Influence of Dopants in Oxide-based Coatings Deposited by Thermal CVD

The deposition of hard coatings with chemical vapor deposition (CVD) is a way to improve the performance of cemented carbide cutting tools, where Al2O3 coatings show advantages in many applications. Further improvements of the coating properties can be achieved by doping of Al2O3. Hence, within this thesis the influence of seven different doping elements in Al2O3 coatings was investigated. The coating experiments were conducted in a vertical hot wall reactor between 450 °C and 1000 °C. The HCl/Ar/N2/H2/CO2 deposition atmosphere was also varied and the addition of CH4 and NH3 was investigated. Cemented carbide with three different precoatings and molybdenum were used as substrate material. Gravimetric analyzes, X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and hardness measurements (nanoindentor) were used for coating characterization. The dopants were incorporated up to 20 at.% in the coating and influenced coating morphology, crystal structure, hardness and texture.