Sebastian Balos

The influence of honing process parameters on surface quality, productivity, cutting angle and coefficients of friction

Purpose – The purpose of this paper is to explore the influence of tool kinematics parameters on surface roughness, productivity and cutting angle for grey cast iron cylinder liners machined by normal honing.Design/methodology/approach – For experimental investigation, a long stroke honing system was used. Diamond and SiC tools were used, for pre‐ and finishing, respectively. The values of cutting parameters were varied within the following limits: cutting speed vs=0.931‐1.11 m/s; specific pressure of pre‐honing process pd=1.0‐1.4 N/mm2 and specific pressure of finishing honing process pz=0.2‐0.5 N/mm2. The analysis of dispersion was conducted for determining the mathematical model for cutting parameter influence on surface roughness and productivity.Findings – Dispersion analysis proved that the most influential parameters on maximum roughness depth are cutting speed for D181 tool and specific pressure of finishing honing for D151 tool. The most influential parameter on productivity in the honing process...

Modification of cellulose and rutile welding electrode coating by infiltrated TiO2 nanoparticles

In this paper, a novel method of infiltration of TiO2 nanoparticles into the coating of the cellulose and rutile shielded metal arc welding electrode is shown. Tensile properties and strength of weld metals were correlated to the chemical composition of the weld metals, ferrite type, and non-metallic inclusion type, size and composition. As infiltration time is increased in the cellulose electrodes, the non-metallic inclusion count increases and their size decreases. They act as inoculants and lead to the replacement of Widmanstaetten with the finegrained acicular ferrite which increases the mechanical properties of the welds. The modification of rutile electrodes with low and medium infiltration time also refines the microstructure and increases the mechanical properties. Specimens welded with rutile electrodes infiltrated at maximum duration exhibited the lowest mechanical properties due to the relatively large non-metallic inclusions that act as void nucleation sites and the appearance of large grain allotriomorphic ferrite in the weld metal.

Austempering kinetics of Cu-Ni alloyed austempered Ductile Iron

The aim of the paper was to investigate the effect of austempering parameters (time and temperature) on the microstructure and mechanical properties of ADI alloyed with 1.5% Cu and 1.6% Ni (in wt.%) in order to establish the optimal processing window. It was shown that the strength, elongation and impact energy strongly depend on the amounts of ausferritic ferrite and retained austenite. A processing window was established according to the results of the kinetics of the isothermal transformation. The results show that the processing window for ADI alloyed with Cu and Ni at 350 °C was relatively wide, while the processing window for the isothermal transformation at 400 °C becomes narrower and shifted to the left. The processing window of ADI austempered at 300 °C is also narrower, but shifted to the right towards the longer times compared to the processing window of ADI austempered at 350 °C.

Improvement of hardfacing process of cobalt based alloys using nanoparticles

In this paper, the application of TiO2 nanoparticles in hardfacing of hard, chemical resistant, cobaltbased alloys, is studied. The hardfacing of structural steel specimens are carried out with manual shielded metal arc welding process. The consumables were nickel chromium alloy as a buffer layer and the cobalt alloy for finishing layer. Two types of electrodes for hardfacing the control specimen were used. First was commercial, unmodified electrode, and second was the same electrode, but modified with TiO 2 nanoparticles in water solution. Infiltration of nanoparticles was carried out in three different durations of 30 seconds, 4 minutes and 8 minutes. The metallographic analysis in cross-section of the hard-faced layer, were carried out. Also, the wear resistance test was done in order to study the influence of the infiltrated nanoparticles. Rezime: U radu je obrađena problematika primene nano čestica TiO2 pri navarivanju tvrdih, hemijsko otpornih legura na bazi kobalta. Uzorci od konstrukcionog čelika su prvo navareni ručno – elektrolučnim postupkom sa dodatnim materijalom, legurom nikla i hroma (podloga), nakon čega je izvršeno navarivanje legure kobalta. Izvršeno je navarivanje kontrolnog uzorka, komercijalnim, nemodifikovanim elektrodama, kao i elektrodama koje su modifikovane infiltracijom nanočesticama TiO2 posredstvom vodenog rastvora. Infiltracija je izvršena u različitim trajanjima, počev od 30 sekundi, 4 minute i 8 minuta. Izvršeno je metalografsko ispitivanje mikrostrukture po dubini, na poprečnom preseku navarenog sloja, kao i ispitivanje otpornosti na habanje kako bi se ustanovio uticaj prisustva infiltriranih nano čestica.

Influence of kinematic factors of friction stir welding on the characteristics of welded joints of forged plates made of EN AW 7049 A aluminium alloy

Original scientific paper In this paper, the influence of rotation speed and welding speed on the impact strength, microstructure and cross section micro hardness of FSW welded joints of Al-Zn-Mg-Cu high strength aluminium alloy is studied. Rotation speed was varied from 750 min to 850 min and welding speed from 60 mm/min to 80 mm/min. It was found that the energy of crack propagation is up to three times higher than the energy of crack initiation. This ratio was found by testing the Charpy notched specimens taken from left and right from the weld centre, 4 mm from the notch in a direction opposite to a direction of welding. Micro hardness distribution in the nugget does not show large dissipation of value regardless if the measuring point is in the upper or lower section of the nugget. Weld microstructure characteristics and zones are clearly defined at the basis of grain size and material flow.