Design of Comb Crack Resistant Milling Inserts: A Comparison of Stresses, Crack Propagation, and Deformation Behavior between Ti(C,N)/α-Al₂O₃ and Zr(C,N)/α-Al₂O₃ CVD Coatings

• Main Authors: Maiara Moreno, Idriss El Azhari, Daniel Apel, Matthias Meixner, Wei Wan, Haroldo Pinto, Flavio Soldera, Frank Mücklich, José García
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Crystals
• Subjects: milling inserts; comb crack wear; polycrystalline CVD coatings; in-situ synchrotron X-ray diffraction; micro-mechanics; residual stress engineering
• Online Access: https://www.mdpi.com/2073-4352/11/5/493
• ISSN: 2073-4352

Investigations on comb crack resistance of milling inserts coated with chemical vapor deposition (CVD) Ti(C,N)/α-Al₂O₃ and Zr(C,N)/α-Al₂O₃ showed a distinct wear evolution in both systems. Wear studies revealed that the appearance of comb cracks is connected to the initial CVD cooling crack network. Micropillar compression tests indicated a brittle intergranular fracture mechanism for the Ti(C,N) layer and a transgranular fracture accompanied with signs of plastic deformation for the Zr(C,N) coating. Additionally, for the Zr(C,N) based system, a compressive stress condition in the temperature range of interest (200–600 °C) was determined by in-situ synchrotron X-ray diffraction. The set of residual compressive stresses together with the ability of the Zr(C,N) layer to deform plastically are key features that explain the enhanced resistance to comb crack wear of the Zr(C,N) based system in milling of cast iron.