METALLIC INTERLAYERS BETWEEN STEEL AND DIAMOND-LIKE CARBON

Many processes for the deposition of diamond-like carbon (DLC) are car ried out just above room temperature. The low process temperature make s it simple to coat a wide variety of materials but can lead to seriou s adhesion problems between the coating and the substrate. In this wor k DLC coatings on steel for tribological applications were developed. DLC was deposited on stainless steel (DIN 1.4305) by pulsed laser abla tion of graphite. Generally the adhesion of DLC on steel was very poor . By applying different metallic interface layers (e.g. Cr, Mo, Si, Cu ), the adhesion has been improved considerably. The microstructure of the interfaces has been studied by cross-sectional transmission electr on microscopy, including high resolution imaging and electron diffract ion, but no evidence for a crystalline reaction zone was observed. The adhesion of the coating has been tested by ultrasonic cavitation and the scratch test. A rank order of intermediate layer metal combination s was established. Generally the combination of Cu and a metal belongi ng to one of the IVb, Vb or VIb groups of elements was observed to giv e good adhesion. Cu/Cr appeared to give the best adhesion.