Influence of multilayer graphene platelet concentration dispersed in semi-synthetic oil on the grinding performance of Inconel 718 alloy under various machining conditions

Coolant plays an important role in grinding, as it preserves the workpiece integrity by reducing the friction, as well as cooling the surface. In grinding, the coolant is generally applied at high flow rates, through the flooding technique, which can cause health and environmental damage and moreover high costs. An alternative is to use less coolant with the addition of solid lubricant particles, which improve the tribological behavior of the fluid, such as multilayer graphene that is a small solid lubricant with high thermal conductivity. The aim of this present study is to investigate the influence of a multilayer graphene concentration (0.05 wt% and 0.10 wt%) dispersed in semi-synthetic oil applied using the Minimum Quantity of Lubrication (MQL) technique on the grinding performance of Inconel 718 alloy under various machining conditions. Graphene-free oil, flooding and dry conditions were also tested for comparison. The output parameters evaluated were: surface roughness, microhardness, residual stresses, grinding power and SEM images. The cooling-lubrication fluid properties (viscosity and thermal conductivity) were also obtained. The results showed that grinding with the lowest graphene concentration in the milder condition provided the lowest roughness values and microhardness variation, required about 50% less grinding power, inhibited surface crack generation, led to smoother surfaces and resulted in compressive residual stress.