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Applying Minimum Quantity Lubrication (MQL) Method on Milling of Martensitic Stainless Steel by Using Nano Mos2 Reinforced Vegetable Cutting Fluid
Available online at www.sciencedirect.com
ScienceDirect Procedia - Social and Behavioral Sciences 195 (2015) 2742 – 2747
World Conference on Technology, Innovation and Entrepreneurship
Applying Minimum Quantity Lubrication (MQL) Method on Milling of Martensitic Stainless Steel by Using Nano Mos2 Reinforced Vegetable Cutting Fluid Alper Uysala *, Furkan Demirena, Erhan Altana a
<ÕOGÕ]7HFKQLFDO8QLYHUVLW\'HSDUWPHQWRI0HFKDQLFDO(QJLQHHULQJ%HVLNWDV,VWDQEXO 7XUNH\
Abstract Martensitic stainless steel materials have provided some benefits for aerospace, automotive, hydroelectric engines, cutlery, defense, power hand tools, pump parts, valve seats, chisels, bushings, ball bearings, sporting equipment industry, dental and surgical instruments etc. due to their hardness, strength, and wear resistance. Machining operations such as milling, turning, drilling can be applied to give them the final form. But, these kinds of steels are specified as hard-to-machine materials owing to their high strength, low thermal conductivity and work hardening tendency during machining operations. However, martensitic stainless steels can be machined by using cutting fluids which are environmentally hazardous, unhealthy, and costly. In this study, minimum quantity lubrication (MQL) method was applied by using commercial vegetable cutting fluid and 1%wt. of nano MoS 2 (Molybdenum Disulphide) particles reinforced vegetable cutting fluid during milling of AISI 420 martensitic stainless steel with uncoated Tungsten Carbide (WC) cutting tool and the sustainable milling operation was performed. The experiments were carried out at constant cutting speed, feed, and depth of cut. Two different amounts of nanofluids – pressure air mist supplied by MQL system were applied as 20 ml/h and 40 ml/h. In the consequence of milling operations, initial tool wear and surface roughness were investigated. According to the experimental results, the MQL method reduced the tool wear and surface roughness. In addition, minimum tool wear and surface roughness values were obtained in nano MQL milling at 40 ml/h MQL flow rate. © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2015 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul University. Peer-review under responsibility of Istanbul Univeristy. Keywords: MQL; martensitic stainless steel; vegetable nanofluid; tool wear; surface roughness
* Corresponding author. Tel.: +90-212-383-2807; fax: +90-212-383-3024. E-mail address: [email protected]
1877-0428 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul Univeristy. doi:10.1016/j.sbspro.2015.06.384
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1. Introduction Stainless steel materials are used in many fields such as power plants, aerospace and automotive industries, dental and surgical instruments due to their hardness, high temperature properties, high creep rupture strength etc. However, they are generally known as difficult-to-machine materials because of the work-hardening tendency and low thermal conductivity. In literature, some researches have been carried out with regard to machining of these materials. Klim et al. (1996) developed a model considering crater and rake face wear as tool failure criteria to estimate the reliability of cutting tools under variable and constant feed conditions for 17-4PH stainless steel material. Lin (1998) investigated the reliability and failure of cutting tools in the face milling of stainless steel material. Chipping was accepted as tool life criterion and the effect of cutting parameters was examined. Selinder et al. (1998) evaluated the coated cemented carbide cutting tools in face milling experiments of austenitic stainless steel. In their study, the multilayered TiN/TaN (Titanium Nitride/Tantalum Nitride) and TiN/NbN (Titanium Nitride/Niobium Nitride) coated cemented carbide inserts were used. The coating was performed by PVD (Physical Vapor Deposition) technique. The results indicated that the multilayer coated cutting tools showed superior performance than single-layer coated cutting tools. Same result was reported in the study of Nordin et al. (2000). Sun et al. (1998) investigated the interface adhesion behavior between the cutting tool and austenitic stainless steel in milling operation. According to the experimental results, adhering phenomenon did not occur at high and low cutting speed, while it was formed at medium cutting speed. El-Hossein and Yahya (2005) performed an experimental study to investigate the performance of multilayered carbide inserts in end milling of AISI 304 austenitic stainless steels. Researchers examined the tool wear and the effects of cutting speed and feed rate on tool life. It was found that tool wear increased with increasing the cutting speed and decreasing the feed rate. Endrino et al. (2006) investigated the influence of the AlTiN (Aluminum Titanium Nitride) and AlCrN (Aluminum Chromium Nitride) coatings on wear mechanism and tool life during milling of AISI 316 austenitic stainless steel with carbide end mills. Minimal wear intensity was observed for cutting tools with the nano-crystalline AlTiN coating. Shao et al. (2007) studied the wear and failure mechanism of TiCN/TiN (Titanium Carbo-Nitride/Titanium Nitride) multilayer coated cemented carbide tool during milling process of 3%Co-12%Cr stainless steel. Researchers indicated that the abrasive wear and adhesion wear were observed in the initial and steady wear stages and diffusion happened in the final wear stage. Liew and Ding (2008) investigated the wear of uncoated and TiAlN (Titanium Aluminum Nitride) PVD coated carbide end mills in milling of modified AISI 420 martensitic stainless steel. Researchers presented that the coating prevented the chipping and enhanced the abrasive wear resistance of the cutting tool. Additionally, it was found that the failure of the cutting tool could be decreased by using cutting fluid. In the milling of stainless steels, developing coatings and applying cutting fluids have been studied to increase the cutting tool life, reduce the cutting tool failure, and to improve the surface finish quality. The developments in the coating technologies have succeeded these demands but the cutting tool costs have increased. In addition, the cutting fluids have been also useful but the usage of the cutting fluids has increased the production costs, adversely affected the health, and created biological and environmental problems. Therefore, MQL (Minimum Quantity Lubrication) method has been developed. In MQL machining, the coolant is supplied as a mixture of pressure air and cutting fluid in the form of an aerosol. Besides, EPA (Environmental Protection Agency) has imposed some sanctions on the applying ample amount of cutting fluid and the use of MQL method has become popular. Rahman et al. (2002) and Kishawy et al. (2005) compared the MQL method and flood cooling with each other. Researchers indicated that MQL method could be considered as an alternative to flood cooling because of the reduction in lubricant consumption. Additionally, de Lacalle et al. (2006) reported that the flood cooling was not effective in high speed milling due to unable to reach the inner zones of the tool teeth. But, the MQL flow penetrated in the cutting zone and acted in three different ways as cooling, lubricating, and removing the chips. Liao et al. (2007) performed a feasibility study on the MQL method in high speed end milling. The experiments were conducted under flood cooling and dry cutting conditions to compare the results of MQL method. Experimental results showed that the use of MQL method lead to the best performance and improved the surface finish. Besides, Fratila and Caizar (2011) presented that the MQL method could be successfully applied without affecting the machining process results such as surface roughness. Shahrom et al. (2013) investigated the MQL method and flood cooling in milling and
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determined the effect of lubrication conditions on the surface roughness. The MQL method gave better surface roughness than flood cooling. According to the performed studies, the MQL method can be an alternative to flood cooling in some milling operations, especially high speed milling. However, there is a need to develop its performance to machine hard-tocut materials such. For this reason, nanofluids have been produced by adding nanometer sized particles of metals, oxides, carbides, nitrides, or nanotubes such as carbon nanotube, TiO 2 (Titanium Dioxide), Al 2 O 3 (Aluminum Oxide), MoS 2 (Molybdenum Disulphide), and diamond to the cutting fluids. These nano additives can enhance the thermal conductivity and lubrication effect of the cutting fluids and improve the performance of MQL method. Shen et al. (2008a) investigated the performance of water based Al 2 O 3 and diamond nanofluids in MQL method. It was found that the nanofluids showed the benefits of reducing forces, improving surface roughness, and preventing workpiece burning. Shen et al. (2008b) evaluated the effect of nano MoS 2 particles based nanofluid in MQL method. The results showed that the MQL method with nanofluid application reduced the force and friction. Nam et al. (2011) studied the effect of nano diamond based nanofluid in the MQL method. The experimental results showed that the nanofluid MQL significantly increased tool life and reduced the torque and thrust force. Rahmati et al. (2014) investigated the surface quality and morphology of aluminum alloy in MQL milling with nano MoS 2 reinforced cutting fluid. Researchers presented that the MQL method with nano MoS 2 reinforced cutting fluid could be an alternative to obtain ideal surface quality. Previous studies presented that there was not much study about MQL milling of stainless steels, especially MQL with nanofluid. For this reason, we conducted MQL milling experiments of AISI 420 martensitic stainless steel by uncoated WC (Tungsten Carbide) cutting tool. It is known that the cutting tools wear relatively high in a short time at the beginning of the cutting operation and this rapid worn land affects the all process and reduces the tool life. For this reason, we investigated the effect of cutting condition on reducing the initial tool wear. In addition, the effect of cutting condition on the surface roughness was examined. In the MQL method, a commercial vegetable cutting fluid and a nanofluid were used. The nanofluid was prepared by adding nano MoS 2 particles to the vegetable cutting fluid at weight fraction of 1 to enhance its efficiency. Thus, sustainable and environmentally milling operation could be performed and hazardous and unhealthy effects of flood cooling could be also eliminated. 2. Experimental Study In experimental studies, slots were machined on AISI 420 martensitic stainless steel parts by First MCV-300 CNC milling machine. Chemical composition of the stainless steel parts is given in Table 1 and the steel parts were prepared in the dimensions of 400x250x4 mm. Table 1. Chemical composition of AISI 420 martensitic stainless steel. C%
Si%
Mn%
P%
S%
Cr%
0,36
0,42
0,37
0,022
0,003
13,11
In milling operations, SPHN120404 uncoated WC cutting tools were used and mounted on a 32 mm diameter end mill by mechanically. The milling experiments were conducted at constant spindle speed (995 rpm), feed rate (180 mm/min), and depth of cut (0,5 mm) under dry, MQL with vegetable cutting fluid, and MQL with nanofluid conditions. Table 2 shows the MQL conditions. Table 2. MQL conditions. Milling conditions
MQL flow rate
MQL pressure
Dry MQL with cutting fluid MQL with nanofluid
Nozzle angle
Nozzle distance
Nozzle tip diameter
50 mm
1 mm
10° 20 ml/h 40 ml/h
5 bar
(in parallel to the workpiece surface)
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(1% nano MoS 2 )
In MQL milling, Werte DKN 25 micro lubrication system was used and Eraoil KT/2000 commercial vegetable cutting fluid was chosen. Nano MoS 2 particles were added to the commercial vegetable cutting fluid at weight fraction of 1 to obtain the nanofluid. SEM (Scanning Electron Microscopy) image of nano MoS 2 particles can be seen in Fig. 1. To prepare the nanofluid, nano MoS 2 particles were dried in Termal G11420SD drying oven for 2 hours and then added to the cutting fluid. Additionally, lecitine was added as dispersant to obtain a homogeneous mixture. The mixture of nano MoS 2 particles and cutting fluid was blended by using Diahan WiseTis HG-15D digital homogenizer.
Fig. 1. SEM image of nano MoS 2 particles.
Surface roughness (R a ) measurements of milled slots were performed by using Time TR200 surface roughness tester. The cut-off length was adjusted as 0,8 mm and the resolution of tester is 0,001 ȝm. Five measurements were done on each surface and arithmetic means were calculated. The tool wears were observed by SOIF XJP-6A trinocular microscope and the tool wear measurements were performed by utilizing MShot digital imaging system. 3. Results and Discussion 3.1. The Effect of MQL Milling on Tool Wear At the beginning of the cutting operation, the cutting tools wear quickly and lose a significant part of their life. For this reason, it is important to reduce the initial tool wear. Fig. 2 shows the effect of cutting condition on the initial tool wear. Tool wear measurements were performed after milling for 40 seconds. The maximum tool wear was observed under dry milling. The MQL method decreased the tool wear due to the fact that the pulverized cutting fluid was able to reach the interface between the cutting tool and workpiece. Besides, the MQL flow rate had positive effect on the tool wear. Therefore, the tool wear decreased with increase of the pulverized cutting fluid amount. The tool wear reductions were calculated as 9,8% and 15,5% for the MQL flow rates of 20 ml/h and 40 ml/h, respectively when compared with the dry milling. In addition, the usage of nano MoS 2 particles reinforced cutting fluid in MQL method gave the minimum tool wear due to the lubrication effect of nano MoS 2 particles. The pulverized nanofluid reduced the friction between the cutting tool and workpiece and so less tool wears were observed. The nano MQL method could reduce the tool wear by 16,8% and 19,9% at 20 ml/h and 40 ml/h flow rates, respectively when compared with the dry milling. The minimum tool wear was obtained in milling with nano MoS 2 particles reinforced MQL method at 40 ml/h flow rate as seen in Fig. 2. 3.2. The Effect of MQL Milling on Surface Roughness The MQL method gave better surface roughness than dry milling and the minimum surface roughness was measured as 0,8644 ȝP in nano MQL milling at 40 ml/h flow rate (Fig. 3). The MQL method decreased the surface
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roughness by 8,8% and 22,5% for the flow rates of 20 ml/h and 40 ml/h, respectively when compared with the dry milling. In addition, the reductions of the surface roughness were determined as 36,3% and 39,2% at 20 ml/h and 40 ml/ flow rates in nano MQL milling, respectively as compared with the dry milling. According to Fig. 3, the difference between the surface roughness values measured at 20 ml/h and 40 ml/h flow rates was not too much for nanofluid because of the fact that the lubrication effect of nano MoS 2 particles had more effective than flow rate in terms of the surface roughness. However, this difference was much more for pure cutting fluid. Because more mixture of pressure air and cutting fluid reached to the cutting zone at 40 ml/h flow rate and this caused further reduction in surface roughness.
Fig. 2. Variation of initial tool wear with cutting condition (milling for 40 seconds).
Fig. 3. Variation of surface roughness with cutting condition.
4. Conclusion In this study, the effect of cutting conditions on the initial tool wear and surface roughness was investigated in milling of AISI 420 martensitic stainless steel. The experiments were conducted under dry, MQL with vegetable cutting fluid, and MQL with nanofluid. Nano MoS 2 particles were added to the vegetable cutting fluid at weight
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fraction of 1 to prepare the nanofluid. Experimental results showed that the MQL method could decrease the tool wear and surface roughness. Besides, an increment of the MQL flow rate caused a reduction in both the tool wear and surface roughness. Additionally, the use of nano MoS 2 particles reinforced cutting fluid in MQL milling gave the minimum tool wear and surface roughness due to the lubrication effect of nano MoS 2 particles. Acknowledgments This research has been supported by 7KH6FLHQWLILFDQG7HFKQRORJLFDO5HVHDUFK&RXQFLORI7XUNH\ 7h%ø7$. Project Number: 114M098. References de-Lacalle, L. N. L., Angulo, C., Lamikiz, A., & Sánchez, J. A. (2006). Experimental and numerical investigation of the effect of spray cutting fluids in high speed milling. Journal of Materials Processing Technology, 172, 11-15. El-Hossein, K. A. A., & Yahya, Z. (2005). High-speed end-milling of AISI 304 stainless steels using new geometrically developed carbide inserts. Journal of Materials Processing Technology, 162-163, 596-602. Endrino, J. L., Rabinovich, G. S. F., & Gey, C. (2006). Hard AlTiN, AlCrN PVD coatings for machining of austenitic stainless steel. Surface and Coatings Technology, 200, 6840-6845. Fratila, D., & Caizar, C. (2011). Application of Taguchi method to selection of optimal lubrication and cutting conditions in face milling of AlMg 3 . Journal of Cleaner Production, 19, 640-645. Kishawy, H. A., Dumitrescu, M., Ng, E. G., & Elbestawi, M. A. (2005). Effect of coolant strategy on tool performance, chip morphology and surface quality during high-speed machining of A356 aluminum alloy. International Journal of Machine Tools and Manufacture, 45, 219-227. Klim, Z., Ennajimi, E., Balazinski, M., & Fortin, C. (1996). Cutting tool reliability analysis for variable feed milling of 17-4PH stainless steel. Wear, 195, 206-213. Liao, Y. S., Lin, H. M., & Chen, Y. C. (2007). Feasibility study of the minimum quantity lubrication in high-speed end milling of NAK80 hardened steel by coated carbide tool. International Journal of Machine Tools and Manufacture, 47, 1667-1676. Liew, W. Y. H., & Ding, X. (2008). Wear progression of carbide tool in low-speed end milling of stainless steel. Wear, 265, 155-166. Lin, T. R. (1998). Reliability and failure of face-milling tools when cutting stainless steel. Journal of Materials Processing Technology, 79, 41-46. Nam, J. S., Lee, P. H., & Lee, S. W. (2011). Experimental characterization of micro-drilling process using nanofluid minimum quantity lubrication. International Journal of Machine Tools and Manufacture, 51, 649-652. Nordin, M., Sundström, R., Selinder, T. I., & Hogmark, S. (2000). Wear and failure mechanisms of multilayered PVD TiN/TaN coated tools when milling austenitic stainless steel. Surface and Coatings Technology, 133-134, 240-246. Rahman, M., Kumar, A. S., & Salam, M. U. (2002). Experimental evaluation on the effect of minimal quantities of lubricant in milling. International Journal of Machine Tools and Manufacture, 42, 539-547. Rahmati, B., Sarhan, A. A. D., & Sayuti, M. (2014). Morphology of surcae generated by end milling AL6061-T6 using molybdenum disulfide (MoS 2 ) nanolubrication in end milling machining. Journal of Cleaner Production, 66, 685-691. Selinder, T. I., Sjöstrand, M. E., Nordin, M., Larsson, M., Östlund, Å, & Hogmark, S. (1998). Performance of PVD TiN/TaN and TiN/NbN supperlattice coated cemented carbide tools in stainless steel machining. Surface and Coatings Technology, 105, 51-55. Shahrom, M. S., Yahya, N. M., & Yusoff, A. R. (2013). Taguchi method approach on effect of lubrication condition on surface roughness in milling operation. Procedia Engineering, 53, 594-599. Shao, H., Liu, L., & Qu, H. L. (2007). Machinability study on 3%Co-12%Cr stainless steel in milling. Wear, 263, 736-744. Shen, B., Shih, A. J., & Tung, S. C. (2008a). Application of nanofluids in minimum quantity lubrication grinding. Tribology Transactions, 51, 730-737. Shen, B., Malshe, A. P., Kalita, P., & Shih, A. J. (2008b). Performance of novel MoS 2 nanoparticles based grinding fluids in minimum quantity lubrication grinding. Transactions of NAMRI/SME, 36, 357-364. Sun, F., Li, Z., Jiang, D., & Chen, Bo. (1998). Adhering wear mechanism of cemented carbide cutter in the intervailic cutting of stainless steel. Wear, 214, 79-82.
ScienceDirect Procedia - Social and Behavioral Sciences 195 (2015) 2742 – 2747
World Conference on Technology, Innovation and Entrepreneurship
Applying Minimum Quantity Lubrication (MQL) Method on Milling of Martensitic Stainless Steel by Using Nano Mos2 Reinforced Vegetable Cutting Fluid Alper Uysala *, Furkan Demirena, Erhan Altana a
<ÕOGÕ]7HFKQLFDO8QLYHUVLW\'HSDUWPHQWRI0HFKDQLFDO(QJLQHHULQJ%HVLNWDV,VWDQEXO 7XUNH\
Abstract Martensitic stainless steel materials have provided some benefits for aerospace, automotive, hydroelectric engines, cutlery, defense, power hand tools, pump parts, valve seats, chisels, bushings, ball bearings, sporting equipment industry, dental and surgical instruments etc. due to their hardness, strength, and wear resistance. Machining operations such as milling, turning, drilling can be applied to give them the final form. But, these kinds of steels are specified as hard-to-machine materials owing to their high strength, low thermal conductivity and work hardening tendency during machining operations. However, martensitic stainless steels can be machined by using cutting fluids which are environmentally hazardous, unhealthy, and costly. In this study, minimum quantity lubrication (MQL) method was applied by using commercial vegetable cutting fluid and 1%wt. of nano MoS 2 (Molybdenum Disulphide) particles reinforced vegetable cutting fluid during milling of AISI 420 martensitic stainless steel with uncoated Tungsten Carbide (WC) cutting tool and the sustainable milling operation was performed. The experiments were carried out at constant cutting speed, feed, and depth of cut. Two different amounts of nanofluids – pressure air mist supplied by MQL system were applied as 20 ml/h and 40 ml/h. In the consequence of milling operations, initial tool wear and surface roughness were investigated. According to the experimental results, the MQL method reduced the tool wear and surface roughness. In addition, minimum tool wear and surface roughness values were obtained in nano MQL milling at 40 ml/h MQL flow rate. © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2015 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul University. Peer-review under responsibility of Istanbul Univeristy. Keywords: MQL; martensitic stainless steel; vegetable nanofluid; tool wear; surface roughness
* Corresponding author. Tel.: +90-212-383-2807; fax: +90-212-383-3024. E-mail address: [email protected]
1877-0428 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul Univeristy. doi:10.1016/j.sbspro.2015.06.384
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1. Introduction Stainless steel materials are used in many fields such as power plants, aerospace and automotive industries, dental and surgical instruments due to their hardness, high temperature properties, high creep rupture strength etc. However, they are generally known as difficult-to-machine materials because of the work-hardening tendency and low thermal conductivity. In literature, some researches have been carried out with regard to machining of these materials. Klim et al. (1996) developed a model considering crater and rake face wear as tool failure criteria to estimate the reliability of cutting tools under variable and constant feed conditions for 17-4PH stainless steel material. Lin (1998) investigated the reliability and failure of cutting tools in the face milling of stainless steel material. Chipping was accepted as tool life criterion and the effect of cutting parameters was examined. Selinder et al. (1998) evaluated the coated cemented carbide cutting tools in face milling experiments of austenitic stainless steel. In their study, the multilayered TiN/TaN (Titanium Nitride/Tantalum Nitride) and TiN/NbN (Titanium Nitride/Niobium Nitride) coated cemented carbide inserts were used. The coating was performed by PVD (Physical Vapor Deposition) technique. The results indicated that the multilayer coated cutting tools showed superior performance than single-layer coated cutting tools. Same result was reported in the study of Nordin et al. (2000). Sun et al. (1998) investigated the interface adhesion behavior between the cutting tool and austenitic stainless steel in milling operation. According to the experimental results, adhering phenomenon did not occur at high and low cutting speed, while it was formed at medium cutting speed. El-Hossein and Yahya (2005) performed an experimental study to investigate the performance of multilayered carbide inserts in end milling of AISI 304 austenitic stainless steels. Researchers examined the tool wear and the effects of cutting speed and feed rate on tool life. It was found that tool wear increased with increasing the cutting speed and decreasing the feed rate. Endrino et al. (2006) investigated the influence of the AlTiN (Aluminum Titanium Nitride) and AlCrN (Aluminum Chromium Nitride) coatings on wear mechanism and tool life during milling of AISI 316 austenitic stainless steel with carbide end mills. Minimal wear intensity was observed for cutting tools with the nano-crystalline AlTiN coating. Shao et al. (2007) studied the wear and failure mechanism of TiCN/TiN (Titanium Carbo-Nitride/Titanium Nitride) multilayer coated cemented carbide tool during milling process of 3%Co-12%Cr stainless steel. Researchers indicated that the abrasive wear and adhesion wear were observed in the initial and steady wear stages and diffusion happened in the final wear stage. Liew and Ding (2008) investigated the wear of uncoated and TiAlN (Titanium Aluminum Nitride) PVD coated carbide end mills in milling of modified AISI 420 martensitic stainless steel. Researchers presented that the coating prevented the chipping and enhanced the abrasive wear resistance of the cutting tool. Additionally, it was found that the failure of the cutting tool could be decreased by using cutting fluid. In the milling of stainless steels, developing coatings and applying cutting fluids have been studied to increase the cutting tool life, reduce the cutting tool failure, and to improve the surface finish quality. The developments in the coating technologies have succeeded these demands but the cutting tool costs have increased. In addition, the cutting fluids have been also useful but the usage of the cutting fluids has increased the production costs, adversely affected the health, and created biological and environmental problems. Therefore, MQL (Minimum Quantity Lubrication) method has been developed. In MQL machining, the coolant is supplied as a mixture of pressure air and cutting fluid in the form of an aerosol. Besides, EPA (Environmental Protection Agency) has imposed some sanctions on the applying ample amount of cutting fluid and the use of MQL method has become popular. Rahman et al. (2002) and Kishawy et al. (2005) compared the MQL method and flood cooling with each other. Researchers indicated that MQL method could be considered as an alternative to flood cooling because of the reduction in lubricant consumption. Additionally, de Lacalle et al. (2006) reported that the flood cooling was not effective in high speed milling due to unable to reach the inner zones of the tool teeth. But, the MQL flow penetrated in the cutting zone and acted in three different ways as cooling, lubricating, and removing the chips. Liao et al. (2007) performed a feasibility study on the MQL method in high speed end milling. The experiments were conducted under flood cooling and dry cutting conditions to compare the results of MQL method. Experimental results showed that the use of MQL method lead to the best performance and improved the surface finish. Besides, Fratila and Caizar (2011) presented that the MQL method could be successfully applied without affecting the machining process results such as surface roughness. Shahrom et al. (2013) investigated the MQL method and flood cooling in milling and
2744
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determined the effect of lubrication conditions on the surface roughness. The MQL method gave better surface roughness than flood cooling. According to the performed studies, the MQL method can be an alternative to flood cooling in some milling operations, especially high speed milling. However, there is a need to develop its performance to machine hard-tocut materials such. For this reason, nanofluids have been produced by adding nanometer sized particles of metals, oxides, carbides, nitrides, or nanotubes such as carbon nanotube, TiO 2 (Titanium Dioxide), Al 2 O 3 (Aluminum Oxide), MoS 2 (Molybdenum Disulphide), and diamond to the cutting fluids. These nano additives can enhance the thermal conductivity and lubrication effect of the cutting fluids and improve the performance of MQL method. Shen et al. (2008a) investigated the performance of water based Al 2 O 3 and diamond nanofluids in MQL method. It was found that the nanofluids showed the benefits of reducing forces, improving surface roughness, and preventing workpiece burning. Shen et al. (2008b) evaluated the effect of nano MoS 2 particles based nanofluid in MQL method. The results showed that the MQL method with nanofluid application reduced the force and friction. Nam et al. (2011) studied the effect of nano diamond based nanofluid in the MQL method. The experimental results showed that the nanofluid MQL significantly increased tool life and reduced the torque and thrust force. Rahmati et al. (2014) investigated the surface quality and morphology of aluminum alloy in MQL milling with nano MoS 2 reinforced cutting fluid. Researchers presented that the MQL method with nano MoS 2 reinforced cutting fluid could be an alternative to obtain ideal surface quality. Previous studies presented that there was not much study about MQL milling of stainless steels, especially MQL with nanofluid. For this reason, we conducted MQL milling experiments of AISI 420 martensitic stainless steel by uncoated WC (Tungsten Carbide) cutting tool. It is known that the cutting tools wear relatively high in a short time at the beginning of the cutting operation and this rapid worn land affects the all process and reduces the tool life. For this reason, we investigated the effect of cutting condition on reducing the initial tool wear. In addition, the effect of cutting condition on the surface roughness was examined. In the MQL method, a commercial vegetable cutting fluid and a nanofluid were used. The nanofluid was prepared by adding nano MoS 2 particles to the vegetable cutting fluid at weight fraction of 1 to enhance its efficiency. Thus, sustainable and environmentally milling operation could be performed and hazardous and unhealthy effects of flood cooling could be also eliminated. 2. Experimental Study In experimental studies, slots were machined on AISI 420 martensitic stainless steel parts by First MCV-300 CNC milling machine. Chemical composition of the stainless steel parts is given in Table 1 and the steel parts were prepared in the dimensions of 400x250x4 mm. Table 1. Chemical composition of AISI 420 martensitic stainless steel. C%
Si%
Mn%
P%
S%
Cr%
0,36
0,42
0,37
0,022
0,003
13,11
In milling operations, SPHN120404 uncoated WC cutting tools were used and mounted on a 32 mm diameter end mill by mechanically. The milling experiments were conducted at constant spindle speed (995 rpm), feed rate (180 mm/min), and depth of cut (0,5 mm) under dry, MQL with vegetable cutting fluid, and MQL with nanofluid conditions. Table 2 shows the MQL conditions. Table 2. MQL conditions. Milling conditions
MQL flow rate
MQL pressure
Dry MQL with cutting fluid MQL with nanofluid
Nozzle angle
Nozzle distance
Nozzle tip diameter
50 mm
1 mm
10° 20 ml/h 40 ml/h
5 bar
(in parallel to the workpiece surface)
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(1% nano MoS 2 )
In MQL milling, Werte DKN 25 micro lubrication system was used and Eraoil KT/2000 commercial vegetable cutting fluid was chosen. Nano MoS 2 particles were added to the commercial vegetable cutting fluid at weight fraction of 1 to obtain the nanofluid. SEM (Scanning Electron Microscopy) image of nano MoS 2 particles can be seen in Fig. 1. To prepare the nanofluid, nano MoS 2 particles were dried in Termal G11420SD drying oven for 2 hours and then added to the cutting fluid. Additionally, lecitine was added as dispersant to obtain a homogeneous mixture. The mixture of nano MoS 2 particles and cutting fluid was blended by using Diahan WiseTis HG-15D digital homogenizer.
Fig. 1. SEM image of nano MoS 2 particles.
Surface roughness (R a ) measurements of milled slots were performed by using Time TR200 surface roughness tester. The cut-off length was adjusted as 0,8 mm and the resolution of tester is 0,001 ȝm. Five measurements were done on each surface and arithmetic means were calculated. The tool wears were observed by SOIF XJP-6A trinocular microscope and the tool wear measurements were performed by utilizing MShot digital imaging system. 3. Results and Discussion 3.1. The Effect of MQL Milling on Tool Wear At the beginning of the cutting operation, the cutting tools wear quickly and lose a significant part of their life. For this reason, it is important to reduce the initial tool wear. Fig. 2 shows the effect of cutting condition on the initial tool wear. Tool wear measurements were performed after milling for 40 seconds. The maximum tool wear was observed under dry milling. The MQL method decreased the tool wear due to the fact that the pulverized cutting fluid was able to reach the interface between the cutting tool and workpiece. Besides, the MQL flow rate had positive effect on the tool wear. Therefore, the tool wear decreased with increase of the pulverized cutting fluid amount. The tool wear reductions were calculated as 9,8% and 15,5% for the MQL flow rates of 20 ml/h and 40 ml/h, respectively when compared with the dry milling. In addition, the usage of nano MoS 2 particles reinforced cutting fluid in MQL method gave the minimum tool wear due to the lubrication effect of nano MoS 2 particles. The pulverized nanofluid reduced the friction between the cutting tool and workpiece and so less tool wears were observed. The nano MQL method could reduce the tool wear by 16,8% and 19,9% at 20 ml/h and 40 ml/h flow rates, respectively when compared with the dry milling. The minimum tool wear was obtained in milling with nano MoS 2 particles reinforced MQL method at 40 ml/h flow rate as seen in Fig. 2. 3.2. The Effect of MQL Milling on Surface Roughness The MQL method gave better surface roughness than dry milling and the minimum surface roughness was measured as 0,8644 ȝP in nano MQL milling at 40 ml/h flow rate (Fig. 3). The MQL method decreased the surface
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roughness by 8,8% and 22,5% for the flow rates of 20 ml/h and 40 ml/h, respectively when compared with the dry milling. In addition, the reductions of the surface roughness were determined as 36,3% and 39,2% at 20 ml/h and 40 ml/ flow rates in nano MQL milling, respectively as compared with the dry milling. According to Fig. 3, the difference between the surface roughness values measured at 20 ml/h and 40 ml/h flow rates was not too much for nanofluid because of the fact that the lubrication effect of nano MoS 2 particles had more effective than flow rate in terms of the surface roughness. However, this difference was much more for pure cutting fluid. Because more mixture of pressure air and cutting fluid reached to the cutting zone at 40 ml/h flow rate and this caused further reduction in surface roughness.
Fig. 2. Variation of initial tool wear with cutting condition (milling for 40 seconds).
Fig. 3. Variation of surface roughness with cutting condition.
4. Conclusion In this study, the effect of cutting conditions on the initial tool wear and surface roughness was investigated in milling of AISI 420 martensitic stainless steel. The experiments were conducted under dry, MQL with vegetable cutting fluid, and MQL with nanofluid. Nano MoS 2 particles were added to the vegetable cutting fluid at weight
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fraction of 1 to prepare the nanofluid. Experimental results showed that the MQL method could decrease the tool wear and surface roughness. Besides, an increment of the MQL flow rate caused a reduction in both the tool wear and surface roughness. Additionally, the use of nano MoS 2 particles reinforced cutting fluid in MQL milling gave the minimum tool wear and surface roughness due to the lubrication effect of nano MoS 2 particles. Acknowledgments This research has been supported by 7KH6FLHQWLILFDQG7HFKQRORJLFDO5HVHDUFK&RXQFLORI7XUNH\ 7h%ø7$. Project Number: 114M098. References de-Lacalle, L. N. L., Angulo, C., Lamikiz, A., & Sánchez, J. A. (2006). Experimental and numerical investigation of the effect of spray cutting fluids in high speed milling. Journal of Materials Processing Technology, 172, 11-15. El-Hossein, K. A. A., & Yahya, Z. (2005). High-speed end-milling of AISI 304 stainless steels using new geometrically developed carbide inserts. Journal of Materials Processing Technology, 162-163, 596-602. Endrino, J. L., Rabinovich, G. S. F., & Gey, C. (2006). Hard AlTiN, AlCrN PVD coatings for machining of austenitic stainless steel. Surface and Coatings Technology, 200, 6840-6845. Fratila, D., & Caizar, C. (2011). Application of Taguchi method to selection of optimal lubrication and cutting conditions in face milling of AlMg 3 . Journal of Cleaner Production, 19, 640-645. Kishawy, H. A., Dumitrescu, M., Ng, E. G., & Elbestawi, M. A. (2005). Effect of coolant strategy on tool performance, chip morphology and surface quality during high-speed machining of A356 aluminum alloy. International Journal of Machine Tools and Manufacture, 45, 219-227. Klim, Z., Ennajimi, E., Balazinski, M., & Fortin, C. (1996). Cutting tool reliability analysis for variable feed milling of 17-4PH stainless steel. Wear, 195, 206-213. Liao, Y. S., Lin, H. M., & Chen, Y. C. (2007). Feasibility study of the minimum quantity lubrication in high-speed end milling of NAK80 hardened steel by coated carbide tool. International Journal of Machine Tools and Manufacture, 47, 1667-1676. Liew, W. Y. H., & Ding, X. (2008). Wear progression of carbide tool in low-speed end milling of stainless steel. Wear, 265, 155-166. Lin, T. R. (1998). Reliability and failure of face-milling tools when cutting stainless steel. Journal of Materials Processing Technology, 79, 41-46. Nam, J. S., Lee, P. H., & Lee, S. W. (2011). Experimental characterization of micro-drilling process using nanofluid minimum quantity lubrication. International Journal of Machine Tools and Manufacture, 51, 649-652. Nordin, M., Sundström, R., Selinder, T. I., & Hogmark, S. (2000). Wear and failure mechanisms of multilayered PVD TiN/TaN coated tools when milling austenitic stainless steel. Surface and Coatings Technology, 133-134, 240-246. Rahman, M., Kumar, A. S., & Salam, M. U. (2002). Experimental evaluation on the effect of minimal quantities of lubricant in milling. International Journal of Machine Tools and Manufacture, 42, 539-547. Rahmati, B., Sarhan, A. A. D., & Sayuti, M. (2014). Morphology of surcae generated by end milling AL6061-T6 using molybdenum disulfide (MoS 2 ) nanolubrication in end milling machining. Journal of Cleaner Production, 66, 685-691. Selinder, T. I., Sjöstrand, M. E., Nordin, M., Larsson, M., Östlund, Å, & Hogmark, S. (1998). Performance of PVD TiN/TaN and TiN/NbN supperlattice coated cemented carbide tools in stainless steel machining. Surface and Coatings Technology, 105, 51-55. Shahrom, M. S., Yahya, N. M., & Yusoff, A. R. (2013). Taguchi method approach on effect of lubrication condition on surface roughness in milling operation. Procedia Engineering, 53, 594-599. Shao, H., Liu, L., & Qu, H. L. (2007). Machinability study on 3%Co-12%Cr stainless steel in milling. Wear, 263, 736-744. Shen, B., Shih, A. J., & Tung, S. C. (2008a). Application of nanofluids in minimum quantity lubrication grinding. Tribology Transactions, 51, 730-737. Shen, B., Malshe, A. P., Kalita, P., & Shih, A. J. (2008b). Performance of novel MoS 2 nanoparticles based grinding fluids in minimum quantity lubrication grinding. Transactions of NAMRI/SME, 36, 357-364. Sun, F., Li, Z., Jiang, D., & Chen, Bo. (1998). Adhering wear mechanism of cemented carbide cutter in the intervailic cutting of stainless steel. Wear, 214, 79-82.