Heat Treatment Microstructures of a Directionally Solidified Nickel Base Superalloy under High Temperature Gradient

Abstract:

The heat treatment of a directionally solidified superalloy under high temperature gradient with different dendritic size was studied. The evolution rules of each phase in DZ125 alloy after heat treatment were analyzed. The results show that γ' phase presents cube and uniform distribution after heat treatment. Its size is about 0.4μm and its area ratio is about 65%. MC carbide transforms into MC₍₂₎ carbide with high concentration of Hf. The morphology of MC carbide changes from Chinese-script to block and its size reduces gradually with increasing solidification rate under directional solidification. There is bulk γ' phase around carbide. MC₍₂₎ carbide and γ' phase in the grain boundary form chain along grain boundary, and effectively retard grain boundary sliding. γ+γ' eutectic is basically eliminated by solution treatment and only a little γ+γ' eutectic exists around carbide.

• Periodical: Materials Science Forum (Volume 788)
• Pages: 519-524
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.788.519
• Online since: April 2014
• Authors: Wei Guo Zhang, Xue Mei Yi*, Chu Ang Feng
• Keywords: Directional Solidification, Heat Treatment, High Temperature Gradient, Nickel-Based Superalloy

References

[1] L. Liu, J. Zhang, J. Shen, T.W. Huang, H.Z. Fu, Advances in directional solidification techniques of superalloys, Materials China. 29(2010) 1-9.

[2] A.J. Elliott, S. Tin, W.T. King, S.C. Huang, M. Gigliotti, Directional solidification of large superalloy castings with radiation and liquid-metal cooling: A comparative assessment, Metall. Mater. Trans. 35(2004) 3221-3231.

DOI: 10.1007/s11661-004-0066-z

[3] J. Zhang, L. Lou, Directional solidification assisted by liquid metal cooling, J. Mater. Sci. Technol. 23(2007) 289-299.

[4] M.L. Clemens, A. Price, R.S. Bellows. Advanced solidification processing of an industrial gas turbine engine component, JOM. 55(2003) 27-31.

DOI: 10.1007/s11837-003-0156-1

[5] Yu A. Bondarenko, E.N. Kablov, Directional crystallization of high-temperature alloys with elevated temperature gradient, Metal Sci. Heat Treat. 44 (2002) 288~291.

[6] L. Liu, F. Sommer, H.Z. Fu, Effect of solidification conditions on MC carbides in a Nickel-base superalloy IN738 LC, Script. Metall. Mater. 30(1994) 587-591.

DOI: 10.1016/0956-716x(94)90434-0

[7] M. Vijayakumar, S.N. Tewari, Dendrite spacing in directionally solidification alloy PWA-1480, Mater. Sci. Eng. A. 132(1991) 195-201.

DOI: 10.1016/0921-5093(91)90375-w

[8] P.C. Xia, W.F. Yu, J.J. Yu, W. L, X.F. Sun, H.R. Guan, Z.Q. Hu, Influence of standard heat treatment on microstructure and mechanical property of DZ951 alloy , Trans. Mater. heat treat. 29(2008) 96-99.

DOI: 10.1016/s1001-0521(08)60118-7

[9] H. Chen, J.X. Dong, M.C. Zhang, Effect of heat treatment process on microstructure of cast superalloy K480, Trans. Mater. Heat Treat. 33(2012) 37-44.

[10] S.R. Hegde R.M. Kearsey J.C. Beddoes, Designing homogenization-solution heat treatments for single crystal superalloys, Mater. Sci. Eng. A. 527(2010) 5528-5538.

DOI: 10.1016/j.msea.2010.05.019

[11] J.S. Li, W.M. Zhang, H.C. Kou, S.M. Li, F.S. Zhang, R. Hu, L. Liu, H.Z. Fu, Effect of structure refining on heat-treated structures and mechanical properties in single crystal superalloy, The Chinese Journal of Nonferrous Metals.12(2002) 290-293.

[12] W.G. Zhang, L. Liu, X.B. Zhao, T.W. Huang, Z.H. Yu, M. Qu, H.Z. Fu, Effect of directional solidification cooling rates on dendrite spacings of DZ125 alloy under high thermal gradient, Rare Met. 28(2009) 633-638.

DOI: 10.1007/s12598-009-0121-4

[13] W.G. Zhang, L. Liu, T.W. Huang, X.B. Zhao, Z.H. Yu, H.Z. Fu, Effect of cooling rate on γ' precipitate of DZ4125 alloy under high thermal gradient directional solidification, Acta Metall. Sin. 45(2009) 592-596.

[14] Y.Z. Shen, D.L. Lin, S.H. Huang, Mechanical properties and effect factors of new type directionally solidified superalloy, Mater. Mechanical Eng. 19(1995) 15-18.

[15] J.K. Tien, P.W. Keefe, J.P. Collier. The Role of Refractory Elements in Nickel-Base Superalloys, An Overview, ASM Conference on Refractory Alloying Elements in Superalloys, ASM Press, Metals Park, OH. (1984) 1–14.

DOI: 10.7449/1989/superalloys_1989_553_566

[16] W.G. Zhang, L. Liu, H.Z. Fu, Effect of cooling rate on MC carbide in directionally solidified nickel-based superalloy under high thermal gradient, China Foundry. 9(2012) 11-14.