IMPROVEMENT OF A-C-H FILM ADHESION BY INTERMEDIATE LAYERS AND SPUTTERCLEANING PROCEDURES ON STAINLESS-STEEL, ALUMINA AND CEMENTED CARBIDE

The adhesion of amorphous hydrogenated carbon (a-C:H) films deposited in a radio frequency (r.f) plasma discharge on stainless steel, alumin a and cemented carbide with different intermediate layers (Ni, Ti and TiC) and sputter cleaning procedures was studied. The composition of t he carbon films and the intermediate layers as well as the interface b etween the coating and the substrate was determined by secondary ion m ass spectroscopy (SIMS). The adhesion experiments were carried out usi ng a scratch tester. Tested specimens were also studied by scanning el ectron microscopy (SEM) to reveal the morphology of the coatings and t he scratches. Without any intermediate layer, the a-C:H coatings gener ally had insufficient adhesion to the substrate materials studied. For stainless steel and cemented carbide substrates, the TiC intermediate layer and, for alumina substrates, the titanium intermediate layer ga ve the best adhesion values evaluated by the scratch test. Also, the s putter cleaning of the substrates prior to deposition was necessary fo r sufficient adhesion of the coating. The intermediate layers also cha nge the failure mode of the coating in the scratch test in some cases. (C) 1997 Elsevier Science S.A.