Análise de desempenho do processo de retificação do aço SAE 52100 em diferentes condições de lubri-refrigeração

Abstract

Grinding aims to provide combination of tight dimensional and geometric tolerances to a given component. Among its characteristics, great amount of heat is conducted to workpiece during the process, especially when using conventional abrasive grinding wheels, so the use of cutting fluid is indispensable. However, due to current worldwide policy regarding sustainable machining processes, it is important to search for alternatives to reduce the consume of coolants. Among some alternatives, the minimum quantity lubrication (MQL) technique stands out, although presents some limitations in grinding process such as its poor efficiency in reducing cutting temperatures and the tendency of grinding wheel clogging, especially when using high viscosity oils. For this reason, many attempts to improve the efficiency of the MQL technique have been carried out, highlighting the addition of solid particles in the oils. It has been reported that solid particles dispersed in coolants can improve cooling capacity of coolants and provide better tribological conditions during grinding, thereby improving grinding performance. In this context, this work aims to analyze the performance of surface grinding of SAE 52100 hardened steel with conventional alumina grinding wheel under different cutting and cooling-lubrication conditions, including two types of cutting fluids (semisynthetic and synthetic) delivered via conventional (flood) and MQL technique, as well as different graphene concentrations dispersed in the fluids. The output variables used to assess the grinding performance were the surface roughness and images of ground surface, microhardness and microstructure beneath machined surface, electric power, specific energy and cutting region temperature. The results showed that grinding with the MQL technique provided similar or even better results in comparison to the conventional technique, especially with respect to surface finishing and microhardness variation beneath machined surface. Also, the graphene performance showed to be strongly dependent on its concentration and fluid type, and the best results in terms of surface finishing were observed after grinding with combination of lowest graphene concentration and semisynthetic cutting fluid. Furthermore, the addition of graphene in the cutting fluid positively affected the microhardness, microstructure and cutting region temperature results.