Experimental Investigation of Tool Life and Chip Thickness Using Vegetable Oils as Cutting Fluids under MQL

Cutting fluids play a vital role in machining operations by reducing friction and heat, facilitating chip removal, and enhancing both tool life and product quality. Although mineral-based oils are commonly used in flood lubrication, their toxicity and environmental impact have raised concerns. As a result, alternative methods like dry machining and Minimum Quantity Lubrication (MQL) have gained attention for reducing oil consumption. This study investigates the use of vegetable oils as MQL cutting fluids in the turning of AISI 4130 steel, revealing that vegetable-based fluids outperform conventional options. MQL significantly improves machining efficiency compared to flood and dry conditions. The study also examines chip formation dynamics, especially in hardened AISI 4340 steel, where high temperatures and tool wear pose challenges that can be mitigated through sustainable practices like MQL with bio-based fluids. Among the oils tested, coconut oil proved to be the most effective, producing thinner chips and larger shear angles at higher cutting speeds. The findings indicate that coconut oil excels at reducing chip thickness and increasing shear angles during high-speed cutting. Future research will further compare biobased fluids with synthetic oils and dry machining to optimize processes for greater sustainability and performance. Under MQL, vegetable oils show significant performance improvements over blasocut oil, with soybean oil achieving the lowest cutting forces, reducing them by 9% compared to blasocut. It also improves surface roughness by 4.23%, 8.56%, 15.24%, and 16.98% compared to other oils. Temperature and power consumption are also reduced by 3% to 19% compared to other oils. The study emphasizes the benefits of bio-based cutting fluids in MQL, highlighting their superiority over conventional methods in terms of surface quality, tool longevity, and environmental impact.