محاسبه ضرایب نفوذ عناصر در اثر عملیات همگن سازی سوپرآلیاژ اینکونل 718 ریختگی

نوع مقاله: مقاله کامل علمی پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، دانشکده مهندسی متالورژی و مواد، دانشکده فنی، دانشگاه تهران

2 دانشیار، دانشکده مهندسی متالورژی و مواد، دانشکده فنی، دانشگاه تهران

10.22034/frj.2019.198934.1098

چکیده

‏از آنجا که مطالعه نفوذ عناصر آلیاژی در نیکل به طور کلی بر مبنای زوج های نفوذی است و حضور عناصر دیگر در سوپرآلیاژ بر نفوذ هر عنصری ‏تاثیرگذار است، نیاز به روش محاسباتی است که توسط آن بتوان ضرایب نفوذ را به شکل مستقیم در سوپرآلیاژ محاسبه کرد. در تحقیق حاضر، ریزساختار ‏ریختگی سوپرآلیاژ اینکونل 718 بررسی شد و مشخص شد که این ریزساختار شامل دندریت های آستنبیت است که عناصر نیوبیم، مولیبدن، و تیتانیم را به مناطق ‏بین دندریتی پس زده‌اند. همچنین ساختار یوتکتیک فاز لاوه/آستنیت و فازهای ‏NbC‏ و ‏TiN‏ در این مناطق شناسایی شدند. در ادامه، ریزجدایش عناصر نیوبیم، ‏مولیبدن و تیتانیم در این سوپرآلیاژ و کاهش اثرات آن در حین عملیات حرارتی همگنسازی مورد بررسی قرارگرفت. بر اساس مفهوم شاخص جدایش باقیمانده، در ‏طی عملیات همگنسازی، ضرایب نفوذ و انرژی فعال‌سازی برای نفوذ این عناصر در زمینه آستنیتی سوپرآلیاژ به دست آمد. انرژی فعال‌سازی برای نفوذ ‏Nb،Mo ‏ و ‏Ti‏ به ترتیب 232، 286 و 256 کیلوژول بر مول تعیین شد. نتیجه این محاسبات، برای بررسی واکنشهای رسوبگذاری، خزش دمای‏بالا و  ‏فرآیندهای ترمومکانیکی سوپرآلیاژها لازم است.‏

کلیدواژه‌ها


عنوان مقاله [English]

Calculating the Elemental Diffusivities During Homogenization of as-cast Inconel 718 Superalloy

نویسندگان [English]

  • Mohammad Javad Sohrabi 1
  • Hamed Mirzadeh 2
1 M.Sc. Student, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran
2 Associate Professor, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran
چکیده [English]

Since the diffusion of alloying elements in nickel has been studied based on the diffusion couples and the presence of other alloying elements can alter the diffusion of a given element, there is need for a method for direct calculation of the diffusivities form the superalloys. In the present work, the as-cast microstructure of Inconel 718 superalloy was studied, where this microstructure was composed of austenitic dendrites that rejected alloying elements such as Nb, Mo, and Ti to the interdendritic regions. Moreover, the Laves phase/austenite eutectic structure and NbC and TiC phases were characterized in the interdendritic regions. Subsequently, the microsegregation of Nb, Mo, and Ti in the as-cast ingot and its amendment during homogenization heat treatment was studied. Based on the concept of residual segregation index, during homogenization treatment, the diffusivities and the corresponding activation energies for diffusion of these elements in the austenitic matrix were obtained. The activation energy for the interdiffusion of Nb, Mo, and Ti was determined as 232, 286, and 256 kJ/mol, respectively. The outcome of these calculations is important for the precipitation reactions, high-temperature creep, and thermomechanical processing of superalloys.

کلیدواژه‌ها [English]

  • Superalloys
  • Residual segregation index
  • diffusivity
  • activation energy
[1] Anderson M., Thielin A.L., Bridier F., Bocher P., Savoie J., δ phase precipitation in inconel 718 and associated mechanical properties, Materials Science and Engineering A, 2017, 679, 3409-3417.

[2] Alam T., Chaturvedi M., Ringer S.P., Cairney J.M., Precipitation and clustering in the early stages of ageing in Inconel 718, Materials Science and Engineering A, 2010, 527, 7770-7774.

[3] Kañetas P.P., Özturk U., Calvo J., Cabrera J.M., Mata M.G., High-temperature deformation of delta-processed Inconel 718, Journal of Materials Processing Technology, 2018, 255, 204-211.

[4] He D.G., Lin Y.C., et al., Influences of pre-precipitated δ phase on microstructures and hot compressive deformation features of a nickel-based superalloy, Vacuum, 2019, 161, 242-250.

[5] Donachie M., Donachie S., Superalloys a Technical Guide, second ed., ASM International, 2002.

[6]Miao Z.J., Shan A.D., et al., Quantitative analysis of homogenization treatment of INCONEL718 superalloy, Transaction of Nonferrous Metals Society of China, 2011, 21, 1009-1017.

[7] Chen Y., Guo Y., et al., Study on the element segregation and Laves phase formation in the laser metal deposited IN718 superalloy by flat top laser and Gaussian distribution laser, Materials Science and Engineering A, 2019, 754, 339–347.

[8] Patil R.V., Kale G.B., Chemical diffusion of niobium in nickel, Journal of Nuclear Materials, 1996, 230, 57-60.

[9] Karunaratne M., Reed R.C., Interdiffusion of niobium and molybdenum in nickel between 900-1300°C, Defect and Diffusion Forum, 2005, 237, 420-425.

[10] Ugaste Y., Pimenov V.N., Mutual diffusion in the nickel-molybdenum and palladium-molybdenum systems, Fiz. Metal. Metalloved, 1972, 33(5), 1034-1039.

[11] Jung S.B., Yamane T., Minamino Y., Hirao K., Araki H., Saji S., Interdiffusion and its size effect in nickel solid solutions of Ni-Co, Ni-Cr and Ni-Ti systems, Journal of Materials Science Letters, 1992, 11, 1333-1337.

[12]Kramb R.C., Antony M.M., Semiatin S.L., Homogenization of a nickel-base superalloy ingot material, Scripta Materialia, 2006, 54(9), 1645-1649.

[13] Sohrabi M.J., Mirzadeh H., Revisiting the diffusion of niobium in an as-cast nickel-based superalloy during annealing at elevated temperatures, Metals and Materials International, 2019, in press.

[14] Porter D.A., Easterling K.E., Sherif M.Y., Phase transformations in metals and alloys, 3rd ed., CRC Press, Boca Raton, FL, 2009.

[15] Semiatin S.L., Kramb R.C., Turner R.E., Zhang F., Antony M.M., Analysis of the homogenization of a nickel-base superalloy Scripta Materialia, 2004,51(6), 491-495.

[16] Antonov S., Chen W., et al., The effect of phosphorus on the formation of grain boundary laves phase in high-refractory content Ni-based superalloys. Scripta Materialia. 2019, 161, 44-48.

[17] Ritter N.C., Sowa R., et al., Effects of solid solution strengthening elements Mo, Re, Ru and W on transition temperatures in nickel-based superalloys with high γ′-volume fraction: Comparison of experiment and CALPHAD calculations, Metallurgical and Materials Transactions A, 2018, 49, 3206-3216.

[18] Sohrabi M.J., Mirzadeh H., Rafiei M., Solidification behavior and Laves phase dissolution during homogenization heat treatment of Inconel 718 superalloy, Vacuum, 2018, 154, 235-243.

[19] Radavich J.F., Loria (Ed.) E.A., The physical metallurgy of cast and wrought alloy 718, superalloy 718 metallurgy and applications, The Minerals, Metals & Materials Society, 1989.

[20] Cieslak M.J., Headley T.J., Knorovsky G.A., Romig A.D., Kolliea T., A comparison of the solidification behavior of Incoloy 909 and Inconel 718, Metallurgical and Materials Transactions, 1990, 21, 479-488.