Effect of high-pressure coolant supply when machining nickel-base, Inconel 718, alloy with coated carbide tools

Inconel 718 was machined with a triple PVD coated (TiCN/Al2O3/TiN) carbide tool at speeds up to 50 m min(-1) using conventional and various high coolant pressures, up to 203 bar. Tool life, surface roughness (Ra), tool wear and component forces were recorded. The test results show that acceptable surface finish and improved tool life can be achieved when machining Inconel 718 with high coolant pressures. Compared to conventional coolant supplies, tool life improved as much as 740%, when machining at 203 bar coolant pressure at a speed of 50 m min(-1). Tool life generally increased with increasing coolant supply pressure. This can be attributed to the ability of the high-pressure coolant to lift the chip and gain access closer to the cutting interface. This action leads to a reduction of the seizure region, thus, lowering the friction coefficient which in turn results in reduction in cutting temperature and component forces. Chip breakability during machining is dependent on the depth of cut, feed rate and cutting speed employed as well as on the coolant pressure employed. Machining Inconel 718 with lower coolant pressures did not produce chip segmentation. Tool wear increased gradually with prolong machining with high coolant pressures. Nose wear was the dominating tool failure mode due probably to a reduction in the tool-chip and tool-workpiece contact length/area. (C) 2004 Elsevier B.V. All rights reserved.