*2.2. Sources of Documents*

The comparison of different journals and the number of documents in the journals can be seen in Table 1. Among other journals, the highest number of papers have been published in the *International Journal of Advanced Manufacturing Technology*, with a total of 106 articles. After that, the second highest number of publications has been in the *Journal of Cleaner Production*, with a total of 101 articles; the lowest number of articles has been in the *Wear* journal, i.e., 15 articles. It can be deduced from the analysis that most of the articles targeted the sustainability and machinability aspects of the different metalworking fluids, and therefore a limited number of articles have been published that examine the wear characteristics.

**Table 1.** Most relevant sources and their number of published articles.


### *2.3. Word Cloud*

To pictorially illustrate the representation of the different keywords used in the different articles related to metalworking fluids and sustainable machining operation, a word cloud highlighting the different keywords is shown in Figure 3. It can be seen from the figure that the most frequently used keywords are "cutting tools", "minimum quantity lubrication", "sustainable development", etc. Therefore, it can be inferred by the word cloud that a considerable amount of research work has been conducted on transforming conventional machining operation to a more sustainable machining operation through the adoption of different strategies such as nanofluids, minimum quantity lubrication, dry machining, and vegetable oils, among others.

**Figure 3.** Pictorial representation of the most frequently used keywords.

From the scientometric analysis, it is evident that a considerable amount of research has been carried out in the area of metalworking fluids for the development of machining and different sustainable techniques and is still in progress. Therefore, considering the substantial amount of research output, a comprehensive review is needed which summarizes the impact of mineral oil-based MWFs, comparing it with its counterparts (i.e., vegetable oil-based MWFs) and also shedding light on the different sustainable machining techniques available in the market.

This paper reviews the adverse effects of mineral oil-based MWFs and compares it with vegetable oil-based MWFs, highlighting the tribological performances of the vegetable oil-based MWFs. The paper also highlights the potential of other sustainable machining operations such as dry machining, high pressure coolant technique, minimum quantity lubrication, and the potential use of nanofluids in machining operations.
