This paper deals with basic methodology of surface evaluation of functional surfaces, which were prepared by various machining methods (turning, milling and grinding). Here are the basic 2D (profile) parameters and 3D (spatial) parameters and their properties in relation to the machined surface. Parameters of machined surfaces were obtained by CCI Lite Coherence Correlation Interferometer from Taylor Hobson and evaluated using the TalyMap Platinum software. The article further demonstrates the inappropriateness of the surface structure assessment with only the parameter Ra (mean arithmetic deviation of the profile), which is the most common method in technical practice. This methodology extends the possibilities of a comprehensive assessment of exposed surfaces of machine parts.

This paper deals with affecting of corrosion resistance of X12CrMoWVNbN10-1-1 martensitic stainless steel after plasma nitriding. This steel was subjected to plasma nitriding at lower temperature of 400 °C for 15 h in the reverse nitriding atmosphere 1H2:3N2 (l/h), tested and then compared to untreated one. The microstructure and microhardness of the untreated and nitrided stainless steel were evaluated. The anodic potentiodynamic polarization tests in neutral 2.5% NaCl deaerated solution were executed and the corrosion properties of the untreated and plasma nitrided steel samples were evaluated. The results showed a nitride layer, consisting of nitrogen rich diffusion layer but without compound layer on the surface of the plasma nitrided X12CrMoWVNbN10-1-1 stainless steel. The surface hardness of the martensitic stainless steel after plasma nitriding was increased significantly. The corrosion resistance of the X12CrMoWVNbN10-1-1 stainless steel was increased only partially. The pitting was evaluated, and the pitting coefficient was calculated. The plasma nitrided steel showed higher (more positive) corrosion potentials, lower current densities and decreased corrosion rates and pitting during electrochemical corrosion tests compared to not nitrided steel.

The paper deals with the change of selected 3D parameters of the surface texture of ground steels after application of diffusion technologies. The steel CSN 41 2050 and 34CrNiMo6 after nitriding and ferritic nitrocarburizing in gas and plasma were evaluated. Selected 3D surface texture parameters were measured by the coherence correlation interferometer Talysurf CCI Lite. The change in surface texture parameters is influenced by the preparation of the substrate, i.e. the grinding parameters and the used diffusion technology, as well as the chemical composition of the used steels (2), (3). The steels were ground with SiC abrasive papers with grain sizes of 120, 220, 600 and 1000 according to FEPA. Steel CSN 41 2050 showed the reduction of the observed surface texture parameters almost all types of surface treatments - roughness decreased. Only in the case of ferritic nitrocarburizing in gas occurred to the deterioration of surface roughness. Similar results were achieved at 34CrNiMo6 steel - ferritic nitrocarburizing in gas led to an increase of surface roughness. For other surface treatments the roughness decreased. Applied diffusion technologies increase the hardness of functional surfaces, corrosion resistance, fatigue strength, wear resistance and reduce coefficient of friction (4). The above-mentioned advantages of applied diffusion layers along with the reduction in surface roughness can contribute to wider use of these technologies in technical practice.

Austenitic stainless steels are common spread in many industries. Plasma nitriding is one of the few technologies that allows surface modification of austenitic stainless steels. In this study, a plasma nitriding method to form a hard surface layer at two different austenitic steels AISI 302 and AISI 316L. The surface morphology, chemical composition and mechanical properties of the formed layers were described and the results were compared with each other. The formed nitrided layers on both steels created a uniform multi-phase layer which was characterized by high hardness and very good abrasion resistance.

This study is focused on corrosion resistance of plasma nitrided and duplex treated (plasma nitrided and additionally zinc phosphate conversion coating) C45 carbon steel, using the NSS tests. The duplex treatment was compared to untreated, plasma nitrided (PN) and simple zinc phosphate (Znph) steel. The steel samples were plasma nitrided at a temperature of 500 °C for 15 h in the nitriding atmosphere ratio of 3H2:1N2 (l/h), the case depth reached 0,324 mm and the compound layer 6,4 mm. The additionally crystalline Znph layer composed by hopeite Zn3 (PO4) 2.H2O and by a smaller quantity of phosphophyllite Zn2Fe (PO4) 2.H2O reached approximately 6,2 mm (for all treated steel samples). The NSS tests (1000 h) proved slight corrosion improvement of PN steel (vcorr = 1.26 g/m2.h) and distinct improvement for simple Znph coating on steel (vcorr = 0.7 g/m2.h), compared to untreated one (vcorr = 1.36 g/m2.h). Very distinctive corrosion resistance was found for duplex treated steel (vcorr = 0.36 g/m2.h). Results were completed and confirmed with very good agreement by weight loss and visual evaluation.