Cutting performance of Al₂O₃ coatings deposited by High Speed PVD

Cemented carbide tools with Al₂O₃ coatings deposited by chemical vapor deposition (CVD) remain widely used in turning applications. However, CVD has drawbacks such as thermal cracks, tensile stress, and embrittlement due to eta phase formation. These issues drive interest in synthesizing Al₂O₃ using physical vapor deposition (PVD). Compared to significant studies dealing with the cutting performance of Al 2 O 3 coatings deposited by conventional PVD such as magnetron sputtering (MS) and arc PVD at T < 700 °C, no studies are available in this context at T > 700 °C. High-speed PVD (HS-PVD), based on hollow cathode gas flow sputtering, enables stable deposition at T ≈ 850 °C in reactive oxide environments. In this study, Al₂O₃ and TiAlN/Al₂O₃ coatings were compared to TiAlN coating in dry fine turning of C45 + N steel. Thereby, the TiAlN, as a widely used PVD tool coating, is a reference. The Al₂O₃ toplayer deposited by HS-PVD and TiAlN using MS. Al₂O₃ coatings exhibit limited tool life due to poor adhesion, highlighting the necessity of an adhesion-promoting interlayer. Wear analysis under a cutting speed of v c = 120 m/min reveals that the TiAlN/Al₂O₃-coated tools achieve a significantly longer tool life of t c = 18 min and indicate lower flank wear than TiAlN reference. Furthermore, a higher resistance to crater wear of TiAlN/Al₂O₃ coated tools compared to TiAlN under v c = 200 m/min is observed and can be attributed to the distinct thermal and chemical properties of the Al₂O₃ toplayer. This demonstrates promising work on tools coated with Al₂O₃ by HS-PVD at such high temperatures and shows their high potential in real cutting applications. • High Temperature synthesize of Al 2 O 3 coating on WC-Co tools by High Speed PVD • Enhanced crater wear of Al 2 O 3 coated tools compared to TiAlN coated ones • lower flank wear land width VB max of Al 2 O 3 coated tools compared to TiAlN variants