Investigation of the stress rupture behavior of GTD-111 superalloy melted by VIM/VAR

Abstract

The effects of vacuum induction melting (VIM) and vacuum arc remelting (VAR) processes on the microstructure and stress rupture properties of Ni-based GTD-111 superalloy were investigated. Samples of GTD-111 master alloy were melted in VIM and VAR furnaces and then poured into a preheated ceramic mold for VIM melt or into a water-cooled copper mold for VAR melt. The as-cast samples were examined radiographically to ensure that no casting defects were present in the final castings; the samples were then heat-treated using a standard heat-treatment cycle. The microstructure of the samples was investigated using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy for microanalysis. On the basis of standard ASTM-E139, stress rupture tests were carried out at 1000°C under a stress of 300 MPa. The results showed that a γ matrix, fine γ′ precipitates, a γ–γ′ eutectic structure, carbide particles, and some harmful phases such as σ and η phases were present in the as-cast samples. The γ′ precipitates with cubic morphology appeared in the matrix after the standard heat-treatment process. The extent of segregation and the amount of γ–γ′ eutectic structure formed in the VAR-prepared sample were less than in the VIM-prepared sample. The results of stress rupture tests showed that the rupture time for the VAR sample was 43% longer than that for the VIM sample.

Keywords

GTD-111 / vacuum induction melting (VIM) / vacuum arc remelting (VAR) / stress rupture

References

[1] Sajjadi S.A., Nategh S., Guthrie R.I.L. Study of microstructure and mechanical properties of high performance Ni-base superalloy GTD-111. Mater. Sci. Eng. A, 2002, 325(1-2): 484.

[2] Choi B.G., Kim I.S., Kim D.H., Jo C.Y. Temperature dependence of MC decomposition behavior in Ni-base superalloy GTD 111. Mater. Sci. Eng. A, 2008, 478(1-2): 329.

[3] Kim H.I., Park H.S., Koo J.M., Seok C.S., Yang S.H., Kim M. Y. J. Mech. Sci. Technol., 2012

[4] Sajjadi S.A., Zebarjad S.M., Guthrie R.I. L., Isac M. Microstructure evolution of high-performance Ni-base superalloy GTD-111 with heat treatment parameters. J. Mater. Process. Technol., 2006, 175(1–3): 376.

[5] Yang C.X., Xu Y.L., Zhang Z.X., Nie H., Xiao X.S., Jia G.Q., Shen Z. Improvement of stress-rupture life of GTD-111 by second solution heat treatment. Mater. Des., 2013, 45, 308.

[6] Sajjadi S.A., Nategh S. A high temperature deformation mechanism map for the high performance Ni-base superalloy GTD-111. Mater. Sci. Eng. A, 2001, 307(1-2): 158.

[7] Sathian S. Metallurgical and Mechanical Properties of Ni-Based Superalloy Friction Welds [Dissertation], 1999, Toronto, University of Toronto.

[8] Sajjadi S.A., Nategh S., Isac M., Zebarjad S.M. Tensile deformation mechanisms at different temperatures in the Ni-base superalloy GTD-111. J. Mater. Process. Technol., 2004, 155, 1900.

[9] Nategh S., Sajjadi S.A. Dislocation network formation during creep in Ni-base superalloy GTD-111. Mater. Sci. Eng. A, 2003, 339(1-2): 103.

[10] Yu J.J., Sun X.F., Jin T., Zhao N.R., Guan H.R., Hu Z.Q. High temperature creep and low cycle fatigue of a nickel-base superalloy. Mater. Sci. Eng. A, 2010, 527(9): 2379.

[11] ASTM, E139-11, Standard Test Method for Conducting Creep, Creep-Rupture and Stress-Rupture Tests of Metallic Materials, American Society for Testing and Materials, Philadelphia, 2011.

[12] Ding J., Jiang S., Li Y.M., Wu Y.T., Wu J., Peng Y.Y., He X., Xia X.C., Li C., Liu Y.C. Microstructure evolution behavior of Ni3Al (γ′) phase in eutectic γ-γ′ of Ni3Al-based alloy. Intermetallics, 2018, 98, 28.

[13] Kakitani R., Reyes R.V., Garcia A., Spinelli J.E., Cheung N. Relationship between spacing of eutectic colonies and tensile properties of transient directionally solidified Al−Ni eutectic alloy. J. Alloys Compd., 2018, 733, 59.

[14] Smith W.F. Structure and Properties of Engineering Alloys, 1987, New York, McGraw-Hill.

[15] Liu J.L., Jin T., Yu J.J., Sun X.F., Guan H.R., Hu Z.Q. Effect of thermal exposure on stress rupture properties of a Re bearing Ni base single crystal superalloy. Mater. Sci. Eng. A, 2010, 527(4-5): 890.

[16] Ansell G.S., Weertman J.W. Creep of Dispersion-Hardened Aluminum Alloy, 1958, Washington DC, Naval Research Lab..

[17] Chang H.J., Fivel M.C., Strudel J.L. Micromechanics of primary creep in Ni base superalloys. Int. J. Plast., 2018, 108, 21.