Browsing by Author "Hocalar Ç."

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    Characterization of hot forged P285NH steel by metallurgical investigation and reliability analysis; [Charakterisierung von warmgeschmiedetem P285NH-Stahl durch metallurgische Untersuchungen und Zuverlässigkeitsanalyse]
    (Wiley-VCH Verlag, 2020) Saklakoğlu N.; Çivi C.; Hocalar Ç.; Demirok S.
    An extensive study was carried out to investigate the effect of cooling rate after hot forging process and normalization step on the hardness, strength and impact toughness and microstructure of P285NH steel. Understanding of the combined effect of cooling rate and normalization on the mechanical and microstructural properties of the steel would help to select conditions required to achieve optimum mechanical properties. The results indicated that the microstructures of all forging and cooling conditions were dominated by ferrite and pearlite phases with different morphologies and grain sizes according to various cooling rates. Conveyor cooling led to a formation of relatively fine acicular ferrite and pearlite grains in comparison to batch cooling which presented coarse polygonal ferrite with pearlite. Based on the data fluctuation of Charpy tests, the normal distribution provided a statistical analysis method for assessing the reliability. Through the statistical analysis of the distribution function, it can be concluded that normalization step is necessary for higher reliability. Both batch cooling and conveyor cooling did not give the required reliability level for safety components due to heterogeneities in the microstructure. © 2020 Wiley-VCH GmbH
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    The Effect of Heat Treatment on The Wear and Corrosion Behavior of AISI 440B Martensitic Stainless Steel in Different Environments
    (Springer, 2025) Saklakoğlu N.; Eyici G.; Aslan N.; Hocalar Ç.; Çimen O.
    This study demonstrates that the austenitization temperature of AISI 440B martensitic stainless steel crucially influences wear and corrosion resistance. As the austenitization temperature increases, Cr23C6 carbides dissolve, leading to increased Cr and C concentrations in the austenite matrix. Higher Cr content enhances corrosion resistance, while increased C content raises hardness. However, excessively high austenitization temperatures result in increased retained austenite due to lowered Mf temperatures and grain coarsening, which significantly reduces hardness. Electrochemical corrosion tests that have been done in wet wipe solution and NaCl solution have shown that a high carbon content can break the martensitic crystal lattice, destabilizing the protective oxide film and reducing corrosion resistance. This study identifies 1110 °C as the optimal austenitization temperature for AISI 440B martensitic stainless steel, balancing both wear and corrosion resistance effectively. © The Indian Institute of Metals - IIM 2025.