Improvement in friction and wear characteristics using CaF2 as a solid lubricant at different conditions

During machining, adequate cooling and lubrication is much needed to reduce friction, wear, and temperature by efficient heat dissipation resulting in improved surface quality and longer tool life. The various alternative approach developed to provide lubrication and cooling includes minimum quantity lubrication, cryogenic cooling, and machining with the use of solid lubricants. The efficiency of solid lubricant particles greatly depends on the particle size, the wt% of solid lubricant, and base fluid used to prepare a lubricant mixture. Therefore, an attempt has been made in the present investigation, to evaluate the tribological properties of CaF₂ with different grain sizes and weight ratios in a base oil. Results demonstrated the anti-wear and friction ability of CaF₂ as a solid lubricant by improving the tribological properties of sliding surfaces. An increase in friction coefficient is observed with larger grain size (30 and 50 μm) with 10 and 20 wt% of CaF₂ as compared with 10 μm particle size. Results also showed the ability of solid lubricant particles with smaller particle sizes (10 μm) to maintain a thin film of lubrication. As a comparison, CaF₂ mixed with a base oil performed equally well compared to MQL under different loading conditions. The reduction in friction coefficient and wear is observed with solid lubricant application due to its excellent lubricity even at higher load and pressure. The analysis shows the presence of wear on disc surface in the form of visible grooves and wear debris in dry and MQL condition whereas lubricating effects of CaF₂ is dominant.