Influência da espessura de corte equivalente e técnica de aplicação de fluido de corte na integridade da superfície do Inconel 718

Abstract

Grinding is an abrasive machining process recommended in applications requiring a high level of dimensional accuracy and better surface finish in metal components. Inconel 718 is a nickel-based superalloy that has high mechanical strength, corrosion, and creep even when they are operating at high temperatures, what justifies its application in the manufacturing of components of turbines and parts of the aeronautical engines. Differently from other materials, such as steels and cast irons, machining of Inconel 718 is impaired because of its properties such as low thermal conductivity and high chemical affinity with the main conventional abrasives for grinding wheels. This will lead to high concentration of heat in the cutting zone and consequently deterioration of surface finish of the component, among other problems. Thus, it is indispensable to employ high volume of coolant during grinding process to cool the grinding zone. However, it is growing a demand for alternatives that reduce the flow rates employed due to their high cost and difficult handling and discard. In this way, the Minimum Quantity Lubrication (MQL) coolant technique can be a viable alternative to the conventional coolant delivery technique (flood coolant), especially because of the extremely low volume of oil employed. In this sense, this work aims to contribute to the grinding of superalloys presenting results of the surface integrity of the Inconel 718 alloy after peripheral grinding operation with silicon carbide grinding wheel. The cutting parameters employed were: cutting speed of 38 m/s, workpiece speed of 10 m / min, two values of equivalent cutting thickness (0.09 and 0.18 μm) and two cutting fluid application techniques: conventional (flood) and MQL. The output variables were roughness, machined surface images via SEM, microhardness and microstructure of the workpiece material. The results showed that the roughness values were below the stipulated limit of 0.63 μm for semi-finishing grinding processes. The microhardness was influenced by the equivalent cutting thickness and cutting fluid technique employed. No changes were observed in microstructures of workpiece under the investigated conditions.