100Cr6 Çeliğinde Kısmi ve Tam Östenitlemede Karbür Çözünmesi Kinetiği

Bu çalışmada, 100Cr6 çeliğinde kısmi ve tam östenitleme koşullarında sementit çözünme kinetiği incelenmiştir. 840 °C ve 1050 °C sıcaklıkta farklı sürelerde ısıl işleme tabi tutulan numunelerde sementit hacim oranındaki ve boyutundaki değişim belirlenmiştir. ImageJ yazılımı ile SEM mikrografları analiz edilerek karbürlerin boyutu ve hacim oranları belirlenmiştir. Elde edilen istatistiksel veriler “lineer olmayan eğri uydurma” yöntemi kullanılarak çözünme eğrilerine dönüştürülmüştür. Tam ve kısmi östenitleme işlemlerinin başlangıcında sementit çözünme hazının yüksek olduğu belirlenmiştir. Bir model kurularak DICTRA yazılımında karbür çözünmesi hesaplanmıştır. Elde edilen çözünme eğrileri DICTRA sonuçları ile karşılaştırılmıştır. SEM mikrograflarından elde edilen istatistikler ile DICTRA hesaplamalarının uyumlu olduğu görülmüştür. Elde edilen hesaplama sonuçlarına göre başlangıçtaki hızlı karbür çözünmesinin nedeni, C atomları difüzyonu ile kontrol edilen ve Cr difüzyonunun ihmal edildiği “ihmal edilebilir yerel denge” modunda çözünmenin gerçekleşmesidir.

Anahtar Kelimeler:

Östenitleme, kinetik simülasyon, çözünme kinetiği, görüntü analizi, ımageJ

Carbide Dissolution Kinetics during Partial and Full Austenitization in 100Cr6 Steel

In this work, cementite dissolution kinetics was studied in 100Cr6 steel during partial and full austenitization. The change in cementite volume fraction and size was determined from samples heat treated for different durations at 840 °C and 1050 °C. The SEM micrographs were analyzed by using ImageJ software to count size and volume fraction of carbides. The obtained statistical data were used to draw the dissolution curves with a nonlinear curve fitting method. It was found that the cementite dissolution rate is fast at the beginning of partial and full austenitization. A model was established and carbide dissolution was calculated using DICTRA software. The dissolution curves were obtained and compared with the DICTRA simulations. The calculation results are in good agreement with the dissolution curves from statistical results of SEM micrographs. According to the calculation results, the fast carbide dissolution is due to dissolution under non-partitioning local equilibrium (NPLE) mode controlled by diffusion of C atoms and neglecting diffusion of Cr.

Keywords:

Austenitization, kinetic simulations, dissolution kinetics, image analysis, imageJ,

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Bhadeshia, H. K. D. H. (2012). Steels for bearings. Progress in materials Science, 57(2), 268-435.Stickels, C. A. (1974). Carbide refining heat treatments for 52100 bearing steel. Metallurgical Transactions, 5(4), 865-874.Xi, Z. J., Koyama, M., Yoshida, Y., Yoshimura, N., Ushioda, K., & Noguchi, H. (2015). Effects of cementite morphology on short-fatigue-crack propagation in binary Fe–C steel. Philosophical Magazine Letters, 95(7), 384-391. Verhoeven, J. D. (2000). A review of microsegregation induced banding phenomena in steels. Journal of materials engineering and performance, 9(3), 286-296. Adishesha, P. K. (2002). Effect of steel making and processing parameters on carbide banding in commercially produced ASTM A-295 52100 bearing steel. In Bearing Steel Technology. ASTM International.Van der Ven, A., & Delaey, L. (1996). Models for precipitate growth during the γ→ α+ γ transformation in Fe-C and Fe-C-M alloys. Progress in materials science, 40(3), 181-264. Zhao, L., Vermolen, F. J., Sietsma, J., & Wauthier, A. (2006). Cementite dissolution at 860 C in an Fe-Cr-C steel. Metallurgical and Materials Transactions A, 37(6), 1841-1850. Epp, J., Surm, H., Kessler, O., & Hirsch, T. (2007). In situ X-ray phase analysis and computer simulation of carbide dissolution of ball bearing steel at different austenitizing temperatures. Acta Materialia, 55(17), 5959-5967.Li, H., Zhang, H., Lv, Z. F., & Zhu, Z. F. (2017). Cementite Dissolution Kinetics of High Carbon Chromium Steel During Intercritical Austenitization. Journal of Phase Equilibria and Diffusion, 38(4), 543-551.Erişir, E., Bilir, O. G., & Gezmişoğlu, A. E. (2017, March). Carbide banding formation and prevention in 52100 bearing steels. In TMS 2017 146th Annual Meeting & Exhibition.Erişir, E., Bilir, O. G., & Gezmişoğlu, A. E. (2017, February). A study of carbide dissolution in bearing steels using computational thermodynamics and kinetics. In IOP Conference Series: Materials Science and Engineering (Vol. 179, No. 1, p. 012021). IOPSchneider, C. A., Rasband, W. S., & Eliceiri, K. W. (2012). NIH Image to ImageJ: 25 years of image analysis. Nature methods, 9(7), 671. Coudert, J. B., Mondelin, A., Alglave, J. L., Carrerot, H., & Maheo, Y. (2017). Assessment of Advanced Aerospace Bearing Steel RCF Performances Using a Discriminating Multicontact Test. In Bearing Steel Technologies: 11th Volume, Advances in Steel Technol. Andersson, J. O., Helander, T., Höglund, L., Shi, P., & Sundman, B. (2002). Thermo-Calc & DICTRA, computational tools for materials science. Calphad, 26(2), 273-312.Zhang, G. H., Chae, J. Y., Kim, K. H., & Suh, D. W. (2013). Effects of Mn, Si and Cr addition on the dissolution and coarsening of pearlitic cementite during intercritical austenitization in Fe-1mass% C alloy. Materials characterization, 81, 56-67.Krishna, S. C., Tharian, K. T., Chakravarthi, K. V. A., Jha, A. K., & Pant, B. (2016). Heat treatment and thermo-mechanical treatment to modify carbide banding in AISI 440C steel: a case study. Metallography, Microstructure, and Analysis, 5(2), 108-115.Barrow, A. T. W., Kang, J. H., & Rivera-Díaz-del-Castillo, P. E. J. (2012). The ϵ→ η→ θ transition in 100Cr6 and its effect on mechanical properties. Acta materialia, 60(6-7), 2805-2815.