Influence of pulsed bias duty cycle variations on structural and mechanical properties of arc evaporated (Al,Cr)2O3 coatings

(AlxCr1 − x)2O3 coatings were synthesised by cathodic arc evaporation applying DC and pulsed substrate bias voltages to study the impact of different bias duty cycle settings on structure and morphology as well as mechanical and tribological properties. X-ray diffraction revealed a corundum-type (AlxCr1 − x)2O3 phase structure for Al contents x ≤ 0.5 and the formation of an additional face-centred cubic (Al-Cr-O) phase for x ≥ 0.5 for the pulsed bias situation, independently of the chosen duty cycle. In general, changes of the duty cycle in the manner of decreasing the electron current time duration along with an extension of the ion bombardment during growth lead to a reduction of the coatings' domain size, the formation of compressive residual stress as well as increasing coating hardness and Young's modulus. An amorphous-like coating microstructure accompanied with diminished mechanical properties was observed when a DC substrate bias voltage was applied. The investigations illustrate the potential of tuning the properties of arc evaporated oxide coatings by adjusting the energetic particle bombardment during growth.