International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In this study, the tribological behavior of new generation cast irons (SiNb and SiW) developed as an alternative to cast irons containing high silicon and molybdenum (SiMo) is investigated under dry friction conditions. All cast irons are produced by sand mold casting as Y blocks according to ASTM A536-84 standard and metallurgical characterization studies have revealed that they all have spheroidal graphite and dispersed carbides like Mo-rich M6C, Nb-rich MC and W-rich M6C type depending on the alloying element, within a ferritic matrix. Although no significant change is observed in the spherical morphology of graphite in cast iron matrices, a significant change is observed in the amount of graphite and image analysis studies reveal that the graphite content (area-%) in SiNb and SiW cast irons is 4,02 and 4,30, respectively, compared to SiMo cast iron (5,80). A significant change in the hardness of cast irons is also determined depending on the microstructural features; SiNb (228 ± 7 HV10) and SiW (218 ± 5 HV10) cast irons have higher hardness values compared to SiMo cast iron (192 ± 5 HV10). Cast irons and alumina ball as counterpart material are subjected to a tribological interaction for 150 m under dry friction conditions at a nominal load of 10 N and a ball sliding speed of 0.08 m/s and the findings indicate that (i) the coefficient of friction (CoF) decreases as the graphite content increases, with SiMo having the lowest CoF (0.023), followed by SiW (0.025), and SiNb showing the highest CoF (0.040), (ii) the specific wear rate increases as the hardness decreases, therefore, SiMo has the highest specific wear rate, whereas SiNb demonstrates the lowest specific wear rate and (iii) adhesive wear is the dominant wear mechanism for all ductile cast irons due to the presence of their ferritic matrix.

In this research work, results of the ion plasma nitriding of the ferritic steel AISI 430F are presented . From the raw material solid bar ф35 were machined specimens with the following dimension 20x20x15. Prepared specimens were plasma nitrided in the installation ION-20. According to research plan the temperatures of 430, 480 and 530 0C, and nitriding times of 3, 6 and 9 hours were used. Nitriding gas for this experiment was ammonia Pulsed direct current was used for the nitriding.
After performing of the ion plasma nitriding process, experimental specimens were subjected to different investigations, mainly microstructural and tribological. Main facilities used for investigations are: device for determination wear resistance “ball-on-disc” (Nanovea), 3D profilometer for surface roughness determination, Optical Microscope Leits and SEM JEOL for microstructural investigations, XRD spectrometer (Rigaku RINT Ultima+) and Vickers microhardness tester for the microhardness measurement. Investigations confirmed that depending of the process parameters different characteristics of nitride layers were obtained. The following characteristic values important for the analysis of the nitride layer was obtained: specific wear rate, volume lost, friction coefficient, width of the wear path, type of wear, type of structure of the nitride layer and maximal hardness of the nitride layer. Performed investigations confirmed that ion plasma nirtriding improve surface properties of the investigate specimens compered with untreated specimen of the raw material. The effect of ion plasma nitriding is directly influenced by the nitriding parameters i.e. temperature and time of the nitriding process.