Mechanical properties of single and polycrystalline α-Al2O3 coatings grown by chemical vapor deposition
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External Organisational units
- Ceratizit Austria GmbH
- Christian Doppler Laboratory of Advanced Coated Cutting Tools
Due to the highly anisotropic mechanical properties of corundum, the lifetime of α-Al 2O 3 coated cutting tools is strongly influenced by its texture. However, limited literature is available on orientation dependent mechanical properties of α-Al 2O 3 coatings. Thus, in the present study, (0001), (11-20), (1-102) oriented single crystalline α-Al 2O 3 coatings and a state of the art (0001) textured polycrystalline α-Al 2O 3 coating were synthesized using chemical vapor deposition (CVD) on sapphire and cemented carbide substrates and the mechanical properties were investigated. The morphology of the coatings was studied by scanning electron microscopy and the respective orientation verified by electron backscatter diffraction. The (0001) oriented α-Al 2O 3 single crystalline coating yielded a slightly higher hardness of 34.4 ± 2.0 GPa compared to the other oriented coatings. Also, the maximum Young's modulus was observed for the (0001) oriented α-Al 2O 3 single crystalline coating, with a value of 451 ± 25 GPa. Furthermore, micromechanical tests were carried out to determine the fracture stress and fracture toughness, where the (11-20) oriented single crystalline coating exhibited the highest values of 11.2 ± 0.4 GPa and 4.1 ± 0.2 MPa m 1/2, respectively. Compared to the (0001) oriented single crystalline coating, the state of the art (0001) textured polycrystalline coating exhibits lower hardness, Young's modulus, fracture stress and fracture toughness values.