3.2.3 Copper Decorated Zr-B and Zr-B-N Coated Steel sur
by
Copper decoration of the Zr-B and Zr-B-N coated samples showed that the peripheries of macro-particles
and craters are macro-defect sites which lead to open porosity in the coatings (Fig. 5). These sites,
crevices between the droplets and the coating and craters which are left uncoated or only thin coated due
to shadowing effects of the particle flux coming from the target, screening effects of droplets and craters,
are heavily decorated with copper. Moreover, on Zr-B coated samples widespread string-type copper
decoration was observed revealing the inherent porous structure of the coating (Fig. 6). The inherent
porosity in these coatings can be explained by the fine-columnar structure, crystallinity and high hardness
impeding stress relaxation which may result in the formation of micro-fissures [1-3]. This type of copper
stringers was not observed in Zr-B-N coatings which indicated that the sources of porosity in these
coatings were only macro-particles and craters. The absence of inherent porosity can be due to fine-
grained to amorphous structure of these coatings which prevents the formation of pinholes crossing the
film. Also the lower hardness of the Zr-B-N coatings indicates lower stresses generated on the coating
during the deposition process [1-3].
Fig. 5: SEM image of preferentially copper decorated droplet peripheries and craters on a Zr-B
coated steel.
3.2.4. Copper Decorated TiN Coated Steel
As in Zr-B and Zr-B-N coatings, the peripheries of macro-particles and craters are sources of porosity in 3.2.
TiN coated steels which showed themselves by heavy copper decoration (Fig. 7). On the other hand,
randomly distributed dense copper decoration was also observed all over the coating indicating the porous The
structure of the coating (Fig. 8). Previous studies conducted with TiN coated samples by employing the Cu’
copper decoration technique had shown that the decoration density increases with increasing substrate of -
448 Prakt. Met. Sonderbd. 26 (1995)
