PVD-CrAlN and TiAlN coated Si 3 N 4 ceramic cutting inserts-2. High speed face milling performance and wear mechanism study

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Abstract In the authors’ prior works, the microstructure, turning cutting performance and wear mechanisms of PVD-CrAlN and TiAlN coated silicon nitride cutting inserts on turning of gray iron were studied. In the present work, based on the authors’ former study, the effects of the cutting speed on tool life, wear mechanism and surface quality of the workpieces were studied through high speed face milling tests. The uncoated, CrAlN and TiAlN coated cutting inserts were conducted by high speed face milling of gray iron at various cutting speeds of 600 m/min~1500 m/min. The results displayed that during high speed face milling, the tool life of the PVD coated Si 3 N 4 cutting inserts decreased as the cutting speed increased. When the cutting speed reached a certain value, the tool life increased with the cutting speed increasing. During high speed face milling, no spallation failure happened to both CrAlN and TiAlN coatings, and the coatings could protect the insert substrates effectively under various cutting speeds, improving the tool life of the uncoated cutting inserts by 138–150% and 32–65%, respectively. The wear mechanisms of all three kinds of the cutting inserts by face milling of gray iron under various cutting speed were the same. The only difference was that as the cutting speed increased, the adhesive wear of the inserts increased significantly. During high speed face milling of gray iron with three kinds of inserts, the alteration relationship of machining quality with the cutting speed was similar to the tool life with the cutting speed relationship. Furthermore, when high speed face milling of gray iron was conducted, CrAlN coated Si 3 N 4 cutting inserts displayed the best machining quality, followed by TiAlN coated and the uncoated inserts, respectively.