A challenging study on compatibility or incompatibility of vegetable-based lubricant with human health

More than 70% of industrial lubricant waste releases into nature after a period of utilization without any �ltration stage. Knowing environmental concerns and increasing regulations over pollution, the request to use risk-free lubricant is irrefutable. One of these lubricants is vegetable-based cutting �uid (VBCF), which has recently attracted attention. The present work has tried to study the compatibility or incompatibility of VBCF with human health and provide a method for eliminating or reducing their potential risks. To achieve this goal, a study on one of the most known, destructive, and accessible microbes (Pseudomonas) in the workshop environment was performed. The results showed that Pseudomonas could multiply in solid and liquid mediums, and its colonies could quickly propagate in VBCF. Therefore, as a signi�cant achievement in this study, unreinforced VBCF is not a suitable selection from a health point of view. Although these cutting �uids are introduced as a compatible lubricant with humans and the environment, bacteria and mold can multiply swiftly without apparent alterations. It was also observed that using nanoparticles like copper-oxide with a speci�c volume fraction (0.4%) could �ght with the bio�lm of Pseudomonas to destroy the colonies at the initial time of their formation. Scanning Electron Microscope (SEM) images and Energy-Dispersive X-ray spectroscopy (EDX) analysis also studied the machinability attributes. The machining tests indicated that the nano�uid also greatly impacts the control of tool wear mechanisms and surface quality in A286 superalloy machining.


1-Introduction
Signi cant heat is produced during the machining of superalloys and other di cult-to-cut materials, drastically decreasing the tool life [1,2].Therefore, cutting uid (CF) is utilized to reduce the cutting temperature during the process [3,4].In general, cutting uid is applied to improve the e ciency and performance of cutting operations [5].The main advantages of cutting uid application are reducing the heat, increasing tool life, improving surface nish, preventing adhered-chip formation on the tool face (especially in alloys of which adhesive wear is the dominant mechanism), and facilitating chip removal of the cutting area [6].Though different CFs utilized in the machining industry, mineral-based cutting uids (MBCFs-approximately 85% of used oil) are the most widely used ones.Some scientists reported the worldwide consumption of 2.4 million tons of different cutting uids per year [7,8].Besides, the annual consumption of MBCFs in the European Union is around 320 thousand tons.Furthermore, more than twothirds of the used oils deliver to nature without a ltration process [9].However, the use of cutting uids creates some di culties and limitations, including environmental issues, operator health problems, as well as high costs (purchase and maintenance) due to unstable crude oil derivatives (approximately 17% of the total cost of cutting processes) [10,11].
In practice, all CFs utilized in machining industries are categorized into four classes: neat oil, soluble oil, semi-synthetic, and synthetic.In the case of the turning process, soluble oils are widely used, of which 85% are mineral-based.MBCF is naphthenic or para nic hydrocarbons derived from unstable crude oil [12].The IARC (1987) warned that MBCFs utilized in machining are carcinogenic.Recent studies have demonstrated high digestive, respiratory, and skin cancers in exposed populations and intensi ed numbers of cough and respiratory tract infections [12,14,15].In addition, some research has con rmed that occupational asthma problems stem from prolonged consumption of MBCFs [12].Furthermore, toxicity experiments have proved that some additives lead to cancer in lab animals.Nitrate particles used to prevent corrosion of cutting uids, for example, develop liver cancer.Also, medical studies indicate that MBCFs make up more than 80% of occupational skin diseases for machining operators.Some agents used as additives in the chemical composition of MBCFs are polyaromatic hydrocarbons (PAHs), long-chain aliphatic, sulfur compounds, nitrosamines, formaldehyde biocides, as well as formaldehyde-releasing biocides [16].Prolonged exposure to formaldehyde biocides and Polyaromatic hydrocarbons (direct contact with skin), and inhaling the produced gasses lead to skin and lung cancers [15].Also, diseases such as furunculosis, acne, occasional irritant reactions, folliculitis, and eczematous eruptions can happen very quickly.In addition, short-term inhalation or any contact with the generated vapor of the cutting uid can cause epitheliums, hyperpigmentation, and keratosis of the skin [12].
Therefore, from the viewpoint of safety and cost, replacement, removal, or even reduction of the cutting uid consumption is very important [17][18][19][20].Therefore, researchers proposed clean technology methods to solve MBCFs problems.As mentioned by Zhang et al. [21], to clarify the prevalent safety issues in the industrial environment and green manufacturing techniques for energy, they have tried to change the conventional lubrication method with the dry one that meets the nature patronage need as a vital processing technique.Therefore, dry-cutting processes are the rst choice for clean production.As mentioned by Dixit et al. [22], dry-cutting is de ned as an environment-compatible method without polluting water, air, soil, and other resources, reducing the production of waste and harmful substances.Controversially, the dry-cutting was more compatible than industrial one (conventional).As mentioned by Goindi and Sarkar [23], to remove perilous CFs during the cutting process, scholars have attempted machining without exerting CFs, also known as dry-turning.Besides, the processed chips under the dry method can be recycled without any cleaning operation, saving natural resources and reducing production costs.However, although dry cutting is the proper selection for implementing an environmentally friendly method, the tool wear rate is signi cant for some materials.
As mentioned by Krolczyk et al. [24], many studies have focused on enhancing cutting operations with a balanced attitude to reducing pollution produced by CFs.MQL/MQCL, cryogenic cooling, high-pressure assisted cooling, and VBCFs are the speci c areas of interest.The suggested technique of green manufacturing for the areas stated above includes the minimized usage of cutting uids and suitable cutting conditions, which causes to the diminution of the production cost, machining forces, and cutting temperature but enhancement of surface integrity, material removal rate, and prolongation of cutting tool consumption cycle.
As mentioned previously, some researchers have noted that VBCF, a compatible oil, is a potentially right choice compared to risky MBCF [25][26][27][28].Sani et al. [29] studied the in uence of VBCF on turning e ciency.Empirical tests con rmed that using VBCF resulted in green manufacturing and enhanced turning e ciency regarding tool failure and wear morphologies.Gajrani et al. [30] studied the in uence of VBCF on turning e ciency.The outcome revealed that feed force, cutting force, friction coe cient, and CLA roughness was diminished for VBCF compared with the other CFs.
Musavi et al. [31] evaluated the tribological behavior of VBCF in boundary layer situations by emphasizing the in uences of lubricant species on turning e ciency.In addition to higher environmental compatibility, they found higher tool life and surface integrity.Agrawal and Patil [32] conducted an experimental study of VBCF in machining.They have studied the in uences of CF on surface integrity and tool wear for VBCF and MBCF.They stated that VBCF led to lower surface roughness.However, the same surface quality was found for both VBCF and MBCF.Some scholars have studied the effects of vegetable-based oil with nanoparticles of CuO and SiO 2 to improve its applicability.Thottackkad et al. [33] added CuO nanoparticles to vegetable-based oil on a weight-percentage basis.They have investigated that the friction coe cient and tool wear were the lowest in optimal nanoparticle volume fraction.Das et al. [34] studied the performance of VBCF with Cuonanoparticles on machining e ciency in steel turning by the MQL technique.They stated that vegetable oilbased cuo-nanoparticles improved machining forces, wear mechanisms, surface quality, and chip topography.Shabgard et al. [35] investigated the tribological behavior of VBCF-based Cuo-nanoparticles in the grinding process.Their achievements reveal that the proposed nanoparticles help decrease the cutting force and temperatures, especially in the severe cutting situation.Furthermore, acceptable workpiece quality was found in all situations by applying the CuO nanoparticles as a CF.Sayuti et al. [36] added SiO 2 nanoparticles to the vegetable-based oil.Since less wear and better workpiece quality were the function objective of their research, the optimal amount of nanoparticle volume fraction and proper lubrication situations were studied.Their analyses proved that SiO 2 nano uid positively impacts the hard material's wear conditions and surface quality.Sharma et al. [37] evaluated the performance of silica-based CF in the machining process.Their results showed that silica-based CF could improve the machining e ciency regarding machining forces, workpiece quality, wear mechanisms, and chip topography compared with conventional CF.Although the effects of various VB nano uids on machining e ciency have been studied to a large extent, their anti-microbial properties have not been thoroughly investigated.
Given the rising attitude to the human and environmental challenges in the machining industry, the advances in compatible CFs have become a substantial duty.As an eco-friendly lubricant, vegetable-based one has gained a signi cant attitude.Though VBCF is more compatible with operators and the environment, bacteria and mold can quickly multiply without apparent alterations.The study's main aim is a risk assessment for different cutting uids and to provide alternative approaches with high-risk industrial methods in machining.Therefore, the possibility of a microbe's growth in vegetable-based oil as the safe cutting uid was studied.
For this reason, the culture of the speci c microbe under the name of Pseudomonas available in the workshop space was selected to risk assessment of CF.After identifying the microbial properties of the cutting uids, the controlling method of microbial growth has also been proposed.In the second part of the manuscript, machinability attributes (tool wear mechanisms and surface quality) of superalloy machining were studied to compare the machining performance of environmentally friendly cutting uid with conventional ones.

2-Materials and Equipment
The present study utilized different commercially available oils, including VB (eco-friendly) and MB (risky lubricant), as the CF.The VBCF was derived from olive, which can be appropriate for metal machining due to the high ash point.The MBCF was also derived from the para nic lubricant, categorized as unstable crude oil.The lubricant ingredients are the criterion for determining the safety or unsafety.Therefore, the chemical composition of both lubricants must be characterized.The composition of olive oil was characterized by gas chromatography analysis shown in Table 1.The MBCF compositions were analyzed by x-ray uorescence elemental analysis (XRF), as shown in Table 1.In addition, Table 2 displays the physical properties of the cutting uids.The cutting operation was also carried out on a solid rod of A286 superalloy using uncoated carbide inserts, SNMG-120404/ grade code GC1105. in machining processes stems from their tribological properties.Also, copper oxide's inherent antimicrobial properties and the silicon-oxide nanoparticles' Brownian solid motion (which provides good nanoparticle stability) have been the main reasons for selecting these particles.Furthermore, it seems that the amount of nanoparticles (volume fraction) in nano uid signi cantly affects microbial features of cutting uid.Therefore, different volume fractions from 0.1-0.4% were chosen for better comparison.Besides, for the proper investigation of the effect of low volume fraction on the colonization speed, the volume fraction of 0.05%, 0.1%, and 0.15% for SiO 2 was examined.Table 4 demonstrates the components of different environments for the microbial culture of Pseudomonas in nutrient and chocolate agar medium.When the stability of nanoparticles increased, the antibacterial properties of nano uid improved.Therefore, the prepared nano uid was ultrasonically suspended for 45 minutes to minimize the aggregation of nanoparticles.To better stabilize nanoparticles, the sonopuls-model GM3200 has been used to disperse them.This device had a probe that was entered into the tube test.Since the concentration of waves in this method was high, it provided excellent stability for nanoparticles.
In order to perform a microbial culture of Pseudomonas, the CF was placed in both test tubes and plates, as presented in Fig. 1.In addition to pure MBCF and VBCF, different nano uids and VBCF with antibacterial additives were used for better comparison, as shown in Fig. 1.The antibacterial was a liquid containing formaldehyde, with a volume percentage of 5%.This liquid was entirely soluble and did not require an additional process.

3-1-Microbial culture environment (medium)
Microbes must be located in an appropriate environment to multiply and generate separable colonies.
Therefore, the microbial culture can be a proper technique.The study utilized two different mediums for the microbial culture: nutrient agar and chocolate agar.

3-2-Pseudomonas
Pseudomonas is a member of the bacterial family, which is abundantly available in various resources.
Because the origin of the Pseudomonas is numerous in the workshop space, the evaluation of its growth situation is of crucial importance.
The microbial agent and lubricant were located in the tube and rotated at a 1200 rev/min speed.The sample was then moved to the incubator for one, three, and seven days at 37°C.The amount of nutrition supply for the colonies was su cient for more than four weeks, which did not cause the death of the colonies, and they will continue to grow.The criterion of the antibacterial properties of samples was the count of formed colonies.Therefore, the microscope observed the number of bacteria (big and small colonies), but the camera was used for full coverage of the sample surface.

4-1-Microbial culture tests
In part, to prove the presence of an antibacterial agent in MBCFs, Pseudomonas microbes have been cultivated in different CF mediums.MBCF (industrial CF) and VBCF (olive oil) were used for comparison.
According to the open literature, using VBCF is the rst solution for reducing the adverse effects of MBCFs.

4-1-1-Assessment of the effect of cutting uid type on antibacterial properties
Figure 2 demonstrates the overview images of the test plate after one and two days of microbial culturing inside the nutrient agar medium.There were no visible Pseudomonas colonies in Fig. 2. Since the colonies were tiny in the early days, the lack of visible colonies did not mean bacteria could not grow.Therefore, bacteria need more time to be visible.In other words, on the rst days, although microbes became multiply, the growth was not impressive, and the difference between samples was not clear to the naked eye.In sample 6, different regions are observable compared to other examples that are the product reaction of MBCF with water.The foam is produced like soap when the soluble lubricant is mixed with moisture in the agar medium.
Nevertheless, some Pseudomonas colonies became visible in several nutrient agar mediums after 72 hours of microbial culture in the controlled laboratory conditions.Figure 3 shows the overview images of samples 1-8 after three days of Pseudomonas culturing on a nutrient agar medium.The Pseudomonas in samples 4, 7, and 8 (arrows shown in Fig. 3), including pure VBCF, VBCF with 0.1% SiO 2 nanoparticles, and VBCF with 0.15% SiO 2 nanoparticles, respectively, can quickly grow.Since microbes can grow in this uid, they are not suitable for lubricant in the machining process, while many scholars introduce these oils as safe lubricants.Furthermore, due to the presence of a substance called Aminostofenin, the colonies had a speci c smell of grape or jasmine.Here, the question arises, why did Pseudomonas result in infection of the tissues?Pseudomonas has different pathogenic 1 agents, of which Exotoxin is the most important.
Exotoxin is a toxin released by a living bacterial cell into its surroundings, or it is a toxin secreted by bacteria.It acts as diphtheria and includes different amino acids 2 sprinkled using bacteria in space.As amino acid breaks from exotoxin, the toxin agent attaches to the cell receptor.After that, it arrives at the cell using endocytosis 3 , fractures there, and detaches from its receptor.Therefore, it enters the cytosol, resulting in the inactivation of protein synthesis and cell death.
Although many scholars declared that VBCFs were the safest CF for the operator's health [25][26][27][28], Fig. 3 proved that pure VBCF or reinforced VBCF with inappropriate nanoparticles were not suitable cutting uids.
Since the bacteria can quickly grow in VBCF without being visible, it is essential to do the test after a certain period (to avoid any mistake, which has been in some studies).As previously mentioned, due to the absence of antibacterial additives (harmful agents) in chemical composition, VBCF (unreinforced cutting uid) is inherently environment-friendly cutting uid, but when they are placed in infected environments (like a workshop where bacteria sources are abundant), they are rapidly infected and become dangerous.
Therefore, from the viewpoint of the human-friendly aspect, the statement of using unreinforced VBCF more than once or maintenance in the industrial environment is entirely wrong.
According to Fig. 3, samples 1, 2, 3, 5, and 6 present antibacterial properties that were the main purpose of the following research.As previously mentioned, the work aimed to present a technique for reducing the risk of cutting uid that has not been investigated by any researchers so far.However, according to the phenomenon seen in Fig. 2 (there were no visible or tiny colonies of Pseudomonas in the rst period), the lack of visible colonies did not mean bacteria could not grow, and it was possible that their antibacterial properties were not real.Therefore, more time has been given to the other samples to manifest their antimicrobial properties to achieve reliable results.Figure 4 represents the enlarged images of samples 1-8 after a week of the culturing of Pseudomonas in the nutrient agar medium.Although samples 2 and 5, including VBCF with 0.1% CuO and 0.4% SiO 2 nanoparticles, respectively, had antibacterial properties until three days, after a week, they could not maintain their properties, and bacterial colonies grown there.
Therefore, it can be concluded that any nanoparticle cannot have antibacterial properties (like SiO 2 nanoparticles).Moreover, the volume fraction of nanoparticles can sometimes be a critical factor in achieving the intended property (0.4% CuO nanoparticles).
According to the conducted experiments, samples 1, 3, and 6, including VBCF with 0.4% CuO nanoparticles, VBCF with antibacterial additive, and MBCF, respectively, present some antibacterial properties.Therefore, it has been proved that MBCFs have formerly antibacterial agents in their chemical compositions when synthesizing.As a result, their usage is not human and environment-friendly and should be replaced with suitable reinforced VBCF, as presented in sample 1.So now, why does the VBCF with 0.4% CuO nanoparticles have antimicrobial properties?First of all, the antibacterial activity must be de ned.This feature relates to compounds that locally kill any bacteria or delay the progress of their growth rate without being toxic to the surrounding substance.
Therefore, the initial requirement for having antibacterial properties was a delay in microbial growth.By this de nition, samples 2 and 5 had the initial requirement of antibacterial properties that was not enough.One of the signi cant shortcomings of samples 2 and 5 was their defeat to withstand the bacteria, which can generate bio lms.Bio lm is a strong virulence agent in Pseudomonas that presents a vital role in antibiotic resistance [39].It comprises microorganisms that cells attach mostly to the surface-this slimy cell is incorporated in a sticky extracellular matrix , which contains extracellular polymeric materials.A bio lm is an approach utilized using microorganisms to keep their health against external harmful agents and enhance their survival ability [40].However, increasing the CuO nanoparticles can surprisingly control bio lm activity and kill Pseudomonas.Since SiO 2 nanoparticles did not present su cient capacity to destroy the bio lm, they can not show antibacterial nature as they were exposed to the Pseudomonas bacteria.
The method used in the present work had good applicability.There are many works in that nanoparticles are added to the CF to increase machinability attributes such as increasing tool life, decreasing cutting force, and decreasing production cost.According to a new nding of the present study can conclude that using nano uid, in addition to achieving excellent process performance, signi cantly decreases the risk of cutting uid.Besides, this method has an easy preparation process and is affordable.This phenomenon showed the good practical applicability of the presented method in an industrial environment.

4-1-2-Assessment of the effect of nanoparticle volume fraction on antibacterial properties
Figure 5 presents the microscopic views of Pseudomonas colonies in sample 7 after one and three days.
Although no colony was seen on the rst day for sample 7 with the naked eye, Pseudomonas bacteria's presence was possible and visible.Furthermore, by comparing Fig. 5b with Fig. 5a, it was observable that silicon oxide nanoparticles with low volume fraction could not ght with the Pseudomonas, and the aggregation of Pseudomonas available in colonies signi cantly enhanced after three days.Therefore, in addition to the type of nanoparticles, their volume fraction can be another critical factor in preventing Pseudomonas bacteria's growth.
For the proper investigation of the effect of volume fractions of nanoparticles on the propagation rate of Pseudomonas bacteria, different amounts of volume fractions of SiO 2 were evaluated in chocolate agar medium.The medium has been changed from nutrient agar to chocolate to achieve more detail about the multiplication of Pseudomonas bacteria in the other environment.Figure 6 shows the images of the bacterial culture of Pseudomonas for VBCF with different volume fractions of SiO 2 nanoparticles, including 0.05%, 0.1%, and 0.15%.No colony was seen in any of the samples on the rst day.On the second day, the rst colony with small and bright shapes appeared in sample 1.It showed that SiO 2 nanoparticles with a 0.05% volume fraction could not ght with bio lm to destroy the colonies, while the intended bio lm was weak at the initial time of forming colonies.Samples 2 and 3, with 0.1% and 0.15% of nanoparticles, respectively, can achieve this result.Over time, the bio lm becomes strong, and colonies start nucleating in a medium with a higher volume fraction of SiO 2 nanoparticles.Noteworthy, although the starting time of the nucleation of the colonies for both mediums of nutrient agar and chocolate agar was the same, the pattern of progression of the colonies was not similar.In other words, in the nutrient agar, the colonies nucleate and extend, but in the chocolate agar, they nucleate and quickly distribute the whole sample becomes infected.Therefore, it can be concluded that the growth medium of the microbe can determine its growth mechanism.

4-1-3-Assessment of the microbial potential of used cutting uid after a cycle
The potential infectiousness of the cutting uid after use for a cycle in the machining process was also studied.Due to the presence of contamination sources in the workshop environment, as expected, the cutting uid quickly became infected.Although this phenomenon decreased the starting time of colonization, it led to faster contamination of the cutting uid.As a result, the pattern of colony progression has been completely changed.Figure 7 shows Pseudomonas's microbial culture for mineral and vegetablebased oils used in the machining industry after a cycle.As shown in Fig. 7a, microbial colonies (white points) grow in the VBCF medium (after 24 hours), while they can not grow in both mediums of MBCF.By comparing Fig. 7a with Fig. 2 and Fig. 6, the high rate of bacterial colonization is easily visible.This phenomenon shows that there are many Pseudomonas sources in the workshop environment.As previously observed, Pseudomonas cannot grow in the MBCF medium.Moreover, this can be attributed to the presence of antimicrobial agents such as formaldehyde biocides, polyaromatic hydrocarbons, and formaldehyde-releasing biocides in the MBCFs.Figure 7b represents the image of microbial culture in the VBCF medium for 12 hours that can observe the high speed of microbial growth.Figure 7c also shows the microbial culture in VBCF with 0.1% CuO nanoparticles after 24 hours that the microbe can hardly grow there.

4-2-Machinability tests
In the previous section, the compatibility or incompatibility of cutting uids with human health and the environment was studied in a laboratory condition, and an alternative technique was also introduced.Using suitable nanoparticles with an optimal volume percentage in the vegetable-base lubricant can be the right choice for replacing them with high-risk industrial ones.In this section, an attempt is made to study this modi ed cutting uid from the viewpoint of machinability aspects.

4-2-1-Tool wear morphology and surface chemistry
Tool wear morphology is the main machinability aspect [41,42].Therefore, novel research about the accurate conception of the in uences of nano uid-based lubricants on machining e ciency is asked.This phenomenon tends to enhance the parts' tool life and surface integrity [43].Abrasion, adhesion, and notch are the basic tool wear mechanisms.Among them, abrasion and adhesion are the main ones that emerge during superalloys machining and other high-toughness metals.Unfortunately, the adhesion mechanism can appear within a wide temperature domain; therefore, it is complicated to predict and control.The builtup edge (BUE) and built-up layer (BUL) are the most important subcategory of the adhesive wear phenomenon.
Figure 8 represents the SEM images of the tool rake face for A286 superalloy machining with conventional and reinforced vegetable-based cutting uids (nano uid).BUE and BUL are visible on the tool rake face under machining with conventional cutting uid.BUE is an accumulated workpiece material on the tool face close to the edge, which occupies the whole surface.BUE materials have impermanent nature that incrementally grows, fractures, and reforms.When BUE is squeezed into the tool-chip interface, the BUL appears.Therefore, BUL is approximately stable and is thoroughly adhered to the tool face.However, the existence of these materials on the tool rake face severely increases the friction, and if the lubrication conditions are not suitable, this layer is separated from the surface.It may also separate a wide part of the tool materials, which causes early failure of the tool.BUE, BUL (region inside the blue frame), detached BUL (regions inside the red frame), and removed tool material (the region with green arrow) are shown in Fig. 8a.BUL formation steps from BUE materials are schematically shown in Fig. 9.
In order to prove the nature of BUE and BUL, the chemical analysis of two different areas of the tool rake face was prepared.Figures 10 and 11 show the energy-dispersive X-ray spectroscopy (EDX) mapping analysis of the BUE surface (point 1) and the joint boundary between the BUL and the tool surface (point 2).The EDX mapping analysis of point 1 proves that the dominant agent is iron and nickel.Therefore, the material attached to the tool rake face is precisely the workpiece's material, and the BUE's nature is proven.The analysis of Fig. 11 also shows tungsten and iron elements with a speci c range in point 2.
Furthermore, the separation of BUL from the tool surface due to high tangential force and poor lubrication in the conventional cutting uid is visible in this analysis.BUE can create much worse conditions than the images presented in Fig. 8a.In other words, the area occupied by the BUE can be immensely vast, disrupting the cutting tool's mission for material removal and providing terrible surface integrity.These conditions depend entirely on the performance of the cutting uid.For example, Fig. 12 shows two SEM images with two different modes, including backscattered electron (BSE) and secondary electron (SE), for two different tools during superalloy machining using conventional cutting uid.
Figure 13 demonstrates an SEM image of the tool rake face, including three different regimes of tool wear mechanism and EDX analysis of the de ned points in Fig. 13.These three regimes consist of BUE, BUL (adhesion products), and abrasion wear mechanisms.Although regimes 2 and 3 have a similar appearance, chemical analysis of the surface shows the entirely different wear nature of these two areas.As a result, it can be concluded from the SEM images of the tool surface and its chemical analysis that the use of nano uid signi cantly affects the improvement of tool wear compared to the conventional cutting uid.Why the presence of these particles has a wonderful effect on the performance of the superalloy machining?
The role of nanoparticles in the cutting zone should be studied to answer the question.Figure 14 demonstrates the schematic of the nanoparticle's situation in the cutting zone.Therefore, tool wear reduction using nano uid can be interpreted by the phenomenon presented in Fig. 14.In a machining operation, since chip materials move away at a high-speed relative to the tool surface, this severe interaction causes to produce a high amount of heat.Nevertheless, nanoparticles in cutting uid result in the following four in uences, as shown in Fig. 14:

Rolling in uence
The abundant number of particles in a spherical shape and tiny scale in the cutting zone results in the particle acting as metal ball bearings.As a result, the removed materials (chips) quickly move away on the cutting tool surface.Therefore, the surface interaction between tool and chip or tool and workpiece surfaces is dramatically reduced.The produced heat is also diminished by eliminating the metal-metal surface's contact interaction.Hence, the tool life increases, and better cutting condition advances.

Protective in uence
Since the nanoparticles have a high surface area-to-volume ratio compared to the other materials, this agent desires to stick to each other, resulting in a gap at the tool-chip interface.

Mending in uence
Knowing that the initial surface of the workpiece contains many micron holes and its natural roughness, consequently friction coe cient is high.Therefore, the nanoparticles enter these holes and ll them, which leads to better surface integrity and a reduction in the friction coe cient and heat.

Polishing in uence
Because the used nanoparticles (CuO) are categorized in the oxide group, they have signi cant hardness and can act as an abrasive.Therefore, the nanoparticles polish the workpiece surface.
The four in uences mentioned above physically affect the cutting area.On the other hand, a solid phase, such as nanoparticles with a very high concentration, which has a better heat transfer coe cient than the liquid phase of the cutting uid, has improved the uid heat transfer conditions.Therefore, the heat exchanged by cutting uid with a workpiece or cutting tool enhances.

4-2-2-Surface integrity
In addition to the tool wear criterion, the quality of the machined surface can also be considered a tool to measure the performance of cutting uids [44,45].In xed machining conditions (cutting parameters, cutting tool materials), cutting uids that can provide better performance from the point of view of lubrication, cooling, and removing chip particles from the machining zone produce a better surface quality.In bad machining conditions, a large amount of chip material is temporarily welded to the cutting edge under BUE.As a result, the heat in the machining area signi cantly increases by passing a short period and according to the mechanical properties of superalloys [46,47].This issue leads to the phenomenon of thermal softening.Therefore, a volume of BUE material previously welded on the tool surface is separated and sticks to the workpiece's machined surface, dramatically affecting the natural surface roughness.This phenomenon is repeated intermittently and ruins the entire surface from the viewpoint of surface integrity.The proposed method in the current research is to reinforce the cutting uid using proper nanoparticles.Figure 15 presents the SEM image of the machined surface of superalloy using conventional lubricant and nano uid.As it is observable, the particles welded to the surface for machining with conventional cutting uid are visible.By using nano uid, this defect is wholly corrected, and the surface quality was greatly improved.
[1] In biology, a pathogen is anything that can create illness.
Its main agents consist of N, O, H, and C.
[3] Endocytosis introduces as a cellular function that materials are entered to the cell.

5-Conclusion
The study's main aim is a risk assessment for different cutting uids and to provide alternative approaches with high-risk industrial methods in the machining process.The main results of the work can be highlighted as follows: Due to the presence of the antibacterial agent in the chemical composition of industrial cutting uid, including formaldehyde biocides, polyaromatic hydrocarbons, and formaldehyde-releasing biocides, their usage is hazardous for human health.
According to the rapid colonization of Pseudomonas microbes in vegetable-based cutting uid when placed in the infected environments, this unreinforced cutting uid cannot be safe.
Since CuO nanoparticles can prevent the nucleation and progression of Pseudomonas colonies by destroying their bio lm, reinforced vegetable-based cutting uid with CuO nanoparticles exhibit excellent antibacterial properties.
The volume fraction of nanoparticles in nano uid can play a useful role in preventing the growth of Pseudomonas colonies.
Nano uid reinforced by nano CuO had good compatibility conditions and a signi cant effect on the machining performance of the superalloy cutting.In addition, the workpiece's tool wear and surface quality when using nano uid were signi cantly improved compared to the conventional cutting uid.Also, most importantly, since the bacteria can quickly grow in VBCF without being visible, it is crucial to do the test after a certain period to avoid any mistakes, which has been seen in some studies.Therefore, the statement of using VBCFs without reinforcing agents in the industrial environment, which many researchers have recommended using, is utterly wrong from the viewpoint of a green technology aspect.The Enlarged image of microbial culture medium after a week 1) VBCF with 0.4% CuO nanoparticles 2) VBCF with 0.1% CuO nanoparticles 3) VBCF with antibacterial additive 4) Pure VBCF 5) VBCF with 0.4% SiO2 nanoparticles 6) MBCF 7) VBCF with 0.1% SiO2 nanoparticles 8) VBCF with 0.15% SiO2 nanoparticles Figure 5 The microscopic view of the Pseudomonas after a) one and b) three days of microbial culture SEM image and X-ray spectroscopy of tool rake face

Figures
Figures

Figure 7 The
Figure 7 Figure 9

Table 1
CuO and SiO 2 nanoparticles, with 0.05, 0.1, 0.15, and 0.4 of vol%, were added to different CFs in the suspension state.Both are categorized in the oxide-solid group and cannot react with a neutral PH environment in a non-solid phase[38].Therefore, the proposed nanoparticles in the present work did not interact with the proposed oils.The density, morphology, dimension, and other mechanical properties of the CuO and SiO 2 nanoparticles are presented in Table3.The dramatic usage of CuO and SiO 2 nanoparticles

Table 3
Properties of CuO and SiO 2 nanoparticles

Table 4
The components of the sample in nutrient and chocolate agar medium Nutrient agar (Refer to Fig.2)Chocolate agar (Refer to Fig.5)