Study on High-Speed Machining of 2219 Aluminum Utilizing Nanoparticle-Enhanced Minimum Quantity Lubrication (MQL) Technique

doi:10.21203/rs.3.rs-1868808/v1

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Study on High-Speed Machining of 2219 Aluminum Utilizing Nanoparticle-Enhanced Minimum Quantity Lubrication (MQL) Technique

https://doi.org/10.21203/rs.3.rs-1868808/v1

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The lubricant choice is a critical factor in the high-speed machining process, and it can impact the machining surface quality and also the ultimate material properties. This paper investigates the microstructural surface finishing and heat generated during the high-speed cutting process (machining speed 3800 RPM) of 2219 aluminum alloy. The study examines flood coolant and five different nanofluids made by synthesizing 0.2–2% concentration of Al₂O₃ nanoparticles into ultra-food-grade mineral oil utilizing nanoparticle-enhanced minimum quantity lubrication (MQL) technique. In the MQL method, unlike the current known cooling fluid systems, the nanofluid provides a thin lubricant film that leads the heat created by friction to be transmitted to the chips and exits the interface. Also, the small amount of lubricant used for MQL makes this technique more environmentally friendly. The study revealed the chemistry between the MQL of choice and the corresponding surface finishing. As a result, the nanofluid with a 0.5% concentration of nanoparticles has the most optimal machining result. Furthermore, increasing nanoparticle concentration does not indicate any further improvement in the result. The results of this study could be instrumental to developing environmental-friendly machining solutions for aluminum alloys at commercial scales.

Aluminum Alloy

Minimum Quantity Lubrication (MQL)

Nanofluids

When high-temperature applications are needed, 2219 Aluminum Alloy is the most popular alloy to be used [1]. The high strength, low ductility, good machinability, lightweight, and excellent fracture toughness [2], are the characteristics that make this alloy to be chosen in Liquid Oxygen (LOX) feedline launch vehicle systems by most known aerospace and space transportation companies such as SpaceX, ULA (United Launch Alliance), and the Boeing.

While this alloy offers superior benefits to be used in space applications, the previous studies indicate surface finish is severely scratched and becomes rougher with the increase in total cutting depth [3]. Also, models that are not fully acceptable were developed by several regression analysis on the surface roughness measurements.[4]. This improper surface roughness challenge generally can be resolved by additional sanding, polishing, and chemical etching processes to obtain a smooth surface finish. However, this is a fact that chips are torn rather than sheared from the workpiece during cutting processes [5]. Therefore, one of the key aspects to achieve proper surface finishing while avoiding the above additional non-value-added operations is the utilization of appropriate coolants and cutting fluids to transport chips, waste, and removed workpiece material.

Flooding the workpiece and tooling with cooling fluid, mostly coolant mix with water is a common cooling method in conventional machining [6]. Using flood coolant in conventional machining is harmful to environment and impact the health of operators, technicians, and other personnel. [7]. Transportation, maintenance, appropriate disposal, storage and real estate costs are some major factors in conventional forms of cooling which create significant negative impact on manufacturing businesses. [8]. The other downside of using coolant is thermal shock. During the cutting process friction generates between the workpiece and cutting tool raise the temperature in the cutting area and make the workpiece material extremely hot. Meanwhile, coolant is poured on the surface and instantly cool it down. Then the workpiece is immediately returned to the cutting operation and heats up again. This constant back and forth heats up and cool down leads to thermal shock in the material [9].

The dry machining process can solve this issue to some extent. This method utilizes no lubrication to machine parts [10]. However, dry machining can negatively affect machining characteristics and material properties such as precision, and material failure becomes a concern for the operator when machining dry [11].

Minimum quantity lubrication (MQL), which is also known as “Near-dry machining” or “NDM” and “Micro lubrication” or “Micro-lubrification,” is a firm method in machining processes which was able to resolve the issue with disposal and/or recycling of the used cutting fluid. [12]. The concept of MQL is fundamentally different than traditional flood coolants. After the high-pressure gas is mixed with a small amount of cutting fluid, microdroplets are formed and sprayed into the machining area. The high-pressure airflow plays the role of cooling and chips removal [13]. The lubricant fluid cohere on the machined surface of the workpiece, becomes a protective film and acting as a lubricant [14]. The MQL concept was invented years ago to address the concern with environmental and occupational hazards impact cause by fluid particles. By reducing consumption of the cutting fluid, lubricant costs decline and leads to economic benefits along with reducing the cleaning time [15].

In MQL technique, minimum amount of oil mixed with nanoparticle and compress air and then sprays onto the surface of the workpiece[16]. An element of a matter that is between 1 to 100 nanometers (nm) in diameter is denominated as a nanoparticle or ultrafine particle. The nanoparticle can provide different physical and chemical properties than their bigger size. It means material properties will be changed once they become smaller and smaller until they get close to their atomic size. Although MQL choice depends on numerous characteristics such as workpiece material, hardness, restraint stress, and required cooling ratio, the previous research indicate that nanoparticles have a superior scatter property and transfer heat better between surfaces and sub-surfaces [17].

Gharaibeh N. used three cutting fluids: mineral used oil, kerosene, and natural used oil (refined sunflower oil) to study their effect on the surface roughness as cutting fluids compared to a common lubricating oil used in the cooling process. Result shows the best roughness coefficient provided by mineral used oil [15]. Singh and Kumar performed an experimental investigation of vegetable & mineral oil performance during machining of EN31 alloy steel with minimum quantity lubrication. Machining of EN31 steel alloy using both mineral oil and vegetable oil utilizing MQL technique revealed that the surface roughness of vegetable oil and mineral oil are almost comparable and very close [16]. Bahari et al. studied the friction and wear response of vegetable oils and mineral engine oil in a reciprocating sliding contact at severe contact conditions. The study concluded the mineral engine oil was far superior in wear resistance over vegetable oils [18]. Hadi et al. presents an investigation into Minimum Quantity Lubrication with Gamma- Al₂O₃ Nanoparticles in end milling processes of AISI D3 steel work material to analyze the effects of cutting parameters on surface roughness. It was revealed that surface roughness improved about 15% in comparison to pure MQL [19]. The excessive temperature can negatively impact the material properties, tool life and increase tool wear progression. Salur et al. evaluated tool wear, cutting temperature, and power consumption during end milling of AISI 1040 Steel while MQL and dry environments were used. Through this research it was found out that tool wear, cutting temperature, and power consumption was significantly improved in MQL technique in comparison with dry milling.[17].

Dongkun et al. analyzed different volume concentrations of Molybdenum Disulfide (MoS₂) nanoparticles in their experiments on MQL lubrication and studied their pertinent surface roughness. They studied 1%, 2%, and 3% MoS₂ concentrations during the grinding process and the result exposed. By increasing the MoS2 nanoparticle concentration the surface roughness on the workpiece initially increased but after a certain point of nanoparticle concentration, the surface quality decreases. The optimum surface roughness was observed when 2% MoS2 nanoparticle concentration was used.[20]. Therefore, the fluid type, nanoparticles, and their concentration have a strong effect on cutting performance.

Molaie et al. have shown that MQL with water-based nanofluids can provide a key value-added quality to ultrasonic vibration-assisted surface grinding. The research also emphasizes the type and concentration of nanoparticles in the base fluid and the shape of the nanoparticles and their molecular structures are critical factors impacting the result in the nano lubricant grinding process utilizing ultrasonic vibration [21]. According to Duc et al., in their research about Micro/Nanofluids in Sustainable Machining, the performance of nanofluids is better than micro fluids in reducing cutting temperatures, cutting forces, tool flank wear, and surface roughness of the machined surface [22].

Based on the literature study, it has been proven when nanoparticles are used as additives to the lubricants, various properties such as surface finish roughness, thermal stability, anti-friction, anti-wear, and extreme pressure can be improved while providing a high reaction rate with the surface. However, to the best of our knowledge, there have been no comprehensive studies done towards understanding the effects of nanoparticle enhance MQL on Al2219 alloy.

This research investigates the effects of critical process parameters on the surface finishing and produced heat using nanoparticle-enhanced minimum quantity lubrication (MQL) instead of conventional cooling and/or dry machining for cutting 2219 Aluminum Alloy. The study aims to understand the chemistry between the MQL of choice and the corresponding surface roughness.

The nanoparticle lubricant developed for this research is a mixture of nanopowder aluminum oxide (Al₂O₃, gamma) with ultra-pro-food-grade mineral oil. The nanopowder aluminum oxide (Al₂O₃, gamma) is mixed with ultra-pro-food-grade mineral oil for a minimum of six hours using an electric laboratory centrifuge. Typically, lubricant flow rate of 50 to 500 ml/h is misting or atomizing on the cutting zone in MQL technique to minimize the quantity of lubricant [12]. In this experiment, an aerosol atomizer system was utilized to apply a minimum amount of developed lubricant on the cutting surface. The aluminum specimens were cut by a high-speed saw cutting machine using the following two lubricants: #1 Conventional cutting (Coolant) #2 Indigenously-developed MQL lubricant with different concentrations of the nanoparticle. Then the cut samples were studied for comparison of microstructural surface finish and heat temperature during the process.

2.1. Materials Used

In the present investigation, the high-strength aluminum alloy 2219-T8 material was used. To achieve this temper (T8), the metal is solution heat-treated, strain hardened, then artificially aged at 325°F for 18 hours, and then air cool. The size of the specimen is 6 X 6 (L × W) inches with 0.250 inches in thickness. The material chemical composition and mechanical properties are referenced in Tables 1 and 2.

Table 1

Material Chemical Composition
Al	Mn	Mg	V	Si	Cr	Ni	Ti	Cu	Zr	Fe	Zn
92.3	0.31	0.01	0.088	0.06	0.003	0.00	0.062	6.35	0.12	0.12	0.02

Table 2

Material Mechanical properties
Yield Str. (Ksi)*	Ultimate. Str. (Ksi)	% Elongation	Hardness (HRBW)	% Conductivity (IACS)**
53.8	68.0	9.5	74–76	35.5–36.0
* Modulus of Elasticity (Yield Strength)
** IACS (International Annealed Copper Standard)

2.2. Experimental Setup

All steps of this experimental assays are performed at room temperature (68 to 77°F). Circular High-Speed Saw Cut (15-Amp, 14-Inch, 3800 RPM) with a 1.8 KW motor was used with conventional high-speed aluminum oxide, Type 1, Metal Cutting Blade to cut Aluminum 2219-T8 specimens with 0.250 inches thickness. The cooling fluid was supplied as a mixture of mineral oil and nanoparticle and delivered onto the surface of the workpiece undergoing the cutting and saw blade utilizing an aerosol atomizer mechanism (Fig. 1). The summary of the equipment/instrumentation used in this study is shown in Table 3.

Table 3

Technical Instruments in this study
Tool Name	Manufacturer	Model	Major Specifications
Circular High-Speed Saw Cut	PORTER-CABLE	PCE700	Speed: 3800 RPM Power: 1.8 KW Size: 14-Inch
Saw Wheel/Blade	PORTER-CABLE	‎A24-R	Size: 14" x 3/32" x 1” Max RPM: 4300
*Laser Thermometer	Extech	42510A	Temperature Range: -58 to 1200°F Resolution: 0.1°F degree
*Profilometer/ Surface Roughness Tester	Mitutoyo	SJ-310	Resolution: 0.002 µm (0.078 µin)
Automatic Electric Mist Spray	Reditbone	E-01	Bottle size: 350 ml Flow Rate Range: 4200 − 460 ml/hr
Electric Lab Centrifuge	DOC.ROYAL	GH-44	Speed: 0-4000 RPM Timer Range: 0–60 min or always on Power: 25 W
*Digital Scale	Fuzion	PT500	Weighing Range: 0.03–500 grams Resolution: 0.01 gram
* Equipment is calibrated to NIST and ISO 17025 standards

2.3. MQL Dispersion Preparation

The MQL choice is ultra-pro-food-grade mineral oil as the base oil mixed with different concentrations of Aluminum Oxide (Al₂O₃) nanoparticles. The oil mixture is enhanced using the following five different nanoparticle concentrations:

Pure Mineral Oil
0.2% Al₂O₃ nanoparticles
0.5% Al₂O₃ nanoparticles
1% Al₂O₃ nanoparticles
2% Al₂O₃ nanoparticles

The Aluminum Oxide nanoparticle (Al₂O₃, gamma) properties that were used for this study are described in Table 4.

Table 4

Aluminum Oxide nanoparticle (Al₂O₃, gamma) properties
Material	Brand	Color	Chemical Composition							Particle Size	Purity
Nano Alumina	XFNANO	White	Al2O3	Ca	Fe	K	Na	Mn	Si	10–15 nm	99.9%
Nano Alumina	XFNANO	White	99.99%	\(\le\)1 ppm	\(\le\)18 ppm	\(\le 29\) ppm	\(\le 35\) ppm	\(\le\)1.2 ppm	\(\le\)16 ppm	10–15 nm	99.9%

In this experiment, initially, MicroSol, 585XT Coolant (Table 5), and then pure Mineral Oil (mixed with 0% nanoparticle) were used in the form of flood-cutting fluid onto the surface of the aluminum workpiece and saw blade undergoing the cutting process.

Furthermore, Electric Lab Centrifuge was utilized with 4000 RPM for a minimum of six hours to synthesize aluminum oxide nanoparticles with mineral oil to achieve the desired concentrations. The prepared nanofluid was sprayed in the form of MQL onto the surface of the workpiece during the cutting process. Samples were cut using the six cutting lubricants mentioned in Table 6 to evaluate surface finish roughness and heat temperature immediately after the cutting process.

Table 5

MicroSol, 585XT Physical Properties
Color (Concentrate)	Straw
Odour (Concentrate)	Mild amine
Form (Concentrate)	Liquid
Flash Point (Concentrate)	> 160°C (320°F)
pH (Concentrate as Range)	9.2–10.2
pH (Typical Operating as Range)	8.8–9.8
Coolant Refractometer Factor	1.2

Table 6

Lubricant types used in this study
Lubricant 1	Flood Coolant	Lubricant 4	0.5% Al₂O₃ nanoparticles
Lubricant 2	Pure Mineral Oil	Lubricant 5	1% Al₂O₃ nanoparticles
Lubricant 3	0.2% Al₂O₃ nanoparticles	Lubricant 6	2% Al₂O₃ nanoparticles

For each lubricant mixture, the experiments were repeated five times to ensure the accuracy of collected data. The workpiece temperatures were 65°F immediately before the cutting process.

3.1. Surface roughness and surface micromorphology

Surface finish plays an essential role in product quality and manufacturing process planning. The surface finish of the workpiece can be quantitatively determined through surface roughness measurements. Figure 3 and Fig. 4 show the surface roughness and surface micromorphology of the workpieces cut using six different lubricant mixtures. The surface roughness was measured using a profilometer (Make: Mitutoyo, Model: SJ-310).

The figures indicate that the 0.5% Al2O3 nanofluid produces the best surface finish among the various MQL combinations (63% improvement over pure MQL). The result of 0.5% MQL is almost comparable (within 10%) to the surface finish obtained during the flood coolant machining. Flood coolant has the obvious advantage of frequent removal of the machining debris from the machining zone resulting in a smoother surface. Within the MQL conditions, the application of nanofluid improves the surface finish as the nanoparticles result in rolling friction as opposed to sliding friction (in the case of pure MQL). It is seen that the tribological properties were improved with an increase in the concentration of nanoparticles. However, as the concentration of MQL is increased beyond 0.5%, the resulting surface shows higher surface roughness values. This can be explained by the fact that beyond a specific concentration (0.5% in this case), the nanoparticles tend to precipitate on the workpiece surface and penetrate into the machined regions, micro grooves, slits, as well as into chips. This prevents MQL fluid from reaching the machined cavities because of increased viscosity, thereby resulting in inadequate lubrication and higher surface roughness.

3.2. Temperature generated during high-speed saw cutting

The heat generated on the workpiece and cutting tooltip is vital for the tool's performance and the quality of the finished product. The effect of the cutting temperature, mainly when it is high, is most detrimental to both the tool and workpiece. The temperature of the cutting zone immediately after the machining under different lubricant types was measured using a laser thermometer and is shown in Fig. 5. According to this graph, the best cooling happened during the flood coolant condition because of the presence of vast quantities of coolant used. Also, less heat was generated when nanoparticle fluid was used in comparison to pure mineral oil MQL. This also is the result of the fact that the rolling friction generates less amount of heat compared to sliding friction. When more than 0.5% nanoparticle concentration was used, possibly the Al₂O₃ particles get clogged on the surface and change the format of the friction from rolling to sliding. Sliding friction creates more heat and a rougher surface. The temperature gradually drops when Al₂O₃ concentration is increased. Yet, by increasing the concentration by more than 0.5%, the magnitude of the heat temperature rises again. Among all the concentrations of nanoparticle-enhanced lubricants considered, 0.5% shows the best result, and the highest heat generated was when pure mineral oil was applied in MQL form.

The present study investigated the nanoparticle-enhanced MQL-based high-speed cutting of Aluminum Alloy 2219. Nanofluids with different concentrations of nanoparticles are compared along with pure MQL and flood coolant conditions. The following key conclusions are drawn from this study:

The increase in nanoparticle concentration helps improve the surface finish under MQL machining. However, after a certain point of nanoparticle concentration, the surface quality decreases.
There is very little difference in surface roughness obtained using conventional flood coolant and MQL using 0.5% nanoparticle concentration.
Compared to pure MQL, 0.5% nanoparticle concentration MQL showed 63% improvement in surface finish.
The temperature analysis of the cutting zone immediately after the machining showed that 0.5% nanoparticle concentration resulted in the lowest cutting temperature.
Further investigations are needed to understand the impact of the nanoparticle concentrations on the tool wear, tool life, and the MQL-based machining economics.

a. Funding

The College of Engineering and Computer Science (ECS) facilities at California State University Fullerton are acknowledged.

b. Conflicts of interest/Competing interests

The authors have no conflicts of interest to declare. All co-authors have seen and agree with the manuscript's contents, and there is no financial interest to report. We certify that the submission is original work and is not under review at any other publication.

c. Availability of data and material

Not applicable

d. Code availability

Not applicable

e. Ethics approval

Not applicable

f. Consent to participate

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g. Consent for publication

Not applicable

h. Authors' contributions

Dr. Sagil James conceived the idea for research. Dr. James and Mehrshad Mazaheri designed the methodology and experimental setup and outlined the paper. Mehrshad conducted the literature review, performed experiments, and collected data. Dr. James and Mehrshad analyzed the data and wrote the manuscript's results.

Mondol, S., et al., Improvement of high temperature strength of 2219 alloy by Sc and Zr addition through a novel three-stage heat treatment route. Materials Science and Engineering: A, 2018. 732: p. 157-166.
Sivaprasad, K., et al., Achieving Superior Strength and Ductility Combination Through Cryorolling in 2219 Aluminum Alloy. Journal of Materials Engineering and Performance, 2020. 29(10): p. 6809-6817.
Gatto, A., E. Bassoli, and L. Iuliano, Performance Optimization in Machining of Aluminium Alloys for Moulds Production: HSM and EDM. Aluminium Alloys, Theory and Applications, 2011: p. 355-376.
MuellerHummel, P., Process understanding of dry drilling CFRP/aluminium and AL/AL stacks in IT8 quality. SAE International Journal of Aerospace, 2016. 9(2): p. 217.
Jawahir, I.S. and C.A. Van Luttervelt, Recent developments in chip control research and applications. CIRP annals, 1993. 42(2): p. 659-693.
Park, K.-H., et al., A study on droplets and their distribution for minimum quantity lubrication (MQL). International Journal of Machine Tools and Manufacture, 2010. 50(9): p. 824-833.
James, S. and S.M. Nejadian, Experimental study on high-speed saw cutting of hybrid composite stacks using nanoparticle-enhanced minimum quantity lubrication. The International Journal of Advanced Manufacturing Technology, 2020. 110(11): p. 3077-3090.
Le Coz, G. and D. Dudzinski, Temperature variation in the workpiece and in the cutting tool when dry milling Inconel 718. The International Journal of Advanced Manufacturing Technology, 2014. 74(5-8): p. 1133-1139.
Meshreki, M., et al. Investigation of drilling of CFRP-aluminum stacks under different cooling modes. American Society of Mechanical Engineers.
Sreejith, P.S., Machining of 6061 aluminium alloy with MQL, dry and flooded lubricant conditions. Materials letters, 2008. 62(2): p. 276-278.
Zhang, Y., et al., Modeling and Simulation of Nanofluid Minimum Quantity Lubrication Surface Grinding Thermal Stress. The Open Mechanical Engineering Journal, 2015. 9(1).
Boubekri, N., V. Shaikh, and P.R. Foster, A technology enabler for green machining: minimum quantity lubrication (MQL). Journal of Manufacturing Technology Management, 2010.
Brinksmeier, E. and R. Janssen, Drilling of multi-layer composite materials consisting of carbon fiber reinforced plastics (CFRP), titanium and aluminum alloys. CIRP Annals, 2002. 51(1): p. 87-90.
Khan, I., K. Saeed, and I. Khan, Nanoparticles: Properties, applications and toxicities. Arabian journal of chemistry, 2019. 12(7): p. 908-931.
Gharaibeh, N., Vegetable and mineral used oils as cutting fluids: effect on surface roughness of aluminum alloy. Journal of Surface Engineered Materials and Advanced Technology, 2016. 6(4): p. 176-182.
Singh, G., et al., Experimental investigations of vegetable & mineral oil performance during machining of EN-31 steel with minimum quantity lubrication. Int. J. Res. Eng. Technol., 2013. 2(6): p. 1030-1037.
Salur, E., et al., The Effects of MQL and Dry Environments on Tool Wear, Cutting Temperature, and Power Consumption during End Milling of AISI 1040 Steel. Metals, 2021. 11(11): p. 1674.
Bahari, A., R. Lewis, and T. Slatter, Friction and wear response of vegetable oils and their blends with mineral engine oil in a reciprocating sliding contact at severe contact conditions. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2018. 232(3): p. 244-258.
Hadi, M. and R. Atefi, Effect of Minimum Quantity Lubrication with Gamma-Al. Indian Journal of Science and Technology, 2015. 8(S3): p. 130-135.
Zhang, D., et al., Specific grinding energy and surface roughness of nanoparticle jet minimum quantity lubrication in grinding. Chinese Journal of Aeronautics, 2015. 28(2): p. 570-581.
Molaie, M.M., A. Zahedi, and J. Akbari, Effect of water-based nanolubricants in ultrasonic vibration assisted grinding. Journal of Manufacturing and Materials Processing, 2018. 2(4): p. 80.
Duc, T.M. and T.Q. Chien, Performance evaluation of MQL parameters using Al2O3 and MoS2 nanofluids in hard turning 90CrSi steel. Lubricants, 2019. 7(5): p. 40.

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Study on High-Speed Machining of 2219 Aluminum Utilizing Nanoparticle-Enhanced Minimum Quantity Lubrication (MQL) Technique

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Abstract

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1. Introduction

2. Experimentation

2.1. Materials Used

2.2. Experimental Setup

2.3. MQL Dispersion Preparation

3. Results And Discussion

3.1. Surface roughness and surface micromorphology

3.2. Temperature generated during high-speed saw cutting

4. Conclusion

Declarations

References

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