Abstract
α-Al2O3 coatings have been deposited by evaporation of Al in an anodic arc with a growth rate of ~ 5 μm·h−1 at 640°C under the conditions of low ionization of the Al vapors and an increased concentration of atomic oxygen, which has been achieved by the use of a hollow anode.Intensive (current density up to 15 mA·cm−2) low-energy (50 eV) ion bombardment has provided deposition of adhesive single-phase nanocrystalline (50–150 nm) α-Al2O3 coatings with a thickness of up to 10 μm with low intrinsic stresses (1.5 GPa) and low microstrains of the crystal lattice (less than 0.1%). The composition of the discharge plasma has been determined using the optical spectroscopy method. The effect of the O2 flow and the hollow anode current on the growth rate of the alumina coatings has been investigated and it has been shown that the increasing degree of O2 dissociation promotes an increase in the growth rate of coatings.
Highlights
High-rate synthesis of thick α-aluminium oxide (α-Al2O3) coatings using reactive PVD methods at low temperatures requires solving a number of tasks related to the creation of conditions for the nucleation of the α-phase on the substrate and subsequent rapid growth of α-Al2O3 coating with a dense and fairly homogeneous microstructure and low levels of intrinsic stresses that provide a firm joint between the thick coating and substrate.The parameters of intense ion assistance needed for decreasing the temperature of synthesis of αAl2O3 coatings strongly affect the phase composition, microstructure and level of intrinsic stresses in the coating [1]
Abstract. α-Al2O3 coatings have been deposited by evaporation of Al in an anodic arc with a growth rate of ~ 5 μm h-1 at 640°C under the conditions of low ionization of the Al vapors and an increased concentration of atomic oxygen, which has been achieved by the use of a hollow anode.Intensive low-energy (50 eV) ion bombardment has provided deposition of adhesive single-phase nanocrystalline (50–150 nm) α-Al2O3 coatings with a thickness of up to 10 μm with low intrinsic stresses (1.5 GPa) and low microstrains of the crystal lattice
As the deposition rate grows, it is required to increase the density of ion assistance current, and so more research is needed in order to assess the potential implementation of this approach
Summary
The parameters of intense ion assistance needed for decreasing the temperature of synthesis of αAl2O3 coatings strongly affect the phase composition, microstructure and level of intrinsic stresses in the coating [1]. When the substrate temperature decreased, the required ion energy increased and amounted to 150 eV at 700°C. Treatment by ions with energy in the range 100–200 eV range leads to the growth of lattice microstrains and an increase in the level of intrinsic stresses in the coating [3]. As the deposition rate grows, it is required to increase the density of ion assistance current, and so more research is needed in order to assess the potential implementation of this approach
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