1. Laser Surface Modified
TI 6Al-4V
By
Milan van Bree
TU Delft 2008.

2. Objectives
 The objectives are:
• Understand the materials for implant design
• Understand surface modification
• Understand the role of microstructure
• Research if microstructure changes corrosion
resistance
• Research which microstructure is optimal

3. Outline
 Introduction
 Purpose of the Research
 The Research
 Summary
 Conclusion

4. Introduction
 The goal of orthopedic implants
give people another chance at
mobility.
 What happens when these
implants fail or corrode?
 What can we as engineers do?

5. Engineering Implants
 The main component for implant design
has been material selection.
• Stainless steel
• Titanium
• Cobalt
 Titanium has become very popular due
to its good: biocompatibility, high
strength, and bone adhesion.

6. Titanium Implants
 Titanium implants still have issues that
are being addressed.
• Poor wear resistance
• Harmful wear and corrosion products
• Aluminum- Neurotoxin
• Vanadium- Cytotoxin
 How do we eliminate or reduce these
problems with titanium?

7. Understanding Titanium
 First, we must understand what makes titanium
corrosion resistant.
• The formation of a tenacious oxide layer
• Close to the cathodic end of the galvanic series
 Second, we must find a solution to improving
the corrosion resistance.
• Oxide thickening
• Nitriding
• Surface re-melting

8. Issues with Coatings
 The oxide thickening and nirtiding
method have promising results but not
without consequence.
• Hard and brittle
• Crack and flake off easily when force is
applied
 That leaves us with laser surface
re-melting or modification.

9. Laser Surface Modification
 Laser surface modification allows for the
surface to retain most of the base
materials properties.
 The change that does occur comes from
the morphing of the microstructure.
 The change is made in two ways:
• Surface melting
• Surface heat treating

10. Titanium Microstructures
 Titanium depending on its
alloys comes in three
forms.
• Alpha phase (HCP)
• Beta phase (BCC)
• Alpha-beta phase (Mixed)
 Titanium 6AL-4V is a
alpha-beta phase alloy.
This means that it is heat
treatable.
Hexagonal Closed-Packed (HCP)
Body Centered Cubic (BCC)

11. Understanding the Microstructure
 The microstructure of Ti-6Al-4V can still
come in a variety of structures.

12. Understanding the Role of the
Microstructure
 We have shown that laser surface
melting and heating has improved
the corrosion resistance of
TI-6Al-4V.
 Credit has been given to oxide
thickening.
• Validity issue with microstructure
change
Open Circuit Potentials Vs. Time

13. What About Microstructure?
 Other research has made the argument
that the refinement and change in
microstructure are to be given credit.
• Validity with oxide layer formation
 The question then becomes, regardless
of the oxide layer which microstructure is
the most corrosion resistant?

14. Current Plan of Research
 We are currently researching the effect of
microstructure of corrosion resistance.
 We have currently mapped out the boundary
line for melting and heat treating for laser
processing.
 Due to limited funds we are only looking at
three microstructures.
• As received condition
• Laser melted condition
• Laser heat treated condition

15. Current Plan of Research
 After the treatment of each sample the
samples will have the oxide layer removed and
then subjected to corrosion tests.
 If a certain microstructure performs better then
a change in corrosion resistance can be linked
to microstructure.
 If this is the case then more research will be
needed to determine the optimal
microstructure for titanium implants.

16. Summary
 Titanium implants have issues that need
addressed.
 Changing the microstructure of the
titanium implant may help resolve these
issues.
 More research is needed to understand
the role of the microstructure of titanium
implants on corrosion resistance.

17. Conclusion
 As more research is performed on the
corrosion resistance of titanium
microstructures, we as engineers will be
able to better design and produce higher
quality titanium implants.

18. References
 Gaggl A, Schultes G, Muler WD, Karcher H. Scanning electron
microscopical analysis of laser-treated titanium implant
surfaces-a comparative study. Biomaterials 2000; 21:1067-
1073.
 Gyorgy E, Perez del Pino A, Serra P, Morenza JL. Surface
nitridation of titanium by pulsed Nd:YAG laser irradiation.
Applied Surface Science 2002; 186:130-134.
 P, He XL, Li XX, Yu LG, Wang HM. Wear resistance of a laser
surface alloyed Ti-6Al-4V alloy. Surface and Coatings
Technology 2000; 130:24-28.
 Mori JC, Serra P, Martinez E, Sardin G, Esteve J, Morenza JL.
Surface treatment of titanium by Nd:YAG laser irradiation in the
presence of nitrogen. Applied Physics A 1999; 69:S699-S702.