Influence of Withdrawal Rate on As-Cast Microstructure and Stress-Rupture Life of Directionally Solidified Rene80 Superalloy
محورهای موضوعی : Superalloyssobhan Rajabi nejad 1 , Masumeh seifollahi 2 , seyed mahdi Abbasi 3 , Seyed Mahdi Ghazi mirsaeed 4
1 - Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
2 - Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
3 - Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
4 - Faculty of Materials and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
کلید واژه: Rene80, DS superalloy, dendritic structure, microporosity, Stress-rupture,
چکیده مقاله :
The purpose of this study is to investigate the effects of withdrawal rate on the dendrite microstructure and its formation mechanism, the porosity, and the interaction between them in Rene 80 superalloy. So, Rene 80 Ni-base superalloy was directionally solidified on a laboratory scale using the Bridgman method. The cylindrical rods were grown at withdrawal rates of 2, 4, 6, 8, and 10 mm.min-1. Dendritic structure and solidification microporosities were evaluated in transverse and longitude sections. The results showed that when the withdrawal rate was increased, the primary and secondary dendritic arm spacing decreased. With an increasing withdrawal rate, which causes to decrease in the dendritic arms spacing, the volume fraction of inter-dendritic gamma prime was first decreased until the rate of 6 mm.min-1, and after that, its volume fraction increased. This structure results from peritectic and eutectic transformations with checkerboard-like and fan-like morphology, respectively. Moreover, the volume fraction of microporosities was minimal at the rate of 6 mm.min-1, while their average size decreased from 13.2 to 8.7 μm. The specimens were given a two-stage heat treatment followed by a stress rupture test at 191 MPa and 980˚C. It was shown that at R=6 mm.min-1, directionally solidified rods with a less solidification microporosity and well-orientated dendritic structure give higher rupture life of 25.43 hrs.
[1] R. C. Reed. The superalloys: fundamentals and applications. Cambridge: Cambridge university press; 2008.
[2] C. Yang, Y. Xu, H. Nie, “Effects of heat treatments on the microstructure and mechanical properties of Rene 80”, Mater. Des., Vol. 43, 2013, pp. 66–73.
[3] A. Ohtomo, Y. Saiga, “Directional solidification of Rene’ 80”, Jpn. Inst. Met. Trans., Vol 17, 1976, pp 323–329.
[4] H. Zhang, O. A. Ojo. J. Mater. Sci. “TEM analysis of Cr–Mo–W–B phase in a DS nickel based superalloy”, Vol. 43, 2008, pp. 6024–6028.
[5] T. Goswami, H. Hänninen, “Dwell effects on high temperature fatigue behavior –. Part I.”, Mater. Des., Vol.22, 2001, pp. 199–215.
[6] R. K. Sidhu, O. A. Ojo, M. C. Chaturvedi, “Sub-solidus melting of directionally solidified Rene 80 superalloy during solution heat treatment”, J. Mater. Sci., Vol. 43, 2008, pp. 3612–3617.
[7] A. Szczotok, B. Chmiela, “Effect of Heat Treatment on Chemical Segregation in CMSX-4 Nickel-Base Superalloy”, J. Mater. Eng. Perform., Vol. 23, 2014, pp. 2739–2747.
[8] L. Kunz, P. Lukáš, R. Konečná, “Casting defects and high temperature fatigue life of IN713LC superalloy”, Int. J. Fatigue., Vol. 41, 2012, pp. 47–51.
[9] Q. Yue, L. Liu, W. Yang, “Influence of withdrawal rate on the porosity in a third generation Ni based superalloy”, Prog. Nat. Sci.: Mater. Int., Vol. 61, 2017, pp. 236–243.
[10] B. S. Bokstein, A. I. Epishin, T. Link, “Model for the porosity growth in single crystal nickel base superalloys during homogenization”, Scr. Mater., Vol. 57, 2007, pp. 801–804.
[11] T. Link, S. Zabler, A. Epishin , “Synchrotron tomography of porosity in single crystal nickel base superalloys”, Mater. Sci. Eng., Vol. 425A, 2006, pp. 47–54.
[12] E. Bachelet, G. Lesoult, “Quality of castings of superalloys. In: High Temperature Alloys for Gas Turbines”, Liege, Belgium, 1978, pp. 665-699.
[13] S. Roskosz, M. Staszewski, A. Cwajna. “A complex procedure for describing porosity in precision cast elements of aircraft engines made of MAR-M 247 and MAR-M 509 superalloys”, J. Mater. charact., Vol. 56, 2006, pp.405–413.
[14] J. Zhang, J. Li, T. Jin, “Effect of solidification parameters on the microstructure and creep property of a single crystal Ni base superalloy”, J. Mater., Vol. 26, 2010, pp. 889–895.
[15] G. Sifeng , L. Lin , X. Yiku , “Influence of processing parameters on microstructure during investment casting of nickel base single crystal superalloy DD3”, China Foundry, Vol. 9, 2012, pp.159–164.
[16] M. M. Zou, J. Zhang, J. G. Li, “Effect of melt overheating history on the microstructure of Ni-Base single crystal superalloy”, Adv. Mater. Res., Vol, 217, 2011, 692–696.
[17] G. Liu, L. Liu, C. Ai, “Influence of withdrawal rate on the microstructure of Ni-base single-crystal superalloys containing Re and Ru”, J. Alloys Compd., Vol. 509, 2011, pp. 5866–5872.
[18] J. D. Hunt, “Cellular and primary dendrite spacing. In: Solidification and Casting of Metals”, Sheffield, England, 1977, pp. 3-9.
[19] W. Kurz, D. J. Fisher, “Dendrite growth at the limit of stability”, Acta Metall., Vol 29, 1981, pp. 11–20.
[20] R. Trivedi, “Interdendritic spacing: Part II. A comparison of theory and experiment”, Metall. Mater. Trans., Vol. 15A, 1984, pp. 977–982.
[21] T. Z. Kattamis, M. C. Flemings, “ Dendrite morphology, micro-segregation, and homogenization of low-alloy steel”, Transactions of the Metallurgical Society of AIME, Vol 233,1965, pp. 992-999.
[22] L. G. Peterson, “Directional solidification of land based gas. In: ASME 1989 International Gas Turbine and Aeroengine Congress and Exposition” American Society of Mechanical Engineers. 1989, pp. 332-337.
[23] N. Warnken N, “Studies on the solidification path of single crystal superalloys”, J. Phase Equilib. Diffus., Vol. 37, 2016, pp.100–107.
[24] N. D’souza, H. B., Dong, “Solidification path in third-generation Ni-based superalloys with an emphasis on last stage solidification”, Scr. Mater., Vol 56, 2007, pp. 41–44.
[25] A. Heckl, R. Rettig, S. Cenanovic, “Investigation of the final stages of solidification and eutectic phase formation in Re and Ru containing nickel-base superalloys” J. Cryst. Growth., Vol. 312, 2010, pp.2137–2144.
[26] Porter DA, Easterling KE, Sherif M. “Phase Transformations in Metals and Alloys”. United States: CRC press; 2009.
[27] P. Shewmon, “Diffusion in solids”, Springer, 2016.
[28] Y. G. Nakagava, A. Ohtomo and Y. Saiga, “Directional solidification of Rene 80”, Trans. Japan Institute Met., Vol. 17, pp. 323-329, 1976.
