Tool life when high speed ball nose end milling inconel 718

Following a brief introduction of high speed machining (HSM) and the machinability of Inconel 718, the paper details experimental work using TiAlN and CrN coated tungsten carbide ball end mills, operating at cutting speeds up to 150 m/min. Inconel 718 is one of a family of nickel based superalloys that are used extensively for gas turbine applications requiring high temperature strength. It is an extremely difficult material to machine, not the least, because it maintains much of its strength at elevated temperatures (similar to 600 degreesC), has low thermal conductivity and is prone to work harden during cutting. A 3 factor, full factorial cutting experiment at two levels is outlined with the workpiece inclined at 45 degrees and 60 degrees from the horizontal. The longest tool life was obtained when operating at 90 m/min cutting speed with RAIN coated products. The choice of tool coating was the main factor influencing tool life. The primary tool wear mechanism was adhesive wear, which affected the CrN coating to a greater extent. This was accompanied by peeling off the coating to expose the K10 carbide substrate. Irrespective of the tool coating, notches developed close to the depth of cut position. With the work-piece orientated at 60 degreesC, greater tool deflection occurred which exacerbated notch wear and edge chipping. (C) 2001 Elsevier Science B.V. All rights reserved.