Enhancement of structural, physical and tribological behaviors of newly developed Ti–25Nb–25Mo beta-type for biomedical applications

Titanium and its alloys continue to attract the attention of biomedical researchers due to their superior biological and mechanical biocompatibilities when compared to other metallic biomaterials. Our work aims to analyze the tribological performance of Ti-alloy with a new chemical composition (50 (at.%) Ti, 25 (at.%) Mo, 25 (at.%) Nb) and production process parameter variation (Milling time, 2, 6, 12, and 18h) effects on this behavior. The microstructure, chemical analysis, surface topography, friction, and wear characteristics of milled and consolidated Ti–Nb–Mo were thoroughly investigated using OM, SEM, EDS, laser profilometer, and tribometer with an applied load of 6 N in wet conditions using 9 g/l of NaCl. The experimental results showed that all consolidated Ti–25Nb–25Mo samples have a single β-phase due to the high [Mo]_eq value of this alloy with the existence of insoluble Mo and Nb. The presence of Nb and Mo in a solid solution within the Ti-matrix can effectively improve hardness and wear resistance. In addition, it was found that as milling time extended, the average friction coefficient showed a notable rise, progressing from 0.503 at 2 h to 0.512 at 6 h and reaching the highest value of 0.564 at 12 h. Whereas the wear volume and wear rate both exhibited a similar trend of decreasing from 69.66 × 10⁴μm³ and 110.1 × 10⁻⁴ μm³ N⁻¹μm⁻¹ to 27.6 × 10⁴ μm³, 43.18 × 10⁻⁴ μm³ N⁻¹μm⁻¹ with increasing milling time from 2 h to 12 h, respectively. This enhancement in tribological behavior can be attributed to the improved mechanical and physical characteristics of the alloys presented by plastic deformation ability as well as the increased density with milling time to attain the highest value of 4.95 g/cm³ at 12h of milling. Furthermore, the primary mechanism of wear observed in the Ti–25Nb–25Mo system was abrasive wear, accompanied by adhesion wear and delamination.