Lubrication and Grinding Characteristics of Electrostatically Charged Cutting Fluid Aerosol

In grinding, the airflow barrier generated by high-speed rotating grinding wheels restricts lubricant access to the grinding zone. Despite its high fluid throughput, flood lubrication suffers from poor penetration caused by this barrier, together with excessive resource consumption and environmental pollution. Conventional minimum quantity lubrication (MQL), assisted by compressed air, can partially overcome the airflow barrier and offers environmental benefits; however, its inherently inadequate droplet wetting and penetration still lead to insufficient cooling and lubrication, resulting in workpiece burn and low machining accuracy, particularly for difficult-to-cut materials. This study investigated electrostatic minimum quantity lubrication (EMQL), which integrates MQL with electrostatic spraying to improve droplet wetting, penetration, and grindability. An EMQL grinding system was constructed for machining GCr15 die steel, and the surface tension and contact angle of droplets were measured at different charging voltages. The effects of voltage polarity and magnitude on workpiece surface characteristics and overall grinding performance were then investigated. The results showed that increasing the absolute charging voltage reduced the surface tension and contact angle of the charged droplets and improved their penetration capability. Under the optimal condition of +8 kV, the surface microhardness decreased by up to 16.86%. Compared with conventional MQL, EMQL reduced the tangential and normal grinding forces, the grinding temperature, and the surface roughness by 58.52%, 37.54%, 22.22%, and 30.58%, respectively, and increased the grinding ratio by 31.36%. EMQL improves lubrication and heat transfer by enhancing droplet wetting and penetration, and the positive electrostatic field further optimizes grinding performance by regulating the surface microstructure and reducing microhardness.