HARDNESS OF PLASMA NITRIDED LAYERS CREATED AT DIFFERENT CONDITIONS

The plasma nitriding is a method of surface hardening using d.c. glow discharge to improve elemental nitrogen to the surface of steel with subsequent diffusion into the bulk of material. Generally, two layers are created during plasma nitriding process. The compound layer is consisted of eFe2-3N and γ-Fe4N phases. This type of layer has been very hard, but unfortunately brittle with good friction and anticorrosion properties. The thickness and hardness of γ -Fe4N depends on quantity and quality of nitride-formed elements. The composition of nitrided layers can be effectively influenced by chemical composition of nitriding atmosphere. The carbon alloy steels have been generally used in automobile industry for their high hardness and strength. Low corrosion resistance sometimes limits their industrial application. Plasma nitriding process is a chemical-heat treatment widely used to increase the surface hardness, fatigue strength, wear and corrosion resistance of steels. Parameters of plasma nitriding layer are not dependent only on process parameters of nitriding, such as duration, temperature, pressure, voltage and nitrogen potential, but also dependent upon the substrate alloy type and in this case of selected alloy on their microstructure. The aim of study was to research the creation of nitrided layer inside the cavity with the diameter of 6 and 8 mm at pressure 4 mbar. This study deals with mechanical properties of nitriding layers inside the cavities after plasma nitriding process.