High Speed Ball Nose End Milling of Inconel 718

High speed machining (HSM) using ball nose end mills, is attracting interest in the aerospace industry for the machining of complex 3D aerofoil surfaces in nickel based superalloys and titanium alloys. The paper initially reviews published data detailing the effect of cutter/workpiece orientation (±βfN and ±βf), tool coatings/materials and cutting environments (spray mist, high pressure flood, etc.) on tool performance. Experimental work is subsequently detailed aimed at determining the effect of cutter orientation, tool coating and cutting environment on tool life, tool wear mechanisms, cutting forces, chip formation, cutting temperature and workpiece surface roughness, when high speed ball nose end milling Inconel 718™.A horizontal downwards cutter orientation with high pressure cutting fluid (70 bar, 26 l/min) provided the best tool life with cut lengths of ∼15 m which were twice as long as when employing a dry cutting environment. Temperature measurements from the implanted thermocouple technique, indicated that high pressure cutting fluid application substantially reduced workpiece temperature from 320°C when cutting dry, to 175°C.