Comprehensive characterisation and testing of WS2 nanoparticle reinforced minimum quantity lubrication

Managing the heat generation during the machining of difficult-to-cut materials is crucial for extending tool life and improving the surface integrity of the machined components. Nano lubricant minimum quantity lubrication (NMQL) is proposed as an effective method for reducing heat generation and improving heat removal from the cutting zone. The presence of nanoparticles within the base oil has the potential to increase the heat transfer capabilities of the oil and reduce the friction between the tool and workpiece. Tungsten disulfide (WS2) is a promising nanoparticle for this application as its low coefficient of friction, high thermal conductivity and low toxicity make it ideal for machining of difficult-to-cut materials, such as Inconel 718. This paper presents the first study into how the addition of WS2 nanoparticles affects the properties of the base rapeseed oil based on first principles in terms of friction coefficient, contact angle, and convective heat transfer. Moreover, the impact of these changes in lubricant properties on machining performance was demonstrated by a set of machining experiments in end milling of aerospace-grade superalloy, Inconel 718. The addition of WS2 nanoparticles led to a ~ 33% decrease in the coefficient of friction and over 13.2% increase in convective heat transfer coefficient compared to the base oil. When testing machining performance, WS2 reinforced MQL was found to decrease cutting forces with a maximum reduction of 14.4% for WS2 (4 wt%) at 50 ml/h and a maximum increase in tool life of 36.8% for WS2 (4 wt%) at 150 ml/h, compared to flood cooling. These improvements highlight the potential for WS2-based NMQL to reduce the number of tools used for the production of advanced aerospace components, leading to lower manufacturing costs and environmental impacts associated with cutting tools and the use of critical raw materials such as tungsten and cobalt.