Corrosion and tribological behaviors of spark plasma sintered Ti-Nb-Ta-Cr-Co _0.2 and Ti-Nb-Ta-Fe _0.35 -Co _0.35 HEAs in simulated body fluid for hard tissue implants

High-entropy alloys (HEAs) are progressively accepted in biomedical fields due to their remarkable mechanical strength, resistance to corrosion, and compatibility with biological systems. In this study, the electrochemical and tribological performances of two novel biomedical HEAs (Ti-Nb-Ta-Cr-Co 0.2 and Ti-Nb-Ta-Fe 0.35 -Co 0.35 ) were evaluated and compared with the existing Ti-6Al-4V implant. Corrosion assessments were conducted in simulated body fluid (SBF) using electrochemical techniques, yielding significantly lower corrosion rates for the developed HEAs. The corrosion rates for the sintered Ti-Nb-Ta-Cr-Co 0.2 and Ti-Nb-Ta-Fe 0.35 -Co 0.35 HEAs were determined to be 7.401 × 10 −4 and 9.754 × 10 −4 mm/year, respectively, both significantly lower than the rate of Ti-6Al-4V alloy (2.961 × 10 −3 mm/year). This enhanced corrosion resistance is vital for prolonged biomedical applications. Tribological testing in the presence of SBF was performed under a reciprocating sliding motion with a zirconia counter material. The tribological test demonstrated significantly reduced wear rates for the developed HEAs. The Ti-Nb-Ta-Cr-Co 0.2 HEA recorded the lowest wear rate of 4.44 × 10 −8 (mm 3 /mm) at a 10 N load, while the Ti-6Al-4V shows the maximum wear rate compared to the developed HEAs under all loading conditions. The exceptional wear resistance of the HEAs is ascribed to their unique microstructural stability and the synergistic effects of multi-principal elements enhancing hardness. Examination of the worn surfaces of the sintered HEAs and Ti-6Al-4V revealed phenomena such as adhesion, oxidation, abrasion, delamination, and wear debris. Based on the findings, the developed HEAs demonstrate potential as superior alternatives for hard tissue replacement in comparison to the traditional Ti-6Al-4V.