34CrNiMo6 Malzemesine Uygulanan Sıcak Şekillendirme İşleminin Dislokasyon Yoğunluğuna Etkisi

Abstract

Bu çalışmada ticari olarak satın alınan 34CrNiMo6 malzemesi diğer adıyla 4340 çeliği sıcak dövme ile şekillendirilmiştir. Dövme işleminden önce ve sonra metalografik işlemler için kesilen numunelerin mikroyapıda oluşan farklılıkları taramalı elektron mikroskobu (SEM) ile gözlemlenmiştir. Oluşan farklı bölgelerdeki element oranları, enerji dağıtıcı X-ışını spektrometrisi (EDS) ile analiz edilmiştir. Malzamelerde ki dislokasyon yoğunluğunu ve kristalite boyutunu bulabilmek için X-Işını Kırınım (XRD) analizi yapılmıştır. XRD analiziyle dövme işleminin malzemede oluşturduğu kafes gerinimi de hesaplanarak ana malzemeyle karşılaştırılmıştır. Dövme işleminin malzemede oluşturduğu mekanik etkiler incelenip dinamik yeniden kristalleşmenin oluşmasıyla malzemede ki değişimler araştırılmıştır. Dinamik yeniden kristalleşme ile dislokasyon yoğunluğu arasındaki ilişki gösterilmiştir. Aynı zamanda mikro sertlik değerleri HV0.5 göre ölçülüp dislokasyon yoğunluğu ile ilişkisi incelenmiştir. Yapılan analizler sonucu ana malzemenin dislokasyon yoğunluğu dövme işlemi sonrası ortalama %50 azalmış, kristalite boyutu ise ortalama %20 artmıştır. Dövme işlemi sonrası malzemede kafes gerinim değerinin yaklaşık %30 azaldığı gözlemlenmiştir. Bu değerlerin değişimi ile sertlik değerleri arasındaki ilişki araştırılmıştır. En yüksek sertlik ana malzemede ölçülmüştür.

Keywords

• 34CrNiMo6
• Dövme
• Dislokasyon yoğunluğu

Effect of Hot Forming Process on 34CrNiMo6 Material on Dislocation Density

Abstract

In this study, commercially purchased 34CrNiMo6 material, also known as 4340 steel, was shaped by hot forging. The microstructure differences of the samples cut for metallographic processes before and after forging were observed by scanning electron microscope (SEM). Element ratios in the different regions formed were analyzed by energy dispersive X-ray spectrometry (EDS). X-Ray Diffraction (XRD) analysis was performed to find the dislocation density and crystallinity size in the materials. With XRD analysis, the lattice strain created by the forging process in the material was also calculated and compared with the raw material. The mechanical effects of the forging process on the material were examined and the changes in the material with the formation of dynamic recrystallization were investigated. The relationship between dynamic recrystallization and dislocation density is shown. At the same time, the microhardness values were measured according to HV0.5 and the relationship with the dislocation density was examined. As a result of the analysis, the dislocation density of the raw material decreased by 50% on average after forging, and the crystallite size increased by 20% on average. It was observed that the lattice strain value of the material decreased by about 30% after forging. . The relationship between the change of these values and the hardness values was investigated. The highest hardness was measured in the base material.

Keywords

• 34CrNiMo6
• Forging
• Dislocation density

References

1. [1] Altuntaş, G., Altuntaş, O., Öztürk, M. K., & Bostan, B. (2022). Metallurgical and Crystallographic Analysis of Different Amounts of Deformation Applied to Hadfield Steel. International Journal of Metalcasting, 1-10.
2. [2] Güral, A. H. M. E. T., & Altuntaş, O. N. U. R. (2021). Improving the impact toughness properties of high carbon powder metallurgy steels with novel spherical cementite in the bainitic matrix (SCBM) microstructures. Materials Chemistry and Physics, 259, 124203.
3. [3] Belyaev, A. K., Polyanskiy, A. M., Polyanskiy, V. A., Sommitsch, C., & Yakovlev, Y. A. (2016). Multichannel diffusion vs TDS model on example of energy spectra of bound hydrogen in 34CrNiMo6 steel after a typical heat treatment. International journal of hydrogen energy, 41(20), 8627-8634.
4. [4] Maropoulos, S., Ridley, N., & Karagiannis, S. (2004). Structural variations in heat treated low alloy steel forgings. Materials Science and Engineering: A, 380(1-2), 79-92.
5. [5] Kuduzović, A., Poletti, M. C., Sommitsch, C., Domankova, M., Mitsche, S., & Kienreich, R. (2014). Investigations into the delayed fracture susceptibility of 34CrNiMo6 steel, and the opportunities for its application in ultra-high-strength bolts and fasteners. Materials Science and Engineering: A, 590, 66-73.
6. [6] Hebsur, M. G. (1982). Recent attempts of improving the mechanical properties of AISI 4340 steel by control of microstructure—A brief review. Journal of materials for energy systems, 4(1), 28-37.
7. [7] Safi, S. M., & Givi, M. K. B. (2014). A new step heat treatment for steel AISI 4340. Metal Science and Heat Treatment, 56(1), 78-80.
8. [8] Araujo Barros, R., Abdalla, A. J., Rodrigues, H. L., & dos Santos Pereira, M. (2014). Characterization of a AISI/SAE 4340 steel in different microstructural conditions. In Materials Science Forum (Vol. 775, pp. 136-140). Trans Tech Publications Ltd.

9. [9] Meng, Q., La, P., Yao, L., Zhang, P., Wei, Y., & Guo, X. (2016). Effect of Al on microstructure and properties of hot-rolled 2205 dual stainless steel. Advances in Materials Science and Engineering, 2016.
10. [10] Capdevila, C., FG, C., & De Andrés, C. G. (2002). Determination of Ms temperature in steels: A Bayesian neural network model. ISIJ international, 42(8), 894-902.
11. [11] Hwang, K. C., Lee, S., & Lee, H. C. (1998). Effects of alloying elements on microstructure and fracture properties of cast high speed steel rolls: Part I: Microstructural analysis. Materials Science and Engineering: A, 254(1-2), 282-295.
12. [12] Toji, Y., Matsuda, H., & Raabe, D. (2016). Effect of Si on the acceleration of bainite transformation by pre-existing martensite. Acta Materialia, 116, 250-262.
13. [13] Speer, J. G., Edmonds, D. V., Rizzo, F. C., & Matlock, D. K. (2004). Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation. Current Opinion in Solid State and Materials Science, 8(3-4), 219-237.
14. [14] Matsumura, O., Sakuma, Y., & Takechi, H. (1987). Enhancement of elongation by retained austenite in intercritical annealed 0.4 C-1.5 Si-O. 8Mn Steel. Transactions of the Iron and Steel Institute of Japan, 27(7), 570-579.
15. [15] Łukaszek-Sołek, A., Krawczyk, J., Śleboda, T., & Grelowski, J. (2019). Optimization of the hot forging parameters for 4340 steel by processing maps. Journal of Materials Research and Technology, 8(3), 3281-3290.
16. [16] Scherrer, P. (1912). Bestimmung der inneren Struktur und der Größe von Kolloidteilchen mittels Röntgenstrahlen. In Kolloidchemie Ein Lehrbuch (pp. 387-409). Springer, Berlin, Heidelberg.
17. [17] Totten, G. E. (2006). Steel Heat Treatment Handbook-2 Volume Set. CRC press.
18. [18] Askeland, D. R., & Wright, W. J. (2018). Essentials of materials science and engineering. Cengage Learning.
19. [19] Kayalı, S., & Çimenoğlu, H. (1995). Plastik şekil verme ilke ve uygulamaları. Bilim Teknik Yayınevi, İstanbul, 1, 61.
20. [20] Callister, W. D., & Rethwisch, D. G. (2000). Fundamentals of materials science and engineering (Vol. 471660817). London: Wiley.
21. [21] Miyata, K., Kushida, T., Omura, T., & Komizo, Y. (2003). Coarsening kinetics of multicomponent MC-type carbides in high-strength low-alloy steels. Metallurgical and Materials Transactions A, 34(8), 1565-1573.
22. [22] Lee, B. J. (1992). On the stability of Cr carbides. Calphad, 16(2), 121-149.
23. [23] Ion, S. E., Humphreys, F. J., & White, S. H. (1982). Dynamic recrystallisation and the development of microstructure during the high temperature deformation of magnesium. Acta Metallurgica, 30(10), 1909-1919.