Effect of the substrate temperature and bias voltage on the properties of ZrO2/Al2O3 coatings produced by pulsed magnetron sputtering and filtered vacuum arc deposition

The influence of deposition parameters (substrate temperature and bias voltage) on the properties of ZrO2– Al2O3 coatings (composition, microstructure, hardness, adhesion, and wear coefficient) was studied. The properties of the coatings that were produced by Pulsed-DC Magnetron Sputtering (PMS) were compared to those prepared by Filtered Vacuum Arc Deposition (FVAD). The coatings were deposited on Si and WC substrates at temperatures, Td of 25–500 °C and biases, Vb, floating and down to –200 V. The PMS deposition rate was 0.15±0.01 nm/s, while that of FVAD was 10±2 nm/s. X-ray diffraction indicated that PMS coatings had a stabilized cubic-ZrO2 structure at all Td when Vb ≤ -50 V or a tetragonal-ZrO2 structure at Vb ≥ -100 V. FVAD coatings had a stabilized tetragonal-ZrO2 structure at all Td and Vb. Coatings deposited on unheated substrates by both PMS and FVAD at floating potential had low hardness, <10 GPa. However, increasing Td to 370 °C increased the hardness of both PMS and FVAD coatings to 16±1 GPa. In the FVAD coatings, a further increase of Td to 500°C raised the hardness to 22±1 GPa. The maximum hardness, 25.9±2.6 GPa, was achieved at Vb=– 150 V (PMS coatings, unheated substrate) and was partly due to an increase in compressive stress (1066 MPa). The coating adhesion increased with Td, reaching more than 100 N at Td = 500°C (FVAD coatings, Vb=-50 V). aNRC-Negev, P.O.Box 9001, Beer-Sheva 84190, Israel bAdvanced Coatings Center, Rotem Industries Ltd., Mishor Yamin, D.N. Arava 86800, Israel cElectrical Discharge and Plasma Laboratory, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, Israel *Corresponding author