Prediction of Grain Formation and Defects during Solidification in Single Crystal Superalloy Castings

Abstract:

Numerical simulation and prediction of grain formation and defects, including the stray grain and high angle orientation deviation during directional solidification process of a single crystal superalloy hollow turbine blade are experimentally conducted by means of commercial software ProCAST and backscattering scanning electron microscope. The results show that the initial nucleation amount at the beginning section of the starter block is 10⁴ of magnitude, and the number of grains decreases gradually with the competitive growth, and the number is about 100 at the spiral of the selector. And the orientation distribution of grains is close to <001> direction, with the orientation deviation between 10° and 15°. Moreover, with the increase of withdrawal rate, the curvature of isoline of liquidus of single crystal blade increases, and the tendency to form stray grains defects increases. The grain with a large deviation from orientation blocks the growth of other grains at the first rotating transition site of the selector, and then gradually grows and solidifies to form the final blade.

• Periodical: Materials Science Forum (Volume 1035)
• Pages: 819-826
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.1035.819
• Online since: June 2021
• Authors: Hai Peng Jin*, S.Z Liu, Hong Ji Xie, Jia Rong Li
• Keywords: Grain Competition Growth, High Angle Deviation, Prediction, Single Crystal Superalloy Castings, Stray Grains

References

[1] Szeliga D P, Kubiak K, Motyka M, et al.. Directional solidification of Ni-based superalloy castings: Thermal analysis [J]. Vacuum, 2016, 131: 327-342.

DOI: 10.1016/j.vacuum.2016.07.009

[2] Jia Z H, Ma A L, Zhao Y T, et. al.. Simulation and experimental analysis on crystal selection behavior of spiral grain selector for single crystal superalloy[J]. Special Casting & Nonferrous Alloys, 2019, 39(3): 242-246.

[3] Ning Wang, Lin Liu, Sifeng Gao, Xinbao Zhao, Taiwen Huang, Jun Zhang, Hengzhi Fu. Simulation of grain selection during single crystal casting of a Ni-base superalloy[J]. Journal of Alloys and Compounds, 2014, 586: 220-229.

DOI: 10.1016/j.jallcom.2013.10.036

[4] Yang C B, Liu L, Ning L, et. al.. Orientation characteristics of single crystal super alloys with different preparation methods[J]. Rare Metal materials and Engineering, 2017, 46(4): 912-916.

DOI: 10.1016/s1875-5372(17)30121-2

[5] Roger C. Reed. The superalloy fundamentals and applications. Cambridge University Press. UK, (2006).

[6] Hong-Qi Z, Jun Z, Ya-Feng L I, et al. Stray grain formation in casting platform of third generation Ni-base single crystal superalloy[J]. Foundry, 2014, 63(2): 128-131.

[7] Rezaei M, Kertmanpur A, Sadeghi F. Effects of withdrawal rate and starter block size on crystal orientation of a single crystal Ni-based superalloy [J]. Journal of crystal growth, 2018, 485: 19-27.

DOI: 10.1016/j.jcrysgro.2017.12.040

[8] Yang X, Dong H, Wang W, et al.. Microscale simulation of stray grain formation in investment cast turbine blades[J]. Materials Science and Engineering A, 2004, 386(1-2): 129-139.

DOI: 10.1016/s0921-5093(04)00914-1

[9] Anderson T D, Dupont J N, Debroy T. Origin of stray grain formation in single-crystal superalloy weld pools from heat transfer and fluid flow modeling[J]. Acta Materialia, 2010, 58(4):1441-1454.

DOI: 10.1016/j.actamat.2009.10.051

[10] Xuan W D, Ren Z M, Liu H, et al. Formation of stray grains in directionally solidified Ni-based superalloy with cross-section change regions[J]. Materials Science Forum, 2013, 747-748:535-539.

DOI: 10.4028/www.scientific.net/msf.747-748.535

[11] A. B. Shapiro, TOPAZ: A finite element heat conduction code for analyzing 2-D solids, Lawrence Livermore Laboratory, California (1984).

[12] ProCAST-The Professional Casting simulation system user manual, Universal Energy Systems, Inc., Ohio, (1988).

[13] R. W. Lewis and P. M. Roberts: Modeling the flow and solidification of metals, ed. T. J. Smith, Boston (1987).

[14] P. Thevoz, J.-L. Debiolles and M. Rappaz. Modeling of equiaxed microstructure formation in casting[J]. Metallurgical and Materials Transactions A. 1989, 20A: 311-322.

DOI: 10.1007/bf02670257

[15] W. Kurz, B. Giovanola, R. Trivedi. Theory of Microstructural Development During Rapid Solidification[J]. Acta Metallurgica, 1986, 34(5): 823-830.

DOI: 10.1016/0001-6160(86)90056-8

[16] M. Rappaz and Ph. Thevoz. Solute diffusion model for equiaxed dendritic growth[J]. Acta Metallurgica, 1987, 35: 1487-1497.

DOI: 10.1016/0001-6160(87)90094-0

[17] A. De Bussac, Ch.-A. Gandin. Prediction of a process window for the investment casting of dendritic single crystals[J]. Materials Science and Engineering, 1997, A237: 35-42.

DOI: 10.1016/s0921-5093(97)00081-6