In aerospace manufacturing, grinding remains a vital precision machining method, particularly for challenging materials like titanium alloys, nickel-based alloys, and high-strength steel, which represent over 60% of all processing operations.
However, conventional mineral cutting fluids used in these grinding processes are increasingly problematic. They are derived from non-renewable resources and contribute to environmental degradation through oil mist and harmful particulate matter, affecting both worker health and manufacturing costs, which can account for 18% to 21% of total expenses.
Minimum quantity lubrication (MQL) employing biolubricants, which are biodegradable and non-toxic oils derived from vegetable or animal sources, has shown promise in reducing fluid usage by more than 90%. Yet, the widespread application of biolubricants in grinding aerospace alloys is limited due to a lack of understanding regarding how their physicochemical characteristics influence grindability. Issues such as excessive tool wear, workpiece surface burning, and wheel clogging hinder industrial adoption.
To address these challenges, a collaborative research team from the School of Mechanical and Automotive Engineering at Qingdao University of Technology, the State Key Laboratory of Ultra-precision Machining Technology at The Hong Kong Polytechnic University, and the College of Mechanical and Electrical Engineering at Nanjing University of Aeronautics and Astronautics, among others, has published a study titled “Comparative Assessment of Force, Temperature, and Wheel Wear in Sustainable Grinding Aerospace Alloy Using Biolubricant.”
This study provides a systematic review of the application of biolubricant MQL in grinding typical aerospace materials that are difficult to machine. It particularly focuses on the mechanisms by which the physicochemical properties of biolubricants—such as molecular structure, viscosity, surface tension, pH, pour point, and thermal stability—affect grindability, encompassing aspects like grinding force, temperature, wheel wear, and workpiece surface integrity.
The research indicates that biolubricants with long carbon chains, high fatty acid saturation, and polar groups enhance the adhesion of lubricating oil films. While high viscosity improves lubrication, it can also restrict cooling and wheel cleaning. Conversely, low surface tension enhances wettability and heat transfer. The pour point and thermal stability are critical in determining the adaptability of biolubricants under extreme conditions, while the pH value has implications for workpiece surface corrosion.
Experimental validations confirm that biolubricants significantly outperform traditional mineral oils in terms of lubrication and cooling capabilities. Further advancements are seen with nano-enhanced biolubricants, which utilize the rolling antifriction properties of nanoparticles to enhance performance and heat transfer. Additionally, the combination of hybrid nano-enhancers, such as CNTs-MoS2, with vegetable oil-water mixtures and wheel cleaning jet technology helps to improve cooling and lubrication coordination while maintaining wheel cleanliness.
The paper “Comparative assessment of force, temperature, and wheel wear in sustainable grinding aerospace alloy using biolubricant” is authored by Xin Cui, Changhe Li, Yanbin Zhang, Wenfeng Ding, Qinglong An, Bo Liu, Hao Nan Li, Zafar Said, Shubham Sharma, Runze Li, and Sujan Debnath. The full text of this open-access study can be accessed at this link.
