Influence of deposition parameters on microstructure and mechanical properties of chemical vapor deposited Ti1-xAlxN coatings

Using thermally activated chemical vapor deposition (CVD), it is possible to synthesize Ti1-xAlxN coatings with Al contents up to x > 0.8 in a face-centered cubic crystal structure. This is considered to be due to their quite high global Al content and due to the frequently observed self organized nanolamellar microstructure consisting of lamellae with high Al contents of x > 0.9 epitaxially stacked with lamellae where x similar to 0.5. However, CVD is a complex process and the formation mechanism of the lamellae and the resulting coating properties are not yet fully understood. Here, we have investigated the impact of the deposition temperature, deposition pressure and rotation speed of the reactive gas feed on the microstructure and mechanical properties. Our results show that by varying the pressure between 10 and 185 mbar and the temperature between 700 and 820 degrees C the grain size and texture can be tailored. In addition to the amount of wurtzitic AlN formed, they govern the mechanical properties. Similarly, the nanolamella periodicity strongly depends on temperature and pressure, indicating that the reaction kinetics are responsible for their formation rather than the gas feed rotation.

Automated summary

Using thermally activated chemical vapor deposition (CVD), Ti1-xAlxN coatings with Al contents up to x > 0.8 can be synthesized due to their high global Al content and self organized nanolamellar microstructure. However, the formation mechanism of the microstructure and the resulting coating properties are not fully understood. The study investigates the effects of deposition temperature, pressure, and gas feed rotation speed on the microstructure and mechanical properties.