The Effect of In Situ Boron Reinforcement on the Microstructure and Tribological Performances of a Biocompatible Ti-30Zr-10Ta Alloy Fabricated by Powder Metallurgy

This study investigates the impact of in situ boron reinforcement on a biocompatible Ti-30Zr-10Ta alloy produced by powder metallurgy for biomedical applications. This research focused on understanding the influence of boron content (0 to 5 wt.%) on the microstructure, mechanical properties, and tribological behavior of the alloy. The main results showed that increasing boron additions progressively decreased the relative density of the sintered samples. Microstructural analysis via X-ray diffraction (XRD) revealed that the base Ti-30Zr-10Ta alloy exhibited a dominant β-Ti phase with the presence of orthorhombic α″ martensite. The addition of boron led to the in situ precipitation of various borides, specifically TiB, TiB2, TaB, and TaB2. Further characterization revealed that the microhardness was enhanced up to 19.6% with lower boron additions, maintaining the elastic modulus of the alloys. Tribological tests demonstrated a significant improvement of 25.7% in wear resistance because of the reinforcement with lower amounts of boride particles. However, higher amounts of boron resulted in a reduction in hardness and elastic modulus at the surface level of 47.2 and 49.3%, respectively, an increase in porosity, and the formation of three-body particles, which contributed to more severe wear and decreased more than twice the wear resistance of the alloy. This research successfully determined the threshold value in a maximum of 0.5 wt.% of boron additions for in situ reinforcement of a biocompatible Ti-30Zr-10Ta alloy suitable for load-bearing applications.