M. Zlatanovic, U. Kascak, Z .Bogdanov*, Faculty of Electrical

Engineering, 11120 Belgrade, Bulevar Revolucije 73, *Nuclear Science

Institute, Vinca, Yugoslavia

The kinetics of the diffusion zone and compound layer growth during plasma nitriding of construction steel is of special importance for the subsequent hard coating deposition in duplex surface treatment. The combined diffusion/deposition technique has been successfully applied onto HSS, hot work and other steel grades of relatively high hardness, but for a broad industrial use the duplex treatment of construction steel is of crucial importance. The samples made of steel grade DIN 42CrMo4 (AISI 4140) were plasma nitrided in a nitrogen/hydrogen discharge during various time intervals in order to study the surface layer formation. The microhardness measurement, calotest, SEM, EDX, XRD back scattered electrons and metallographic examination were performed. It has been found that the "islands" of a compound zone started to growth after two minutes of nitriding, a continuous zone was formed after two hours of treatment., while the phase was detected onto layer after 20 hours of nitriding. The properties of subsequently deposited TiN coating were also analyzed.