OIL-FREE WATER-BASED CUTTING FLUID

Abstract

An oil-free water-based cutting fluid is disclosed. The cutting fluid comprises water, hexagonal boron nitride (hBN) particles, a dispersant, and a corrosion inhibitor. The hexagonal boron nitride (hBN) particles are hydrophilic particles having wettability in water. The hexagonal boron nitride (hBN) particle exhibits hydrophilicity solely through a heat-treatment synthesis process. The hexagonal boron nitride (hBN) particle exhibits hydrophilicity through dry surface treatment.

Claims

1. An oil-free water-based cutting fluid comprising: water; a hexagonal boron nitride (hBN) particle; a dispersant; and a corrosion inhibitor, wherein the hexagonal boron nitride (hBN) particle is a hydrophilic particle that is wettable with water.

2. The oil-free water-based cutting fluid of claim 1, wherein the hexagonal boron nitride (hBN) particle exhibits hydrophilicity solely through a heat-treatment synthesis process.

3. The oil-free water-based cutting fluid of claim 1, wherein the hexagonal boron nitride (hBN) particle exhibits hydrophilicity through dry surface treatment.

4. The oil-free water-based cutting fluid of claim 1, wherein the hexagonal boron nitride (hBN) particle has a primary particle size D50 in the range of 30 nm to 3 m and a primary particle size D90 of 5 m or less.

5. The oil-free water-based cutting fluid of claim 1, wherein the hexagonal boron nitride (hBN) particle is mixed in an amount of 0.1 parts by weight or less relative to 100 parts by weight of the water.

6. The oil-free water-based cutting fluid of claim 1, wherein the dispersant comprises one or more selected from the group consisting of an anionic dispersant, a cationic dispersant, a zwitterionic dispersant, and a nonionic dispersant, used alone or in combination.

7. The oil-free water-based cutting fluid of claim 1, further comprising one or more selected from the group consisting of a pH regulator, a defoaming agent, a preservative, an antifreezing agent, and a wetting agent.

8. The oil-free water-based cutting fluid of claim 1, further comprising one or more selected from the group consisting of Al.sub.2O.sub.3, MoS.sub.2, SiO.sub.2, ZrO.sub.2, CuO, SiC, TiO.sub.2, WS.sub.2, diamond powder, CNT, graphene, and graphite, wherein the Al.sub.2O.sub.3, MoS.sub.2, SiO.sub.2, ZrO.sub.2, CuO, SiC, TiO.sub.2, WS.sub.2, and diamond powder have a primary particle size D50 of 3 m or less.

9. The oil-free water-based cutting fluid of claim 1, wherein the cutting fluid is used in an MQL spraying method.

Description

DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is an electron microscope image showing the size of primary hexagonal boron nitride (hBN) particles used in Example 1;

[0030] FIG. 2 is a graph showing the particle size distribution of secondary hexagonal boron nitride (hBN) particles used in Examples 1 and 2, measured for a water-based cutting fluid processed using a high-pressure homogenizer;

[0031] FIG. 3 is a graph indicating the hydrophilicity of hexagonal boron nitride (hBN) particles subjected to a hydrophilic surface treatment process used in Example 2 and hBN particles without hydrophilic characteristics used in Comparative Example 1, as measured by FT-IR;

[0032] FIG. 4 is a photograph showing the dispersion appearance of a cutting fluid prepared using hBN particles with hydrophilic characteristics subjected to the surface treatment process of

[0033] Example 2, compared to a cutting fluid prepared using conventional hydrophobic hBN particles without hydrophilic characteristics used in Comparative Example 1;

[0034] FIG. 5 is a schematic diagram illustrating the end-mill milling method used to measure tool wear and surface roughness performance on SUS304 workpieces;

[0035] FIG. 6 is a graph showing the measured flank wear of an end-mill tool when using the cutting fluids applied in the Examples and Comparative Examples; and

[0036] FIG. 7 is a graph showing the surface roughness of SUS304 workpieces measured when using the cutting fluids applied in the Examples and Comparative Examples.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Hereinafter, specific examples in which the present disclosure can be implemented will be described in detail as examples. These examples are described in sufficient detail to enable those skilled in the art to practice the disclosure. It should be understood that the various examples of the disclosure are different from one another but are not necessarily mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in other examples without departing from the spirit and scope of the disclosure with respect to one example. Accordingly, the detailed description below is not intended to be taken in a limited sense. The scope of the disclosure is limited solely by the appended claims, together with all equivalents to which those claims, when properly described, are equivalent.

[0038] A water-based cutting fluid without oil according to an embodiment of the present disclosure comprises water, hexagonal boron nitride (hBN) particle, a dispersant, and a corrosion inhibitor, and is characterized by not containing any oil component. The hexagonal boron nitride (hBN) particles preferably possess hydrophilic characteristics such that they remain uniformly dispersed in the aqueous phase in a colloidal state for a prolonged period (at least 7 days).

Preparation of Hydrophilic Hexagonal Boron Nitride (hBN) Particles

[0039] Generally, hexagonal boron nitride (hBN) particles have hydrophobic surfaces and thus do not disperse well in water, either floating on the water surface or settling to the bottom, making them unsuitable for direct use as prepared by conventional methods.

[0040] Accordingly, in the present disclosure, it is preferable to use hBN particles that exhibit high hydrophilicity even without additional surface treatment, by synthesizing them in an air atmosphere without gas control, in which the synthesis is performed by using solid boron precursors and nitrogen precursors. The hexagonal boron nitride (hBN) particle is not synthesized by heat treatment in an inert atmosphere such as nitrogen or argon, which is a conventional preparation method. In this synthetic process, hydrophilicity is predicted to result from atomic-level defects on the particle surface, dangling bonds, surface oxidation, water molecule decomposition, and the resulting polar functional groups. More specifically, a boron precursor and a nitrogen precursor are mixed at a molar ratio of 1:1, and synthesis is performed in air at a temperature below 1600 C., for example, at 1500 C. for 3 hours, to obtain hydrophilic hBN particles, which are then washed and purified to yield a powder.

[0041] Alternatively, hydrophilic hBN particles can be prepared by surface-treating conventionally manufactured hydrophobic hBN particles to impart hydrophilicity. Any surface treatment method that imparts hydrophilicity may be employed without limitation.

[0042] For example, such hydrophilic surface treatments include wet chemical methods that induce defects under strongly acidic or strongly alkaline aqueous conditions. However, these wet treatments may leave toxic chemicals on the particles, increase processing costs, and introduce excessive chemical defects that can substantially damage the crystallinity of the hBN particles.

[0043] Dry surface treatment methods, in which the hBN particles are heat-treated in air or controlled gas atmospheres to induce polar groups on the particle surface, may be employed to impart hydrophilicity. Such dry treatments are preferred over wet methods because they create only the defects necessary to achieve hydrophilicity without excessive damage.

[0044] FIG. 1 is an electron microscope image showing the size of primary hBN particles, where the particle size refers to the size of single-crystal particles observed by scanning electron microscopy. FIG. 2 shows the size distribution of secondary hBN particles used in Examples 1 and 2, as measured for water-based cutting fluids processed with a high-pressure homogenizer. Here, the size of secondary particles refers to the particle size of aggregates of one or more primary particles measured by laser diffraction, with D10, D50, and D90 indicating particle size distribution parameters.

[0045] The hexagonal boron nitride (hBN) particle has a primary particle size D50 in a range of 30 nm to 3 m, more preferably 70 to 1 m, and most preferably 100 to 500 nm. In the case of a particle size D90, the particle size is in a range of 5 m or less. When hexagonal boron nitride (hBN) powder having a D50 of 30 nm or less is used, the particle morphology becomes nearly spherical, thereby reducing the lubricating effect attributable to exfoliation between sp.sup.2 layers. On the other hand, when hBN powder having a particle size of 3 m or more is used, sedimentation occurs due to gravity, resulting in poor dispersibility of the hBN particles in the aqueous cutting fluid. Consequently, concentration control of the hBN particles during machining becomes difficult, rendering the use of such powder unsuitable for cutting fluid applications.

Preparation of Water-Based Cutting Fluid

[0046] When the hydrophilic hexagonal boron nitride (hBN) powder prepared as described above is mechanically dispersed without the use of a dispersant, sedimentation occurs during long-term storage, making it difficult to maintain a uniform concentration of hBN. Accordingly, it is necessary to prepare an aqueous cutting fluid in which an appropriate dispersant is used at a weight ratio of not more than 1, based on 100 parts by weight of water (calculated as the solid content of the dispersant), so that more than 90% of the hBN particles remain suspended in a colloidal state without sedimentation even during long-term storage.

[0047] The water used in the aqueous cutting fluid according to one embodiment of the present invention may be appropriately selected from one or more of distilled water, deionized water, tap water, groundwater, and industrial water. In addition, the water may include electrolyzed ionized water having hydroxyl groups, which is alkaline ionized water with a pH of 10 or higher and is produced by electrolysis of water.

[0048] The dispersant is preferably a combination of an anionic polymeric dispersant and a nonionic polymeric dispersant; however, the invention is not limited thereto, and anionic, cationic, zwitterionic, or nonionic dispersants may be used alone or in combination.

[0049] Examples of the anionic dispersant include higher fatty acid salts, alkyl sulfonates, -olefin sulfonates, alkane sulfonates, alkylbenzene sulfonates, sulfosuccinate esters, alkyl sulfate esters, alkyl ether sulfate esters, alkyl phosphate esters, alkyl ether phosphate esters, alkyl ether carboxylates, -sulfonated fatty acid methyl esters, and methyltaurates. These anionic dispersants may be used alone or in combination of two or more thereof.

[0050] Examples of the nonionic dispersant include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, and glycerin fatty acid esters. In addition, certain nonionic dispersants, such as polyoxyethylene fatty acids and polyoxyethylene alkylamines containing anionic or cationic functional groups within the molecule, may exhibit anionic characteristics or cationic characteristics depending on the pH of the water while remaining nonionic. These nonionic dispersants may be used alone or in combination of two or more thereof.

[0051] In one embodiment, the aqueous cutting fluid according to the present invention comprises an anionic dispersant, wherein the hexagonal boron nitride (hBN) powder is included in an amount of 0.1 parts by weight or less based on 100 parts by weight of water, and the dispersant may be added in an amount of up to 1 part by weight or less (based on the solid content of the dispersant, corresponding to 10 g/L or less relative to the water volume) per 100 parts by weight of water. The amount of the dispersant may be appropriately selected in consideration of the dilution ratio in water and the content of hBN particles.

[0052] In another embodiment, the aqueous cutting fluid according to the present invention comprises a first dispersant, which is an anionic surfactant, and a second dispersant, which is a nonionic surfactant, such that two or more dispersants may be used in combination. The hexagonal boron nitride (hBN) powder is included in an amount of 0.1 parts by weight or less based on 100 parts by weight of water, and the weight ratio of the first dispersant to the second dispersant (first dispersant/second dispersant) may range from 1 to 9, preferably from 1 to 5, and more preferably from 1 to 3. The dispersants may be added in an amount of up to 1 part by weight or less (based on the solid content of the dispersant, corresponding to 10 g/L or less relative to the water volume) per 100 parts by weight of water. The amount of the dispersants may be appropriately selected in consideration of the dilution ratio in water and the content of hBN particles.

[0053] In one embodiment, the oil-free aqueous cutting fluid according to the present invention comprises a corrosion inhibitor to suppress corrosion of the metal workpiece and the machine tool. The type of the corrosion inhibitor is not particularly limited, and two or more corrosion inhibitors may be used in combination. The term corrosion inhibitor refers to an additive that primarily protects iron-containing metals or alloys thereof. The corrosion inhibitor may be incorporated in an amount of 0.2 to 3 parts by weight, preferably 0.3 to 2 parts by weight, and more preferably 0.5 to 1 part by weight, based on 100 parts by weight of deionized water in the corrosion inhibitor composition. When the amount is less than 0.2 parts by weight, effective corrosion inhibition is difficult to achieve, and when it exceeds 3 parts by weight, it may pose risks to human health and environmental safety. The corrosion inhibitor composition, comprising one or more of the above corrosion inhibitors alone or in combination with water, may be added to the aqueous cutting fluid in an amount not exceeding 30 parts by weight, preferably not exceeding 20 parts by weight, based on 100 parts by weight of the aqueous cutting fluid. The amount of the corrosion inhibitor composition may be further increased as the dilution ratio with water increases.

[0054] Thus, in the oil-free water-based cutting fluid according to one embodiment of the present invention, it is preferable to use hexagonal boron nitride (hBN) powder in an amount of 0.1 parts by weight or less based on 100 parts by weight of water, an appropriate dispersant in an amount of up to 1 part by weight or less (based on the solid content of the dispersant, corresponding to 10 g/L or less relative to the water volume) per 100 parts by weight of water, and a corrosion inhibitor in an amount of up to 10 parts by weight based on 100 parts by weight of water.

[0055] The content of the hexagonal boron nitride (hBN) particles may vary depending on the machining environment, such as the material and shape of the tool, the material of the workpiece, the machining method, the supply method, and the field of application, and, if necessary, the water-based cutting fluid may have a lower concentration of 0.01 parts by weight or less. When the content of the hBN particles exceeds 0.1 parts by weight, the cost relative to performance becomes significantly high. If the amount of the dispersant exceeds 1 part by weight (based on the solid content of the dispersant, corresponding to 10 g/L relative to the water volume) per 100 parts by weight of water, it may act as a foreign substance on the workpiece after machining. Moreover, if the amount of the corrosion inhibitor exceeds 10 parts by weight per 100 parts by weight of water, it may pose increased risks to human health.

[0056] Specifically, it is preferable to prepare the water-based cutting fluid by adding appropriate amounts of water, hydrophilic hexagonal boron nitride (hBN) particles, and a dispersant, and mixing the components, followed by dispersion treatment through homogenization using a high-pressure homogenizer or the like to produce a water-based suspension. Thereafter, a corrosion inhibitor is added and mixed to produce the cutting fluid.

[0057] In addition, the oil-free water-based cutting fluid according to one embodiment of the present invention may further comprise one or more components selected from the group consisting of a pH regulator, a defoaming agent, a preservative, an antifreezing agent, and a wetting agent. The mixing ratios and amounts of each of these components may be appropriately selected depending on the machining environment, the field of application, and the dilution of water used during the preparation of the cutting fluid.

[0058] When the water-based cutting fluid and the cutting fluid containing the same are used repeatedly in machining processes, microbial growth may occur, causing unpleasant odors. To prevent this, particularly in summer, a preservative may be additionally incorporated. Suitable preservatives include sodium benzoate, BIT (benzisothiazolinone) compounds, triazine compounds, benzotriazole compounds, tolyltriazole compounds, sodium benzoate used in food additives or cosmetics, zinc pyrithione, sodium pyrithione, and phenoxyethanol. Additionally, biocidal agents are not required, but compounds with good antimicrobial activity, such as alkylamines (having a carbon number of 10 or less), hexylene glycol, and antimicrobial nanoparticles of silver or copper, may be used alone or in combination of two or more. The preservative is preferably added in an amount of up to 1 part by weight based on 100 parts by weight of the water-based cutting fluid. The amount of the preservative may be further increased as the dilution ratio with water increases.

[0059] In addition, the oil-free water-based cutting fluid according to one embodiment of the present invention may further comprise one or more components selected from the group consisting of Al.sub.2O.sub.3, MoS.sub.2, SiO.sub.2, ZrO.sub.2, CuO, SiC, TiO.sub.2, WS.sub.2, and diamond powder. These components preferably have a primary particle size (D50) of 3 m or less. Furthermore, the cutting fluid may further comprise one or more components selected from the group consisting of CNTs, graphene, and graphite. These additional components serve to complement the lubricating mechanism inherent to the hexagonal boron nitride (hBN) particles.

Cutting Performance Test

[0060] The oil-free water-based cutting fluid according to one embodiment of the present invention, as described above, may be diluted with an appropriate amount of water in accordance with the usage environment or the machining purpose and used for metal machining. The amount of water for dilution is generally 5 to 50 times the volume of the cutting fluid, and the dilution ratio may vary depending on the machining environment, such as the material and shape of the tool, the material of the workpiece, the machining method, the supply method, and the field of application.

[0061] Hereinafter, a diluted cutting fluid was prepared by diluting the oil-free water-based cutting fluid according to one embodiment of the present invention tenfold with ordinary tap water, and the cutting performance was tested by preparing the following examples and comparative examples.

[0062] For use in the examples, a hydrophilic hexagonal boron nitride (hBN) powder having a particle size of 160 nm (D50) was prepared by mixing a boron precursor and a nitrogen precursor in a molar ratio of 1:1, performing heat treatment at 1500 C. for 3 hours in air without controlling the gas atmosphere, and subsequently cleaning and purifying the resulting product. In addition, a hydrophilic hexagonal boron nitride powder was prepared from a commercially obtained 1.4 m (D50) particle (without hydrophilic characteristics) by performing surface treatment through a dry method, involving heat treatment in air at 600-1500 C., to impart hydrophilicity.

[0063] For use in the comparative examples, a commercially obtained 1.4 m (D50) hydrophobic hBN powder (without hydrophilic characteristics), prepared by a conventional heat treatment method, was used. In addition, two conventional oil-containing O/W emulsion type water-soluble cutting fluids (from companies D and B) were prepared.

Example 1

[0064] 10 L of water, 10 g of the 160 nm (D50) hydrophilic hexagonal boron nitride (hBN) synthetic powder prepared as described above, and 100 g of a mixture of anionic and nonionic polymer dispersants were prepared. These components were mixed and subjected to dispersion using a high-pressure homogenizer by performing five low-pressure cycles at 7,000 psi and a flow rate of 0.1 L/min, followed by two high-pressure cycles at 15,000 psi, thereby producing a water-based suspension. A 1 L portion of the suspension was diluted with 10 L of tap water and 1 L of a corrosion inhibitor solution to prepare the cutting fluid. The resulting cutting fluid was supplied to an MQL (Minimum Quantity Lubrication) system and sprayed onto the machining area.

Example 2

[0065] 10 L of water, 10 g of the 1.4 m (D50) hBN powder subjected to dry surface treatment to impart hydrophilicity, and 100 g of a mixture of anionic and nonionic polymer dispersants were prepared. These components were mixed and subjected to dispersion using a high-pressure homogenizer by performing five low-pressure cycles at 7,000 psi with a flow rate of 0.1 L/min, followed by two high-pressure cycles at 15,000 psi, thereby producing a water-based suspension. A 1 L portion of the suspension was diluted with 10 L of tap water and 1 L of a corrosion inhibitor solution to prepare the cutting fluid. The resulting cutting fluid was supplied to an MQL (Minimum Quantity Lubrication) system and sprayed onto the machining area.

Comparative Example 1

[0066] 10 L of water, 10 g of the 1.4 m (D50) hydrophobic hBN powder without surface treatment, and 100 g of a mixture of anionic and nonionic polymer dispersants were prepared. These components were mixed and subjected to dispersion using a high-pressure homogenizer by performing five low-pressure cycles at 7,000 psi with a flow rate of 0.1 L/min, followed by two high-pressure cycles at 15,000 psi, thereby producing a water-based suspension. A 1 L portion of the suspension was diluted with 10 L of tap water and 1 L of a corrosion inhibitor solution to prepare the cutting fluid. The resulting cutting fluid was supplied to an MQL (Minimum Quantity Lubrication) system and sprayed onto the machining area.

Comparative Example 2

[0067] 1 L of a conventional oil-containing O/W emulsion type water-soluble cutting fluid (D Company, DP model) was portioned and diluted with 10 L of tap water to prepare the cutting fluid. The resulting cutting fluid was supplied to an MQL (Minimum Quantity Lubrication) system and sprayed onto the machining area.

Comparative Example 3

[0068] 1 L of a conventional oil-containing O/W emulsion type water-soluble cutting fluid (B Company, B9 model) was portioned and diluted with 10 L of tap water to prepare the cutting fluid. The resulting cutting fluid was supplied to an MQL (Minimum Quantity Lubrication) system and sprayed onto the machining area.

[0069] FIG. 3 is a graph showing the hydrophilicity of hexagonal boron nitride (hBN) particles having hydrophilic characteristics, obtained by performing the hydrophilic surface treatment process used in Example 2, and hBN particles without hydrophilic characteristics used in Comparative Example 1, as determined by FT-IR measurements, demonstrating that hydrophilic surface treatment can be achieved by dry surface treatment. FIG. 4 is a photograph showing the dispersion appearance of the cutting fluid prepared using hydrophilic hBN particles treated according to the hydrophilic surface treatment process of Example 2 and the cutting fluid prepared using conventional hydrophobic hBN particles without hydrophilic characteristics from Comparative Example 1.

[0070] First, the hBN particles in the cutting fluids of Examples 1 and 2 maintained a colloidal state even after storage for more than seven days. In contrast, in Comparative Example 1, sedimentation on the bottom of the container was visually observed after one day, as shown in FIG. 4.

[0071] FIG. 5 is a schematic illustrating the end-mill milling method used to measure tool wear and surface roughness performance on a SUS304 workpiece.

[0072] The milling machine used in the cutting performance test was a Doosan NX6500II machining center. The workpiece was SUS304 metal, sized 10010070 mm.sup.3, and the tool was a YG1 10 mm 4-flute end mill. Tool wear of the end mill was measured using a Keyence VHX5000, and the surface roughness of the machined workpiece was measured with a Mitutoyo SJ201. The cutting fluid was supplied to the machining area using a WINMIST MQL atomization system at a flow rate of less than 400 cc/hr. The milling cutting conditions were set as shown in Table 1.

TABLE-US-00001 TABLE 1 Parameter Condition Parameter Condition Cutting speed (m/min) 100 rpm 3,185 Feed rate (mm/min) 1,147 Feed per tooth 0.09 (mm/tooth) Z-axis depth of 5.0 Y-axis depth of cut (mm) 1.0 cut (mm)

[0073] The workpieces were subjected to side milling, and tool wear of the end mill was measured at three points on the clearance face after each 1-pass interval (10 m), with the maximum value recorded. The cutting operation was terminated when the clearance face wear of the end mill reached 0.2 mm or more, or when a total machining distance of 100 m (10 passes) was reached.

[0074] As can be seen in FIG. 6, the cutting fluids of Examples 1 and 2 exhibited a gradual increase in tool wear up to 10 passes (100 m) and maintained stable cutting performance. In Comparative Example 1, tool wear increased rapidly as the machining progressed, which is considered to result from the relatively rapid sedimentation of the hBN particles, such that from a cutting distance of 40 m, machining could not be performed smoothly with only cooling without lubrication. Comparative Examples 2 and 3 employed commercially available oil-based O/W emulsion type water-soluble cutting fluids. Although tool wear increased gradually up to 10 passes (100 m) and stable cutting performance was observed, tool wear was higher compared to Examples 1 and 2. Furthermore, in Comparative Examples 2 and 3, significant generation of oil vapor (smoke) occurred during the MQL machining process. Therefore, it was confirmed that the use of oil-based conventional cutting fluids in an MQL supply method poses substantial health risks.

[0075] Examples 1 and 2 demonstrate that, at a low concentration of 0.01 parts by weight of hexagonal boron nitride (hBN) particles relative to 100 parts by weight of water, the cutting performance is superior to that of conventional oil-based O/W emulsion-type water-soluble cutting fluids. This result evidences that the water-based cutting fluid of the present invention, which contains no oil and is based on hexagonal boron nitride (hBN), exhibits an excellent tool wear reduction effect. In other words, the water-based cutting fluid according to an embodiment of the present invention, comprising water, hexagonal boron nitride (hBN) particles, a dispersant, and a corrosion inhibitor, provides performance comparable to or superior to conventional oil-based O/W emulsion-type water-soluble cutting fluids, while also offering an environmental advantage in that no oil vapor (smoke) is generated due to oil combustion during metalworking.

[0076] FIG. 7 illustrates the measurement results of surface roughness obtained after completion of cutting operations in Examples 1 and 2 and Comparative Examples 1, 2, and 3. In both the horizontal and vertical directions relative to the end milling direction, the Examples exhibit relatively lower surface roughness compared to the Comparative Examples. This demonstrates the superior machining accuracy improvement effect of the oil-free hBN-based water-based cutting fluid according to an embodiment of the present invention, and confirms that, even at a low concentration of 0.01 parts by weight of hBN particles relative to 100 parts by weight of water, the cutting performance is superior to that of conventional oil-based O/W emulsion-type water-soluble cutting fluids. In summary, the oil-free water-based cutting fluid according to an embodiment of the present invention, which comprises water, hexagonal boron nitride (hBN) particles, a dispersant, and a corrosion inhibitor, provides machining performance (in terms of workpiece machining accuracy and tool wear resistance) comparable to or superior to conventional oil-based O/W emulsion-type water-soluble cutting fluids.

[0077] This demonstrates that the oil-free water-based cutting fluid according to one embodiment of the present invention is environmentally friendly due to the absence of oil components and is particularly suitable for application in minimum quantity lubrication (MQL) machining.

INDUSTRIAL APPLICABILITY

[0078] The oil-free water-based cutting fluid according to one embodiment of the present disclosure is not limited to applications in metalworking, but may also be applied to the machining of workpieces made of other materials such as plastics. In addition, due to the inherent excellent lubricating function, high thermal conductivity, and release properties of hexagonal boron nitride (hBN), the composition may also be used as a lubricant for various mechanical devices in which friction and wear occur.