LASER PROCESSING OF ORTHOPEDIC BIOMATERIALS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 272

9.3.4 Laser Processed Titanium Boride Reinforced Ti - Nb - Zr - Ta
Metal - matrix Composites 304

9.3.4.1 Wear Resistance of Titanium Alloys and Titanium
Matrix Composites

304

9.3.4.2 Titanium Boride Reinforced Ti - Nb - Zr - Ta Composites 305

9.3.4.3 Tribological Behavior of Ti - Nb - Zr - Ta + TiB Composites 309

9.3.4.4 Summary of Ti - Nb - Zr - Ta + TiB Composites 317

9.4 Conclusions 318

9.5 Future Perspectives 319

Acknowledgments 319

References 320

9.1 OVERVIEW

In the area of load-bearing orthopedic implant applications, both novel metallic
and non-metallic biomaterials as well as novel processing technologies can have
a substantial impact. While there has been a signifi cantly large volume of research
in recent years on the development of novel titanium alloys, especially based on
the beta phase of titanium, for implant applications there has been rather limited
research on the development and application of newer processing technologies
for fabricating such implants. The newer generation beta titanium alloys that are
being actively researched for biomedical applications typically contain com-
pletely biocompatible (non-toxic) alloying elements such as niobium, zirconium,
tantalum, molybdenum, iron, and tin. These alloys also exhibit a substantially
lower elastic modulus that is much closer to that of bone (10- 40 GPa) as com-
pared with the previous generation alloys, such as Ti-6Al-4V.
On the processing side, while orthopedic implants are conventionally fabri-
cated using traditional metal-working processing technologies such as casting and
forging, the advent of novel processing technologies such as direct deposition of
metallic powders using a laser-based deposition process (for example, the laser
engineered net shaping or LENS™ process) can substantially impact implant
fabrication. Thus, while traditional processes are typically subtractive in nature
with material being removed (machined) from a big block of metal into the fi nal
shape of the implant, processes such as LENS™ based on additive manufacturing
permit the fabrication of a three-dimensional near-net shape component directly
from a computer-aided design fi le in a single step. Furthermore, the use of
laser-deposition based additive manufacturing also allows for the fabrication
of custom-designed compositionally and functionally graded implants with site -
specifi c properties, a concept that can revolutionize the processing of orthopedic
implants.
In this chapter, some of the salient features of laser-deposition of orthopedic
biomaterials will be discussed. In addition to the processing aspects, the core of
this chapter is devoted to the properties of laser-deposited beta titanium alloys
and metal-matrix composites, in the context of their suitability for use in orthope-
dic implants.