Author: Lisseth Katherine Ramirez Antolinez
Ramirez Antolinez, Lisseth Katherine, 2024 Design and development of novel titanium alloys with enhanced wear resistance for biomedical implant applications, Flinders University, College of Science and Engineering
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The field of biomaterials has seen significant growth, becoming a burgeoning industry and a key area of research. The widespread adoption of titanium and its alloys in biomedical applications, particularly in devices with metal-to-metal contacting parts, has been fueled by their exceptional attributes: low density, high specific strength, favorable mechanical properties, high biocompatibility, and excellent corrosion resistance. This expansion is largely driven by the demand for durable implants and prostheses that can effectively serve an aging population. Previous research has demonstrated that alloying titanium with elements like Zr, Nb, Ta, and Mo can significantly enhance its mechanical properties and biocompatibility. In this project, a series of Ti-xZr-4Nb-33Ta (x=20, 30, 40 wt.%) and Ti-30Zr-4Nb-xMo (x=10, 13, 16 wt.%) alloys were specifically designed and fabricated via casting techniques. The microstructural characteristics, mechanical properties, and wear resistance in Phosphate-Buffered Saline solution were comprehensively assessed for all six alloys, with comparisons made against the widely used Ti-6Al-4V alloy. Optical microscopy of the Ti-Zr-Nb-Ta, Ti-6Al-4V, and Ti-Zr-Nb-Mo alloys revealed homogeneous grain structures with visible pores and surface contaminants. Nanoindentation tests showed that the nanohardness values of the tested alloys ranged from 3.9 to 5.3 GPa. Among the Ta-containing alloys, Ti-20Zr-4Nb-33Ta (H = 4.5 ± 0.07 GPa) and Ti-40Zr-4Nb-33Ta (H = 4.4 ± 0.09 GPa) exhibited similar hardness values, while Ti-30Zr-4Nb-33Ta showed slightly lower hardness (H = 4.2 ± 0.17 GPa). In the Mo-containing alloys, an increase in Mo content generally correlated with an increase in nanohardness, with Ti-30Zr-4Nb-16Mo demonstrating the highest hardness (H = 5.3 ± 0.24 GPa). Young's modulus for the Ti-Zr-Nb-Ta and Ti-Zr-Nb-Mo alloys ranged from 70 to 108 GPa, all lower than the Ti-6Al-4V reference value of 120 GPa.Tribocorrosion tests at open circuit potential (OCP) showed that both Ta- and Mo-containing alloys exhibited superior wear resistance compared to Ti-6Al-4V, specifically the Ti-30Zr-4Nb-16Mo alloy demonstrated the lowest wear potentials under varying normal loads (17.5 N and 30.8 N) , indicating enhanced tribocorrosion resistance. Scanning electron microscopy (SEM) of the wear tracks revealed significant differences in wear mechanisms and track morphology under different load conditions, with higher loads resulting in increased abrasive wear and plastic deformation. The results suggest that the novel Ti-Zr-Nb-Ta and Ti-Zr-Nb-Mo developed alloys possess promising mechanical and tribocorrosion properties, making them suitable candidates for biomedical implant applications. The improved wear resistance and lower Young's modulus compared to Ti-6Al-4V indicate their potential to reduce the stress-shielding effect and enhance implant longevity. This study fills the gap in understanding the comprehensive properties of these novel alloys, providing a foundation for their future application in biomedical devices.
Keywords: Biomaterials, Mechanical properties, Wear behavior, Titanium alloys, Tribocorrosion
Subject: Engineering thesis
Thesis type: Masters
Completed: 2024
School: College of Science and Engineering
Supervisor: Reza Hashemi