Effects of coating materials on the machinability of a nickel base, C-263,alloy

PVD coated (TiN/TiCN/TiN, TiAlN and TiZrN) and uncoated carbide tools were used to machine a nickel base, C-263, alloy at high-speed conditions. The t est results show that the multiple TiN/TiCN/TiN coated inserts gave the bes t overall performance in terms of tool life when machining at cutting speed s up to 68 m min(-1) and at depths of cut of 0.635: mm, 1.25 mm and 2.54 mm . All. the tool grades tested gave fairly uniform surface roughness (Ra) va lues, below the rejection criterion, at lower speed conditions. The TiZrN c oated inserts gave the lowest component forces when machining at lower cutt ing speed conditions while the TiAlN coated inserts gave the lowest compone nt forces wizen machining at a higher speed of 68 m min(-1) and depth of cu t of 1.25 mm. This tool performance can generally be attributed to the diff erence in their ability to provide effective lubrication at the cutting zon e, thermal conductivity of the coating materials as well as the cutting con ditions employed. The uncoated carbide tools generally encountered; more se vere crater weal; chipping/fracture of the cutting edges as well as pronoun ced notching during machining, This is due to their inability to provide ef fective lubrication at the cutting zone, thus impeding the gliding motion o f the chips along the rake and flank faces respectively, thus accelerating, flank wear. Analysis of the worn tool edges revealed adhesion of a compact "fin-shaped" structure of hardened burrs with saw-tooth like edges. This g enerally alters the initial geometry of the cutting edge, consequently resu lting to poor surface finish with prolonged machining.