Electrochemical and mechanical behavior of laser processed Ti–6Al–4V surface in Ringer’s physiological solution

Laser surface modification of Ti–6Al–4V with
an existing calcium phosphate coating has been conducted
to enhance the surface properties. The electrochemical and
mechanical behaviors of calcium phosphate deposited on a
Ti–6Al–4V surface and remelted using a Nd:YAG laser at
varying laser power densities (25–50 W/mm
2
) have been
studied and the results are presented. The electrochemical
properties of the modified surfaces in Ringer’s physiolog-
ical solution were evaluated by employing both potentio-
dynamic polarization and electrochemical impedance
spectroscopy (EIS) methods. The potentiodynamic polar-
izations showed an increase in the passive current density
of Ti–6Al–4V after laser modification at power densities
up to 35 W/mm
2
, after which it exhibited a decrease.
A reduction in the passive current density (by more than an
order) was observed with an increase in the laser power
density from 25 to 50 W/mm
2
. EIS studies at the open
circuit potential (OCP) and in the passive region at 1.19 V
showed that the polarization resistance increased from
8.274 9 10
3
to 4.38 9 10
5
X cm
2
with increasing laser
power densities. However, the magnitudes remain lower
than that of the untreated Ti–6Al–4V at OCP. The average
hardness and modulus of the laser treated Ti–6Al–4V,
evaluated by the nanoindentation method, were deter-
mined to be 5.4–6.5 GPa (with scatter \±0.976 GPa)
and 124–155 GPa (with scatter \±13 GPa) respectively.
The corresponding hardness and modulus of untreated
Ti–6Al–4V were *4.1 (±0.62) and *148 (±7) GPa respec-
tively. Laser processing at power densities [35 W/mm
2 enhanced the surface properties (as passive current density is reduced) so that the materials may be suitable for the bio-medical applications.