Synergistic improvement of HA and LaB6 on the bio-tribological properties of Ti6Al4V alloy fabricated by laser direct energy deposition

This study introduced rare earth boride (LaB6) and bioactive ceramic (HA) to enhance the bio-tribological properties of Ti6Al4V alloy fabricated by laser direct energy deposition (LDED). The methods and instruments such as optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), Vickers hardness tester, and UMT-3 tribometer were employed to examine the microstructure, phase composition, microhardness, and bio-tribological properties. The results showed that the La2O3 and network-like TiBw formed through in-situ reactions, and the distribution of La2O3 at the grain boundaries facilitated grain refinement through Zener pinning; Yet, the addition of HA weakened the effect of grain refinement. Besides, the microhardness was not significantly changed due to the promoting effect of P element on the formation of beta-Ti and large grains. Furthermore, under the phosphate buffered saline (PBS) environment, a tribofilm containing phosphate on the worn surface formed, leading to a remarkable improvement in the bio-tribological properties. This study provides valuable insights for the further application of Ti6Al4V in orthopedic implants.