2025 Independent Studies Highlight Power of Supercritical CO₂ Combined With MQL

In the ever-evolving landscape of CNC machining, the quest for improved efficiency, sustainability, and precision continues to drive innovation. Recent studies have explored the potential of supercritical carbon dioxide (scCO₂) combined with minimum quantity lubrication (MQL) as a transformative cooling and lubrication strategy. These notable research papers shed light on the significant advantages of this approach, particularly in the machining of titanium alloys, which are widely used in aerospace, medical, and dental applications.

Study 1: Tool Wear and Productivity Impact of scCO₂ + MQL

The first study, titled "The tool wear and productivity impact of CO₂ and emulsion-based cooling when milling diverse titanium alloys," conducted by Proud et al., investigates the effects of scCO₂ + MQL on tool wear and productivity during the milling of various titanium alloys.

The research highlights that scCO₂ + MQL not only reduces tool wear significantly but also enhances tool life and productivity across different titanium alloys. Key findings from this study include:

• Extended Tool Life: The use of scCO₂ + MQL resulted in a remarkable increase in tool life, with improvements of up to 338% for Ti-6Al-4V at 170 m/min and a 205% increase for Ti-5Al-5Mo-5V-3Cr at 90 m/min compared to traditional emulsion cooling. For commercially pure titanium, scCO₂ + MQL led to a 43% longer tool life at 330 m/min.
• Higher Surface Speeds: The study demonstrated that scCO₂ + MQL allows for increased surface speeds, leading to higher material removal rates and improved manufacturing productivity. Specifically, for 25 minutes of tool life, scCO₂ + MQL enabled an increase in cutting speed of 8.6% for commercially pure titanium, 34.7% for Ti-6Al-4V, and 42.7% for Ti-5Al-5Mo-5V-3Cr.
• Reduced Wear Mechanisms: The research identified a shift in wear mechanisms, with scCO₂ + MQL leading to more uniform wear patterns and less chipping, ultimately preserving tool integrity. The study noted that the cooling and lubrication provided by scCO₂ + MQL effectively mitigated wear progression, resulting in a smoother wear pattern compared to emulsion cooling.

Study 2: Sustainable Cooling in Dental Applications

The second study, "Sustainable and Efficient Cooling in Titanium Milling for Dental Applications: A Study on Supercritical CO₂ + MQL with Focus on Tool Wear and Surface Topography," authored by Siahsarani et al., focuses on the application of scCO₂ + MQL in the milling of titanium dental implants. 

This research emphasizes the eco-friendly and efficient nature of scCO₂ + MQL in precision machining. Key insights from this study include:

• Significant Reduction in Tool Wear: The study reported a reduction in tool wear by over 190% when using scCO₂ + MQL compared to emulsion cooling, particularly during extended milling operations.
• Enhanced Surface Quality: Surfaces machined with scCO₂ + MQL exhibited smoother finishes and less material adhesion, which is crucial for dental applications where precision is paramount. The surface roughness values (Sa) obtained with scCO₂ + MQL were 8-15% lower than those with emulsion cooling, indicating its effectiveness in preserving surface integrity.
• Increased Material Removal Rates: The use of scCO₂ + MQL allowed for a 68% increase in material removal rates and a 40% reduction in cutting time, showcasing its potential for enhancing productivity without compromising quality.

The Power of Supercritical CO₂ in CNC Machining

Both studies underscore the transformative potential of scCO₂ + MQL in CNC machining, particularly for challenging materials like titanium alloys. The unique properties of supercritical CO₂, which behaves as both a gas and a liquid, enable superior cooling and lubrication, leading to improved tool life, reduced wear, and enhanced surface integrity.

As industries increasingly prioritize sustainability and efficiency, the adoption of scCO₂ + MQL presents a compelling solution that aligns with these goals. By minimizing CNC coolant usage and eliminating harmful residues, this innovative approach not only enhances machining performance but also contributes to greener manufacturing practices.

In conclusion, the integration of supercritical CO₂ in CNC machining represents a significant advancement in the quest for improved productivity and sustainability. As further research and development continue in this area, the potential for scCO₂ + MQL to revolutionize machining processes is becoming increasingly evident, paving the way for a new era of efficient and eco-friendly manufacturing.