New application of ionic liquid as a green-efficient lubricant

Abstract

In the present work, it has been attempted to use ionic liquid as a green and compatible additive to base cutting fluid for the grinding process. Grinding forces in tangential and normal directions and the surface quality of the Inconel 718 superalloy were determined as a criterion for comparing the results, and the cutting parameters, such as the wheel rotation speed, workpiece speed, and cutting depth, were also selected as variable parameters in three levels. The experimental results showed that, in addition to the compatibility issue of the ionic liquids, the normal force in the case of ionic-liquid and mineral-based lubricants was declined by approximately 49.3 % than that of non-used cutting fluid technique. By increasing cutting depth from 20 to 60 μm, workpiece speed from 1000 to 3000 mm/min, and wheel speed from 10 to 30 m/s led to an increase of 168 % and 139 %, 46 % and 38 %, and 167 % and 78 % in normal and tangential forces, respectively. The results showed that the grinding forces reduced and the surface integrity of the workpiece improved when using ionic liquid as an additive compared to the mineral-based one. The reason of this superiority can be attributed to the more tendency of liquid molecules to adhere to the surface of the superalloy and form a strong lubricant layer with a lower static contact angle, compared to the mineral-based fluid, which leads to the creation of stable lubrication conditions in the high-stress grinding affected zone. The static contact angle of the DI water was approximately 62 °, while by changing the droplet type to mineral-based fluid and ionic liquid, the CA value was diminished to 51 ° and 38 °, respectively, with reducing rate of 18 %, and 39 %. In addition to experimental study, mathematical models were also developed to predict the grinding forces and surface roughness by means of response surface methodology (RSM). The result of analysis of variance (ANOVA) showed that the fitted models have high accuracy compared to the experimental results.