PROPERTIES OF DUPLEX COATINGS PREPARED BY PLASMA NITRIDING AND PVD TI-C-H DEPOSITION ON X20CR13 FERRITIC STAINLESS-STEEL

Duplex-coating procedures consisting of plasma nitriding and Me-C:H ha rd coating lead to an improved performance of the devices because the Me-C:H coating is supported by the nitrided phase and, therefore, the 'eggshell-effect' is avoided. Furthermore, this support leads to a hig her load-bearing capacity of the thin film. Two standard procedures (c lassical high-pressure plasma nitriding and unbalanced magnetron sputt ering of Ti-C:H) were performed subsequently to prepare the duplex coa tings on X20Cr13 ferritic stainless steel. The corrosion resistance of the steel could be improved by nitriding at 450 degrees C compared to the untreated ferritic substrate. The roughness is determined by the nitriding step. The weakest point of the coating is the transition zon e between the nitrided and the untreated substrate and not the interfa ce between the Ti-C:H coating and the nitrided substrate as shown by t he Rockwell and scratch tests. The adhesion of the duplex structure (p lasma nitriding and Ti-C:H coating) on X20Cr13 (230 HV0.1) is superiou r to the adhesion of Ti-C:H on hardened 100Cr6 ball-bearing steel (62 HRC approximate to 820 HV0.1, not nitrided). (C) 1998 Elsevier Science S.A. All rights reserved.