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s P e c I A L<br />
A L U M I N I U M s U r f A c e<br />
Abb. 3: DLC-Beschichtungen aus diamantartigem Kohlenstoff vereinen Härte mit<br />
Reibfestigkeit<br />
damage (scratches) over almost the<br />
whole surface of the skirt during the<br />
same lifetime. The result was a spectacular<br />
breakthrough for the Bekaert<br />
team. Improvements of up to two<br />
percent of the output power and exten<strong>de</strong>d<br />
lifetime were <strong>de</strong>monstrated<br />
by an engine test with the Kawasaki<br />
ZX0R engine.<br />
The test clearly illustrated that by<br />
improving the surface finish (going<br />
against the common un<strong>de</strong>rstanding<br />
that a certain roughness is nee<strong>de</strong>d for<br />
a good operation of the piston) and introducing<br />
a customised coating stack,<br />
a DLC coating can be <strong>de</strong>posited on an<br />
aluminium piston, showing obvious<br />
improvements in both friction reduction<br />
and lifetime extension.<br />
Fig. 3: Diamond-like carbon (DLC) coatings combine high hardness with low friction<br />
2) to look into more <strong>de</strong>tail. A magnification<br />
of 50 revealed small scratches<br />
on the surface. Research has shown<br />
these are plastic <strong>de</strong>formations of the<br />
piston skirt, due to the low hardness<br />
of the substrate material. Nevertheless,<br />
the Bekaert team stated this does<br />
not lead to flaking of the coating. The<br />
results excee<strong>de</strong>d all expectations, as<br />
an uncoated piston shows very heavy<br />
Authors<br />
Mark Boghe is Product Market Manager<br />
Automotive/Racing worldwi<strong>de</strong> at Bekaert.<br />
Marc Hervé is Market Manager Racing,<br />
Europe at Bekaert.<br />
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ALUMINIUM · 11/2008<br />
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