Study on grinding of inconel 625 and 718 alloys with cutting fluid enriched with multilayer graphene platelets

Abstract

Nickel-based superalloys present excellent thermo-mechanical properties that can be maintained at high temperatures, making them suitable for application in aerospace and nuclear industries. Such components require a combination of superior surface finish and tight dimensional tolerances, thus grinding is the first option. However, these properties demand high specific energy during grinding and cause rapid grinding wheel wear, that adversely affects the ground surface hence leading to poor grindability. Thus, a proper selection of a cooling-lubrication technique is indispensable to reduce the friction and cool the grinding wheel-workpiece interface, thereby avoiding thermal damage that compromises workpiece surface integrity. In contrast, the use of cutting fluids in high volumes must be discouraged due to their harmful impact to environmental and human healthy. In this sense, research for improving eco-friendly techniques such as minimum quantity lubrication (MQL) in grinding have been increased, and the application of cutting fluids with solid particles dispersed on it have shown promising results. In this context, this work aims to analyze the surface finish and morphology of two nickel-based superalloys (Inconel 625 and Inconel 718) after grinding with semi-synthetic environmentally friendly oil enriched with multilayer graphene (MLG) platelets delivered via MQL technique. Surface roughness (Ra, Rz, Rsk and Rku parameters), images via scanning electron microscope (SEM), cutting power and grinding force ratio were the output parameters analyzed. The results for Inconel 718 showed that presence of the MLG promoted reduction in Ra and Rz, a better surface morphology and negligible effect on the other output parameters. With respect to the Inconel 625, on the other hand, the use of MLG platelets did not show any benefits in terms of surface finish, with evidence of occurrence of intense plastic deformation at machined surface (micro-plowing wear mechanism), although significant reduction in grinding force ratio was observed.