This paper presents the experimental results in terms of
surface integrity when turning a CoCrMo alloy in dry
conditions regarding to biomedical applications.
Experimental observations reported in this study point
out that dry turning is a pursuing lubricating strategy that
may generate economic advantages for surgical implants
manufacturers due to the reduction of cleaning processes
and the amount of used lubricant to dispose with a view
to sustainability. The effects of the cutting speed and
feed rate on surface integrity were evaluated in terms of
surface topography, surface roughness, residual stresses,
micro-hardness measurements, and microstructure
alterations. Further studies will analyse different cutting
conditions and the effect of the tool wear on surface
integrity to fill the lack of literature. The main outcomes
can be summarized as follows:
The feed rate played the major role on the surface
roughness: smoother surfaces resulted for a feed rate of
0.1 mm/rev, while not regular surfaces resulted for a
feed rate of 0.15 mm/rev. The cutting speed effect
influenced the shape of the feed marks, and more
uniform surface profiles resulted for a cutting speed of
60 m/min due to less chipping and notching of the
cutting edge.
For a cutting speed of 40 m/min, a higher density of long
grooves due to the tungstencarbide particles resulted,
while at higher cutting speed a higher density of folds,
tears and interrupted feed marks resulted due to higher
temperature. At increasing the feed rate, the chip
morphology changed and entanglement around the
workpiece resulted, therefore a higher density of adhered
chip fragments on the surface resulted.
XRD analysis showed that high compressive stress
resulted on the surface for all the cutting conditions, and
a small reduction of stress level is observed at a depth of
compressive stresses due to higher strain rate, while the
cutting speed has an inverted effect due to the increment
of the cutting temperature.
The effect of the turning process resulted in a deformed
sub-surface layer along the cutting direction, and a grain
refinement is appreciable. The strain hardening induced
a surface hardening of the material with a radial
gradient, which increases at increasing the cutting
parameters.