Yazar "Altinay, Yasemin" seçeneğine göre listele

Listeleniyor 1 - 7 / 7
  • Küçük Resim
    Öğe
    Determination of fracture toughness of boride layers grown on Co1.21Cr1.82Fe1.44Mn1.32Ni1.12Al0.08B0.01 high entropy alloy by nanoindentation
    (Elsevier Sci Ltd, 2022) Gunen, Ali; Makuch, Natalia; Altinay, Yasemin; Carboga, Cemal; Dal, Serkan; Karaca, Yusuf
    Multiphase boride layers consisting of (CoFe)2B, (Fe0.4Mn0.6)B, Cr2Ni3B6 and (Cr0.4Mn0.6)B were formed on the surface of Co1.21Cr1.82Fe1.44Mn1.32Ni1.12Al0.08B0.01 high entropy alloy by powder-pack boronizing at 900 degrees C, 950 degrees C and 1000 degrees C for 4 h. The nanohardness (H), modulus of elasticity (E) and fracture toughness (KC) of the multiphase boride layers were determined based on the load-displacement (P-h) curves obtained in the nanoindentation tests. Three distinct regions were identified on the cross-sections of the produced layers: an outer layer consisting of MeB-type borides, an inner layer consisting of Me2B-type borides and the transition zone. The microstructural aspects of the layers were investigated using scanning electron microscopy, energy-dispersive Xray spectroscopy, and X-ray diffraction. Detailed analysis of the influence of the chemical composition on hardness, elastic modulus and fracture toughness in the three regions indicated that the most critical factor influencing the mechanical properties was the presence of chromium, iron and cobalt borides in the microstructure. Especially the formation of chromium borides reduced the fracture toughness of the transition zone.
  • Küçük Resim
    Öğe
    Effect of powder-pack aluminizing on microstructure and oxidation resistance of wire arc additively manufactured stainless steels
    (Elsevier Science Sa, 2023) Gurol, Ugur; Altinay, Yasemin; Gunen, Ali; Bolukbasi, Omer Saltuk; Kocak, Mustafa; Cam, Gurel
    This study investigated the effect of powder-pack aluminizing treatment on the high-temperature oxidation of ER307 stainless steel components fabricated by wire arc additive manufacturing (WAAM) during isothermal oxidation at 1000 degrees C for 5 h, 25 h, and 50 h. Scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), X-Ray fluorescence (XRF), nanoindentation testing, and oxidation testing were used to characterize the aluminized and non-aluminized samples produced by WAAM. The results showed that the powder-pack aluminizing increased the surface nano-hardness up to 13.95 GPa and the modulus of elasticity up to 159 GPa, as well as improving the microstructure of WAAM ER307 stainless steel. Indeed, aluminide coatings remained stable up to temperatures exceeding 1000 degrees C, and the growth of hematite, the main oxide phase, was inhibited by a preferential alumina growth (Al2O3), resulting in an improvement in oxidation resistance in the range of 46-70 %. In addition, owing to the advantages of low-temperature aluminizing, the microstructure, mechanical properties, and oxidation resistance of these alloys have been improved without causing sigma phase formations, which constitute a significant problem in high-temperature heat treatment of stainless steels.
  • Küçük Resim
    Öğe
    Effect of the incorporating of refractory NbC precipitates in intermetallic iron-aluminide coatings on corrosion and high-temperature oxidation behavior
    (Elsevier Science Sa, 2024) Gunen, Ali; Altinay, Yasemin; Sabun, Sahin; Alkan, Sabri
    This study aims to investigate the effects of growing niobium carbide (NbC) particles into intermetallic iron-aluminide (FeAl) coatings on ductile cast iron (SGI) by thermo-reactive diffusion technique (TRD). The study compares the corrosion and oxidation behavior of the FeAl-NbC coatings with SGI, FeAl, and NbC coatings. Corrosion tests were conducted through polarization tests in a 3.5 wt% NaCl solution, while oxidation tests were performed at 900 degrees C for 4, 16, and 64 h. Before and after corrosion and oxidation tests, the coatings were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The findings show that FeAl coatings with NbC particles had lower graphite nodules, porosity, and surface roughness values compared to FeAl coatings. FeAl-NbC composite coatings provided better corrosion and oxidation resistance compared to untreated SGI, FeAl, and NbC coatings. The results of the comparative analysis of FeAl-NbC, FeAl, NbC, and untreated SGI specimens indicate that corrosion resistance in a 3.5 wt% NaCl solution and oxidation resistance at 900 degrees C followed the order FeAl-NbC > FeAl > NbC > SGI.
  • Küçük Resim
    Öğe
    Investigation of Multi-Phase Structure and Optoelectronic Performance of Bi-Doped (Cu-Zn) Oxide Composite Thin Films
    (Wiley-V C H Verlag Gmbh, 2023) Altinay, Yasemin; Akkaya, Abdullah; Aydin, Rasit; Sahin, Bunyamin
    In this research, thin film composite structures were used to prepare optoelectronic devices from bare and Bi-substituted p-CuO/n-ZnO systems. The p-CuO/n-ZnO composite thin film structures were prepared by the SILAR technique, and the influences of two different Bi contents on the structure and main physical performances of the samples were investigated. The X-ray diffraction (XRD) technique showed that the composited thin film materials were multiphased in rutile hexagonal (wurtzite) phase (ZnO) and monoclinic tenorite phase (CuO) type crystal structure. The obtained surface morphological results presented that the structure exhibits an almost homogeneous, plate-like surface distribution, and depending on the increase of Bi concentration, the plate-like sheet area widens from similar to 2.5 mu m to 10 mu m and the layer boundaries decrease. FT-IR and Raman spectroscopy were used to investigate the various vibration and Raman active phonon modes of Bi:p-CuO/n-ZnO nanostructured heterostructures. For a comprehensive analysis of the optical bandgap of the fabricated composite samples, the estimated values were obtained from the Tauc plot. Produced samples exhibited an Ohmic behavior and dc resistivity values of films can be determined via Ohm's Law. The adjusted sheet resistance value of 11.51 M Omega/sq when the content of Bi 3.0 % in the growth bath.
  • Küçük Resim
    Öğe
    Microstructural characterization and high-temperature wear behavior of refractory niobium-carbide growth in intermetallic iron-aluminide coatings
    (Pergamon-Elsevier Science Ltd, 2024) Gunen, Ali; Altinay, Yasemin; Sabun, Sahin
    Iron-aluminide (Fe-Al) intermetallics are characterized by their high-temperature oxidation resistance. However, their use in tribo-corrosive environments is limited due to their low hardness and brittle nature. To overcome this weakness, the feasibility of forming composite coatings (NbC-FeAl) by intercalation of refractory NbC particles into Fe-Al coatings by thermo-reactive diffusion technique and its effect on high-temperature wear behavior was investigated in this study. The coatings obtained underwent comprehensive characterization using scanning electron microscopy, X-ray diffraction, microhardness measurements, and ball-on-disc wear tests, providing valuable insights into their properties. The characterization studies showed that increasing the growth of NbC in the intermetallic iron-aluminide content resulted in a slight increase in the hardness and a decrease in the thickness of the iron-aluminide layer. Moreover, the formation of NbC in Fe-Al coatings increased the dislocation densities of the coatings, resulting in an improvement of wear resistance 2.7 times at room temperature and up to 3.5 times at 500 degrees C. While different wear mechanisms occurred in coated samples at room temperature, the dominant wear mechanism at 500 degrees C evolved into an oxidatively supported adhesive wear mechanism. This study showed that Fe-Al coatings exhibited better wear response at both room and elevated temperatures when reinforced with NbC.
  • Küçük Resim
    Öğe
    Microstructure, hardness and high temperature wear characteristics of boronized Monel 400
    (Elsevier Science Sa, 2022) Kucuk, Yilmaz; Doleker, K. Mert; Gok, M. Sabri; Dal, Serkan; Altinay, Yasemin; Erdogan, Azmi
    Boronizing processes were carried out at 900 degrees C, 950 degrees C and 1000 degrees C for 2, 4 and 6 h to improve the wear performance of Monel 400 alloy. According to microstructure analyses and nanoindentation tests, Ni2B, FeNiB and FeB phases were detected as dominant phases in the boronized layer. Apart from this, it was observed that the amount of Cu deposits in the boronized layers increased depending on the increasing boronizing temperature. After the boronizing process, the boride layer thickness and hardness values were found to be in the range of 32-272 mu m and 12.76-17.83 GPa, respectively. From the results of dry sliding wear test, the wear volume loss values of the boronized Monel 400 alloy decreased by approximately 25 times compared to the untreated samples. The lowest volume loss value among all test samples was observed in the boronized sample at 950 degrees C for 4 h. In addition to the hardness value, it was determined that the morphology and mechanical properties of the boronized layer were also effective on the wear results. Plastic deformation, delamination and oxidation type wear mechanisms were observed as the dominant wear mechanisms in the room and high temperature tests of boronized samples.
  • Küçük Resim
    Öğe
    Microstructure, some mechanical properties and tribocorrosion wear behavior of boronized Al0.07Co1.26Cr1.80Fe1.42Mn1.35Ni1.10 high entropy alloy
    (Elsevier Science Sa, 2021) Karakas, Mustafa Serdar; Gunen, Ali; Carboga, Cemal; Karaca, Yusuf; Demir, Mehmet; Altinay, Yasemin; Erdogan, Azmi
    High-entropy alloys (HEAs) with face-centered cubic (FCC) structures exhibit high toughness and corrosion resistance, but their average strengths and relatively low wear resistance can limit their engineering ap-plications. In this study, FCC Al0.07Co1.26Cr1.80Fe1.42Mn1.35Ni1.10 HEAs were boronized for 4 h at temperatures of 900, 950, and 1000 degrees C to form hard, protective metal borides on their surfaces. The microstructural characteristics of the borides formed were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mechanical properties of the boride layers were studied by nanoindentation measurements, and the tribological performances of the layers were evaluated by ball-on -disk type wear tests in air, 3.5% NaCl and 5% H2SO4. Irrespective of the boronizing temperature, (Fe0.4Mn0.6) B, (Cr0.4Mn0.6)B, (CoFe)B2 and Cr2Ni3B6 phases were detected in the surfaces of the boronized samples. The surface hardnesses of the boronized samples reached nearly ten times the hardness of the as-cast HEA. The borides were effective in reducing friction as well as wear. Increasing the boronizing temperature increased the thicknesses of the coatings and further improved wear characteristics. Wear rates in 5% H2SO4 were generally higher than the wear rates in 3.5% NaCl, but the highest wear rates were observed in air. (c) 2021 Elsevier B.V. All rights reserved.