The tribological behavior of boron nitride (BN) doped zirconia (ZrO2) ceramics

In this study, the impact of hexagonal boron nitride (BN) addition at various ratios on the sinterability, microstructure, mechanical, and tribological properties of zirconia (3Y-ZrO2) ceramics stabilized with 3 mol% Y2O3 was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro vickers hardness testing, a ball-on-disk type wear device, and a profilometer. After sintering at 1250°C for 2 hours, the density of 3Y-ZrO2 samples with a 0.25% BN addition increased from 5.16 g/cm³ to 5.52 g/cm³, improving their sinterability. With the addition of BN and an increase in the amount of additive, an increase in the grain size of 3Y-ZrO2 occurred; the average grain size rose from 0.12 µm to 0.42 µm with a 1% BN addition. While the hardness of 3Y-ZrO2 samples with a 0.25% BN addition increased from 714 Hv to 978 Hv, a decrease in hardness was observed beyond this proportion. Wear tests of BN-added 3Y-ZrO2 samples were conducted under dry sliding conditions at room temperature with 5 and 10 N loads using commercially obtained WC ceramic balls. With the addition of BN and an increase in the amount of additive, the coefficient of friction and wear volume of 3Y-ZrO2 have significantly decreased. The average coefficient of friction and wear volume of pure 3Y-ZrO2 under a 10 N load were 0.2 and 1.6 mm³, respectively, whereas these values decreased to 0.1 and 0.32 mm³, respectively, in 3Y-ZrO2 with 1% BN addition. This reduction is attributed to BN's inherent solid lubricating property. Consequently, the addition of BN has resulted in a significant increase in the wear resistance of 3Y-ZrO2. These results show that 3Y-ZrO2 ceramics with low amounts of BN can be used as a potential material, especially in dental implants and other biomedical applications.