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Article Citation - WoS: 10Citation - Scopus: 20A Comparison of the Ballistic Performances of Various Microstructures in Mil-A Armor Steel(Mdpi, 2020) Konca, ErkanDue to their advantageous properties, there is a growing interest in developing armor steels containing fully or partially bainitic microstructures. In this study, bainitic and martensitic microstructures were obtained in rolled homogeneous armor (RHA) steel samples and their ballistic protection performances were investigated. RHA (MIL-A-12560) steel samples were subjected to isothermal heat treatments at three different temperatures, where one temperature (360 degrees C) was above the martensite formation start (Ms) temperature of 336 degrees C while the other two (320 degrees C and 270 degrees C) were below. For the assessment of the ballistic protection performance, the kinetic energy losses of the 12.7 mm bullets fired at the test samples were determined. The promising nature of the bainite microstructure was confirmed as the sample isothermally treated at 360 degrees C provided approximately 10% higher ballistic protection as compared to the regular RHA sample of tempered martensite microstructure. However, the ballistic performances of the isothermally treated samples decreased as the treatment temperature went below the Ms temperature. Following the ballistic tests, hardness measurements, impact tests at -40 degrees C, and macro- and microstructural examinations of the samples were performed. No correlation was found between the hardness and impact energies of the samples and their ballistic performances.Article Effect of Aluminizing on the Oxidation of Inconel 718 and Inconel 738LC Superalloys at 925-1050 °C(MDPI, 2025) Telbakiroglu, Yusuf Burak; Konca, ErkanThis study was undertaken to investigate the effect of aluminizing on the oxidation of Inconel 718 and Inconel 738LC superalloys. Bare and high-activity chemical vapor deposition (CVD) aluminized Inconel 718 and Inconel 738LC samples were oxidized in air at 925, 1000, and 1050 degrees C for 200 h. Detailed cross-sectional examinations, elemental analyses, mass change measurements, and X-ray diffraction studies were performed. It was observed that the oxidation resistances of both alloys were significantly improved by the Al2O3 scale formed on the NiAl layer that was created on the surfaces of the samples during aluminizing. The beneficial effect of aluminizing was found to be more evident in the case of Inconel 738LC alloy samples which showed lower oxidation rates at all test temperatures. The results have been discussed on the basis of the differences in aluminum contents of the alloys and their effects on diffusion.Article Citation - WoS: 24Effects of Current Density, Coating Thickness, Temperature, Ph and Particle Concentration on Internal Stress During Ni-mos2 Electrocodeposition(Taylor & Francis Ltd, 2014) Guler, E. Saraloglu; Karakaya, Ishak; Konca, ErkanInternal stress in plated deposits has been a common problem that may affect the functionality of coatings. Electrodeposition parameters and insoluble particles modify the characteristics and the level of internal stress of coatings. The influence of the electrocodeposition parameters and their interaction effects on the internal stress during the electrodeposition of Ni and Ni-MoS2 composite coatings were studied by fractional factorial design. The parameters studied and their ranges were: MoS2 particle concentration (0-10 g L-1), temperature (30-50 degrees C), pH (2-4), current density (1.2-4.8 A dm(-2)), and coating thickness (25-50 mu m). MoS2 addition into Watts bath resulted in the decrease in the tensile internal stress values or even changed the stress character from tensile to compressive. Moreover, low stress values were obtained when pH was 2 and coating thickness was 50 mu m.Article Citation - WoS: 29Citation - Scopus: 34Effects of Alloying Elements (Mo, Ni, and Cu) on the Austemperability of GGG-60 Ductile Cast Iron(Mdpi, 2017) Konca, Erkan; Tur, Kazim; Koc, ErkinThe interest in austempered ductile irons (ADI) is continuously increasing due to their various advantageous properties over conventional ductile irons and some steels. This study aimed to determine the roles of alloying elements Ni, Cu, and Mo, on the austemperability of GGG-60 ductile cast iron. Two different sets of GGG-60 (EN-GJS-600-3) samples, one set alloyed with Ni and Cu and the other set alloyed with Mo, Ni, and Cu, were subjected to austempering treatments at 290 degrees C, 320 degrees C, and 350 degrees C. A custom design heat treatment setup, consisting of two units with the top unit (furnace) serving for austenitizing and the 200 L capacity bottom unit (stirred NaNO2-KNO3 salt bath) serving for isothermal treatment, was used for the experiments. It was found that austempering treatment at 290 degrees C increased the hardness of the Ni-Cu alloyed GGG-60 sample by about 44% without causing a loss in its ductility. In the case of the Mo-Ni-Cu alloyed sample, the increase in hardness due to austempering reached to almost 80% at the same temperature while some ductility was lost. Here, the microstructural investigation and mechanical testing results of the austempered samples are presented and the role of alloying elements (Mo, Ni, and Cu) on the austemperability of GGG-60 is discussed.
