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Combined FIB technique with acoustic microscopy to detect steel-DLC interface defects

: Bernland, K.; Köhler, B.; Zinin, P.V.; Fei, D.; Rebinsky, D.A.


Diamond and Related Materials 15 (2006), No.9, pp.1405-1411
ISSN: 0925-9635
Journal Article
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()
microscopy; FIB; SEM; scanning acoustic microscopy; coating

In this work, focused ion beam (FIB) technique was employed to characterize subsurface defects in chromium-containing DLC (Cr-DLC) coatings. Subsurface defects as small as one micron were successfully detected in a flat Cr-DLC coated steel coupon by scanning acoustic microscopy (SAM). The nature of the subsurface defects in the coating was investigated by repeated FIB milling and a scanning electron microscopy (SEM) imaging technique where element analysis was done by Energy Dispersive X-ray spectroscopy (EDX). It has been found that defects are located mostly at the DLC steel interface. A model for the bump-like defects is proposed based on the SAM, EDX and FIB measurements. Model is that of a delamination/void between Cr layer and steel substrate. The existence of these defects at the interface leads to the defects visible on the surface of the DLC coating; bumps or pits which are larger in diameter compared to the subsurface defects.