Adnan Akkurt

Comparison of Burnishing Process with Other Methods of Hole Surface Finishing Processes Applied on Brass Materials

In this article, effects of traditional surface machining processes and a newly used surface finishing process called burnishing process on a brass material are compared on the basis of microstructure, circularity, cylindricity, and surface roughness. For this reason, test samples made of brass material which is a non-ferrous metal were prepared to be widely used in many fields of machining industry as it accurately reveals deformation effects of surface finishing processes, and those samples were subjected to drilling, lathing, reaming, grinding, honing, and burnishing. After these processes, hole surface roughness, cylindricity, and change in microstructure were analyzed. All surface machining processes were performed under constant depth of cut, cutting speed, and feed rate. Data collected after experimental research indicates that the best combination of surface characteristics is obtained by burnishing process, in comparison to all other different methods of finishing. Also the highest hardness and best surface quality of machined surface are provided with burnishing. All results show that burnishing should be preferred to provide the optimum characteristics in hole surfaces subjected to continuous deformation and corrosion.

Mechanochemical synthesis and characterization of pure Co2B nanocrystals

Cobalt boride (Co2B) is a significant transition metal boride having a wide range of usage area due to its high oxidation, abrasion and corrosion resistance as well as its superior electrochemical, magnetic and anisotropic properties. In this study, pure Co2B nanocrystals were synthesized with Co, B2O3 and Mg as starting materials via the mechanochemical synthesis (MCS) method by high-energy planetary ball mill in a hardened steel vial with hardened steel balls. All the experiments were conducted under Ar atmosphere at different rotational speeds and at 20 : 1–30 : 1–40 : 1 ball-to-powder ratios. Leaching of Co2B + MgO powder mixtures occurred after milling and purified with acetic acid and pure Co2B nanocrystals were obtained in solid form. The Co2Bs were characterized through X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, Brunauer–Emmett–Teller and specific density analyses, and effects of synthesis parameters on product properties were revealed. Surface areas of the powders synthesized at 40 : 1 ball-to-powder ratio at different rotational speeds were measured as 21.14, 40.36 and 52.33 m2 g−1, respectively. Crystallite sizes of Co2B nanocrystals were between 7.27 and 9.84 nm and their specific density varied between 7.61 and 7.78 g cm−3. It was determined that all samples were saturated and exhibited hysteresis and ferromagnetic behaviours, and saturation magnetization was between 35 and 50 emu g−1.

Mathematical Modeling of Diameter and Circularity Deviation in Wire Electrical Discharge Machining of a Hot Work Tool Steel

Abstract The suitable selection of manufacturing process and conditions are very important in manufacturing processes to obtain good surface quality and dimensional precision. Thus, it is required to know properties relating to material, surface quality and dimensional precision by means of mathematical models which allow some predictions taking into account operation conditions such as feed rate, current and pulse on time, etc. Wire electrical discharge machining (WEDM) represents a modification of electro discharge machining (EDM) and is widely used for a long time for cutting punches and dies, shaped pockets as well as other machine parts on conductive work materials. Present work is focused on the regression modeling predicting diameter and circularity deviation of a hot work tool steel. Mathematical relationships between circularity and diameter deviation as well as WEDM cutting parameters (feed rate, current and pulse on time) have been investigated. Results show that, regression analysis can be successfully applied for this mathematical model.

Laser surface treatment of S235JRC carbon steel with Co2B nanocrystals

Abstract In this study, Co2B nanocrystals, which were synthesized in a planetary type mill by using the mechanochemical method, were pre-coated on the surface of S235JRC low carbon steel substrates, and then the surfaces were clad using a CO2 laser. In the experiments, laser scan speed was kept constant and laser power was specified as the variable parameter. The microstructure and phases of the coatings were investigated by using X-ray diffractometry, scanning electron microscopy, and optical microscopy. The mechanical properties of the coatings were characterized using micro-hardness, ball-on-disc wear, and scratch testing. The thickness of the coatings depending on the laser power was measured in the range 35–71 μm. The hardness and the wear resistance of the coatings were approximately 3 times higher compared to the base metal due to FeN0.0760, Fe15.1C, FeCo, and B2C5N2 phases of the coatings. The most durable coatings against wear were obtained at 174 W and 220 W laser powers.

Improving the surface topography of mild steel with the burnishing process

Abstract The effects of burnishing and other conventional machining processes (grinding, reaming, drilling, turning, and honing) on the surface characteristic properties of mild steel were investigated and compared in terms of surface roughness, circularity (roundness), and cylindricity in this study. The effect of these processes on the microstructures was also examined to understand the relationship between the machining process and surface characteristic properties. All surface machining processes were performed under constant depth of cut, cutting speed, and feed rate. The highest hardness was obtained on the burnished surface. Experimental results also showed that the roller burnishing method is the most favorable post-machining process method for obtaining optimum surface topography on mild steel.