Experimental studies and CFD simulation of the internal cooling conditions when drilling Inconel 718

When drilling the superalloy Inconel 718 twist drills are faced with high thermomechanical loads. Owing to the low thermal conductivity of the workpiece material a large amount of the generated heat has to be transported away from the tool by the coolant. In this paper, the influence of the coolant pressure and the diameter of the coolant channels have been studied. The experiments have been supported by using computational fluid dynamics (CFD) simulations and were focused on the tool wear and the bore quality. The CFD simulation is a valuable tool which supported the present investigation, that a higher mass flux has no advantage regarding tool life and bore quality; moreover, the modification of the channel diameters has not reduced the thermal loads. In all investigated processes, dead zones near the cutting edge and the counter edge could not be reduced by increasing the flow rate. Only by the use of higher coolant pressures, the tool life could be significantly increased, as well as the bore quality. The investigations prove that especially when metrological methods reach their limits, the CFD is a suitable tool; which supports the design process effectively by giving a better insight into the coolant flow resulting from the complex drilling processes. (C) 2016 Elsevier Ltd. All rights reserved.