UDC 621.162 © Bogdan Bogdanski, Ewa Kasprzycka ESTIMATION OF THE ADHESION OF THE Cr C+(Ni-Mo) TYPE DUPLEX LAYERS TO THE STEEL BY MEANS OF SCRATCH TEST The paper presents the results of examinations of the structure and mechanical properties of CrC+(Ni-Mo) type duplex layers produced by vacuum chromizing of tool steel surface covered with Ni-Mo alloy electrolytic coating. <...> Investigations of layers thickness, their morphology, phase composition, hardness, depth profiles of elements in the layer diffusion zone have been conducted. <...> It has been proved, that the adhesion of CrC+(Ni-Mo) type duplex layers to steel base is better than that of the CrC carbide layers, produced directly on the steel surface without any electrolytic coating. <...> INTRODUCTION This paper concerns diffusion layers, with carbide structure, manufactured during the vacuum chromizing process, joined with preliminary galvanic treatment. <...> Modification of diffusion layer’s phase structure, used to increase corrosion resistance, can be performed e.g. through electrolytic covering of the steel base with nickel, prior to diffusion process [3-7]. <...> It is also known that small addition of molybdenum to steel prevents pitting corrosion, which occurs e.g. in NaCl water solutions [8]. <...> During one’s own research about vacuum chromizing process, the modif ication of phase structure (of chromium carbide layers) was conducted through electrolytic covering of steel surface with the Ni-Mo alloy, prior to diffusion process [6]. <...> CrC+(Ni-Mo) duplex coatings acquired through this modif ication, were characterized with higher corrosion resistance, while simultaneously keeping their high friction wear resistance [7]. <...> This paper presents the assessment of adhesion of manufactured layers, with the use of scratch test. 2. <...> CrC+(Ni-Mo) duplex layers were created in the vacuum chromizing process on tool steel X210Cr12 base, covered electrolytically with the Ni-Mo alloy, which contained 70% Ni and 30% Mo. Thickness of electrolytic coating was 5 m. <...> For comparison, there were also manufactured carbide layers CrC, which were obtained directly on the X210Cr12 steel’s surface, without electrolytic coating. <...> Depth profiles of elements concentration of the CrC+(Ni-Mo) type duplex layer Проблемы машиностроения <...>