Experimental Results on Lamellar-Type Solid Lubricants in Enhancing Minimum Quantity Lubrication Machining

Author(s):  
Trung Kien Nguyen ◽  
Kyung-Hee Park ◽  
Patrick Y. Kwon

This paper studies the effect of various lamellar-type solid lubricants (graphite and hBN) that can be mixed into a lubricant to potentially improve the machinability of minimum quantity lubrication (MQL) machining. To examine this, the solid lubricants are classified into particles and platelets based on their aspect ratios as well as their respective sizes. In particular, the particles are classified into microparticles and nanoparticles based on their dimensions (average radius), while the platelets were classified, based on their average thickness, into two types: the “microplatelets” if the thickness is typically up to few tens of microns and the “nanoplatelets” if the thickness is well below a tenth of a micron (even down to few nanometers). Our previous work has shown that the mixture of an extremely small amount (about 0.1 wt. %) of the graphitic nanoplatelets and vegetable oil immensely enhanced the machinability of MQL machining. In this paper, many lubricants, each mixed with a particular variety of nano- or micro-platelets or one type of nanoparticles, were studied to reveal the effect of each solid lubricant on MQL machining. Prior to the MQL machining experiment, the tribological test was conducted to show that the nanoplatelets are overall more effective than the microplatelets and nanoparticles in minimizing wear despite of no significant difference in friction compared to pure vegetable oil. Consequently, the MQL ball-milling experiment was conducted with AISI 1045 steel yielding a similar trend. Surprisingly, the oil mixtures with the microplatelets increased flank wear, even compared to the pure oil lubricant when the tools with the smooth surface were used. Thus, the nanoscale thickness of these platelets is a critical requirement for the solid lubricants in enhancing the MQL machining process. However, maintaining the nanoscale thickness is not critical with the tools with the rough surfaces in enhancing the MQL process. Therefore, it is concluded that finding an optimum solid lubricant depends on not only the characteristics (material as well as morphology) of solid lubricants but also the characteristic of tool surface.

Author(s):  
Trung Kien Nguyen ◽  
Patrick Y. Kwon ◽  
Kyung-Hee Park

The lamellar-type solid lubricants are readily available in a form of platelets. The diameter and thickness of these platelets are typically up to tens of microns and few microns, respectively, which are classified as micro-platelets. Some of these platelets are also available as nano-platelets whose thickness is well below a micron (even to few nanometers). In the previous work, the vegetable oil mixed with nano-platelets was enormously effective for Minimum Quantity Lubrication (MQL) machining. Clearly, the micro-platelets are not as inexpensive. In addition, the mixtures with the micro-platelets are not as stable as those with the nano-platelets. This paper intends to find the effect of the thickness differential on these platelets in MQL machining. The tribometer test shows that the nano-platelets are much more effective than the micro-platelets in reducing wear without changing the friction. With the MQL ball mill experiment, the micro-platelets present in MQL oil increased the tool wear, even compared to the traditional MQL with pure oil only. Thus, the thickness of the nano-platelets holds an important characteristic to enhance MQL-based machining.


Author(s):  
Trung Nguyen ◽  
Dinh Nguyen ◽  
Pete Howes ◽  
Patrick Kwon ◽  
Kyung-Hee Park

Improving the machinability of titanium (Ti) alloys remains unresolved for manufacturing industries because excessive tool wear and catastrophic tool failures lead to shortened tool life and low productivity with any available cutting tool system. Besides optimizing the substrate and/or coating materials for cutting tools, improving the cooling and lubricating conditions is one of the ways to improve the machinability of Ti alloys. In this paper, we explore the possibility of using a nano-platelet, lamellar-type solid lubricant of graphite Exfoliated graphite nano-platelets (xGnP®) grade C750 (or xGnP750) in Minimum Quantity Lubrication (MQL) machining of Ti-6Al-4V (Ti64). Due to the lamellar or layered crystal structure, each layer easily slides against adjacent layers to provide the lubricity when introduced at the tool/work material interface. Although the nano-platelets have a nano-thickness, they have a micro-sized diameter, which prevents the nano-platelets from penetrating through human skin and breathing through nose. This makes the great advantage in this approach compared to other nano-enhanced MQL processes. The milling experiment shows that the nano-platelets present in the MQL oil decreased flank wear and improved the tool life compared to traditional MQL with pure oil as well as dry machining. The presence of nano-platelets reduces the micro chipping and tool fracture caused by the effect of impact in interrupted machining.


2020 ◽  
Vol 13 ◽  
Author(s):  
Gaurav Gaurav ◽  
Abhay Sharma ◽  
G S Dangayach ◽  
M L Meena

Background: Minimum quantity lubrication (MQL) is one of the most promising machining techniques that can yield a reduction in consumption of cutting fluid more than 90 % while ensuring the surface quality and tool life. The significance of the MQL in machining makes it imperative to consolidate and analyse the current direction and status of research in MQL. Objective: This study aims to assess global research publication trends and hot topics in the field of MQL among machining process. The bibliometric and descriptive analysis are the tools that the investigation aims to use for the data analysis of related literature collected from Scopus databases. Methods: Various performance parameters are extracted, such as document types and languages of publication, annual scientific production, total documents, total citations, and citations per article. The top 20 of the most relevant and productive sources, authors, affiliations, countries, word cloud, and word dynamics are assessed. The graphical visualisation of the bibliometric data is presented in terms of bibliographic coupling, citation, and co-citation network. Results: The investigation reveals that the International Journal of Machine Tools and Manufacture (2611 citations, 31 hindex) is the most productive journal that publishes on MQL. The most productive institution is the University of Michigan (32 publications), the most cited country is Germany (1879 citations), and the most productive country in MQL is China (124 publications). The study shows that ‘Cryogenic Machining’, ‘Sustainable Machining’, ‘Sustainability’, ‘Nanofluid’ and ‘Titanium alloy’ are the most recent keywords and indications of the hot topics and future research directions in the MQL field. Conclusion: The analysis finds that MQL is progressing in publications and the emerging with issues that are strongly associated with the research. This study is expected to help the researchers to find the most current research areas through the author’s keywords and future research directions in MQL and thereby expand their research interests.


2020 ◽  
Vol 997 ◽  
pp. 85-92
Author(s):  
Abang Mohammad Nizam Abang Kamaruddin ◽  
Abdullah Yassin ◽  
Shahrol Mohamaddan ◽  
Syaiful Anwar Rajaie ◽  
Muhammad Isyraf Mazlan ◽  
...  

One of the most significant factors in machining process or metal cutting is the cutting tool performance. The rapid wear rate of cutting tools and cutting forces expend due to high cutting temperature is a critical problem to be solved in high-speed machining process, milling. Near-dry machining such as minimum quantity lubrication (MQL) is regarded as one of the solutions to solve this problem. However, the function of MQL in milling process is still uncertain so far which prevents MQL from widely being utilized in this specific machining process. In this paper, the mechanism of cutting tool performance such as tool wear and cutting forces in MQL assisted milling is investigated more comprehensively and the results are compared in three different cutting conditions which is dry cutting, wet cutting (flooding) and MQL. The MQL applicator is constructed from a household grade low-cost 3D printing technique. The chips surface of chips formation in each cutting condition is also observed using Scanning Electron Microscopy (SEM) machine. It is found out that wet cutting (flooding) is the best cutting performance compare to MQL and dry cutting. However, it can also be said that wet cutting and MQL produced almost the same value of tool wear and cutting forces as there is negligible differences in average tool wear and cutting forces between them based on the experiment conducted.


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