluid.

Figure 7 .
Figure 7. Variation of axial force with drilling time for (a) Aluminium and (b) Mild steel as work piece.
from 0 to 20, where lower values indicate a greater affinity for oil, and higher values indicate a greater affinity for water.De-ionized (DI) water and emulsifiers were blended in varying proportions with base oil (groundnut oil) to create emulsions.Various combinations of HLB values were formulated using emulsifiers with known HLB values.For this study, two distinct emulsifiers-Tween 20 and Span 40-were selected for investigation.Tween 20 is a polyoxymethylene sorbitan fatty acid ester.It is formed by the ethoxylation of sorbitan monolaurate.Specifically, it consists of a hydrophilic head group derived from polyethylene glycol (PEG) and a lipophilic tail derived from sorbitan monolaurate.Span 40 is a sorbitan fatty acid ester, specifically derived from the reaction of sorbitol with palmitic acid.It consists of a hydrophilic head group derived from sorbitol and a lipophilic tail derived from palmitic acid.Span 40 has a lower HLB value compared to Tween 20, indicating that it is more lipophilic.

Table 3 .
Examination of the utilized materials and methods.