Optimization of the heat treatment of additively manufactured Ni-base superalloy IN718

Abstract

Additive manufacturing (AM) of Ni-base superalloy components can lead to a significant reduction of weight in aerospace applications. AM of IN718 by selective laser melting results in a very fine dendritic microstructure with a high dislocation density due to the fast solidification process. The complex phase composition of this alloy, with three different types of precipitates and high residual stresses, necessitates adjustment of the conventional heat treatment for AM parts. To find an optimized heat treatment, the microstructures and mechanical properties of differently solution heat-treated samples were investigated by transmission and scanning electron microscopy, including electron backs-catter diffraction, and compression tests. After a solution heat treatment (SHT), the Nb-rich Laves phase dissolves and the dislocation density is reduced, which eliminates the dendritic substructure. SHT at 930 or 954°C leads to the precipitation of the δ-phase, which reduces the volume fraction of the strengthening γ′- and γ″-phases formed during the subsequent two stage aging treatment. With a higher SHT temperature of 1000°C, where no δ-phase is precipitated, higher γ′ and γ″ volume fractions are achieved, which results in the optimum strength of all of the solution heat treated conditions.

Keywords

Ni-base superalloy / selective laser melting / strengthening mechanism / powder bed fusion / microstructure

References

[1] Nickels L. AM and aerospace: An ideal combination. Met. Powder Rep., 2015, 70(6): 300.

[2] S. Soller, R. Behr, F. Laithier, M. Lehmann, A. Preuss, and R. Salapete, Design and testing of liquid propellant injectors for additive manufacturing, [in] 7th European Conference for Aerospace Sciences, Milan, 2017, p. 306.

[3] N. Arjakine, J. Bruck, B. Grüger, D.M. Seeger, and R. Wilkenhoener, Advanced weld repair of gas turbine hot section components, [in] ASME Turob Expo 2008: Power for Land, Sea and Air, Berlin, 2008, p. 559.

[4] Jia QB, Gu DD. Elective laser melting additive manufacturing of Inconel 718 superalloy parts: Densification, microstructure and properties. J. Alloys Compd., 2014, 585, 713.

[5] Lee YS, Zhang W. Modeling of heat transfer, fluid flow and solidification microstructure of nickel-base superalloy fabricated by laser powder bed fusion. Addit. Manuf., 2016, 12, 178.

[6] Raghavan N, Dehoff R, Pannala S, Simunovic S, Kirka M, Turner J, Carlson N, Babu SS. Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing. Acta Mater., 2016, 112, 303.

[7] Mercelis P, Kruth JP. Residual stresses in selective laser sintering and selective laser melting. Rapid Prototyp. J., 2006, 12(5): 254.

[8] Mei YP, Liu YC, Liu CX, Li C, Yu LM, Guo QY, Li HJ. Effect of base metal and welding speed on fusion zone microstructure and HAZ hot-cracking of electron-beam welded Inconel 718. Mater. Des., 2016, 89, 964.

[9] Raza T, Hurtig K, Asala G, Andersson J, Svensson LE, Ojo OA. Influence of heat treatments on heat affected zone cracking of gas tungsten arc welded additive manufactured alloy 718. Metals, 2019, 9(8): 881.

[10] Mertens R, Vrancken B, Holmstock N, Kinds Y, Kruth JP, Van Humbeeck J. Influence of powder bed preheating on microstructure and mechanical properties of H13 tool steel SLM parts. Phys. Procedia, 2016, 83, 882.

[11] B. Vrancken, S. Buls, J.P. Kruth, and J. Van Humbeeck, Preheating of selective laser melted Ti6Al4V: Microstructure and mechanical properties, [in] Proceedings of the 13th World Conference on Titanium, San Diego, 2016, p. 1269.

[12] Lee Y, Nordin M, Babu SS, Farson DF. Effect of fluid convection on dendrite arm spacing in laser deposition. Metall. Mater. Trans. B, 2014, 45(4): 1520.

[13] Liu PW, Wang Z, Xiao YH, Horstemeyer MF, Cui XY, Chen L. Insight into the mechanisms of columnar to equiaxed grain transition during metallic additive manufacturing. Addit. Manuf., 2019, 26, 22.

[14] Pröbstle M, Neumeier S, Hopfenmüller J, Freund LP, Niendorf T, Schwarze D, Göken M. Superior creep strength of a nickel-based superalloy produced by selective laser melting. Mater. Sci. Eng. A, 2016, 674, 299.

[15] Zhang DY, Niu W, Cao XY, Liu Z. Effect of standard heat treatment on the microstructure and mechanical properties of selective laser melting manufactured Inconel 718 superalloy. Mater. Sci. Eng. A, 2015, 644, 32.

[16] Tucho WM, Cuvillier P, Sjolyst-Kverneland A, Hansen V. Microstructure and hardness studies of Inconel 718 manufactured by selective laser melting before and after solution heat treatment. Mater. Sci. Eng. A, 2017, 689, 220.

[17] Ni XQ, Kong DC, Wen Y, Zhang L, Wu WH, He BB, Lu L, Zhu DX. Anisotropy in mechanical properties and corrosion resistance of 316L stainless steel fabricated by selective laser melting. Int. J. Miner. Metall. Mater, 2019, 26(3): 319.

[18] Vilaro T, Colin C, Bartout JD, Nazé L, Sennour M. Microstructural and mechanical approaches of the selective laser melting process applied to a nickel-base superalloy. Mater. Sci. Eng. A, 2012, 534, 446.

[19] Kuo YL, Horikawa S, Kakehi K. Effects of build direction and heat treatment on creep properties of Ni-base superalloy built up by additive manufacturing. Scripta Mater., 2017, 129, 74.

[20] Chlebus E, Gruber K, Kuźnicka B, Kurzac J, Kurzynowski T. Effect of heat treatment on the microstructure and mechanical properties of Inconel 718 processed by selective laser melting. Mater. Sci. Eng. A, 2015, 639, 647.

[21] Helmer HE, Körner C, Singer RF. Additive manufacturing of nickel-based superalloy Inconel 718 by selective electron beam melting: Processing window and microstructure. J. Mater. Res, 2014, 29(17): 1987.

[22] Amato KN, Gaytan SM, Murr LE, Martinez E, Shindo PW, Hernandez J, Collins S, Medina F. Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting. Acta Mater., 2012, 60(5): 2229.

[23] Rao GA, Kumar M, Srinivas M, Sarma DS. Effect of standard heat treatment on the microstructure and mechanical properties of hot isostatically pressed superalloy inconel 718. Mater. Sci. Eng. A, 2003, 355(1–2): 114.

[24] Raghavan S, Zhang BC, Wang P, Sun CN, Nai MLS, Li T, Wei J. Effect of different heat treatments on the microstructure and mechanical properties in selective laser melted INCONEL 718 alloy. Mater. Manuf. Processes, 2017, 32(14): 1588.

[25] Antonsson T, Fredriksson H. The effect of cooling rate on the solidification of INCONEL 718. Metall. Mater. Trans. B, 2005, 36(1): 85.

[26] Azadian S, Wei LY, Warren R. Delta phase precipitation in Inconel 718. Mater. Charact., 2004, 53(1): 7.

[27] Sundararaman M, Mukhopadhyay P, Banerjee S. Some aspects of the precipitation of metastable intermetallic phases in INCONEL 718. Metall. Mater. Trans. A, 1992, 23(7): 2015.

[28] Cozar R, Pineau A. Morphology of γ′ and γ″ precipitates and thermal stability of inconel 718 type alloys. Metall. Trans., 1973, 4(1): 47.

[29] Zhang HJ, Li C, Guo QY, Ma ZQ, Li HJ, Liu YC. Improving creep resistance of nickel-based superalloy Inconel 718 by tailoring gamma double prime variants. Scripta Mater., 2019, 164, 66.

[30] Martorano MA, Biscuola VB. Columnar front tracking algorithm for prediction of the columnar-to-equiaxed transition in two-dimensional solidification. Modell. Simul. Mater. Sci. Eng., 2006, 14(7): 1225.

[31] Liu J, To AC. Quantitative texture prediction of epitaxial columnar grains in additive manufacturing using selective laser melting. Addit. Manuf., 2017, 16, 58.

[32] Acharya R, Sharon JA, Staroselsky A. Prediction of microstructure in laser powder bed fusion process. Acta Mater., 2017, 124, 360.

[33] Zhao XM, Chen J, Lin X, Huang WD. Study on microstructure and mechanical properties of laser rapid forming Inconel 718. Mater. Sci. Eng. A, 2008, 478(1–2): 119.

[34] Deng DY, Moverare J, Peng RL, Söderberg H. Microstructure and anisotropic mechanical properties of EBM manufactured Inconel 718 and effects of post heat treatments. Mater. Sci. Eng. A, 2017, 693, 151.

[35] Thiede T, Cabeza S, Mishurova T, Nadammal N, Kromm A, Bode J, Haberland C, Bruno G. Residual stress in selective laser melted Inconel 718: Influence of the removal from base plate and deposition hatch length. Mater. Perform. Charat., 2018, 7(4): 1.

[36] Nadammal N, Cabeza S, Mishurova T, Thiede T, Kromm A, Seyfert C, Farahbod L, Haberland C, Schneider JA, Portella PD, Bruno G. Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718. Mater. Des., 2017, 134, 139.

[37] Liu Y, Yang YQ, Wang D. A study on the residual stress during selective laser melting (SLM) of metallic powder. Int. J. Adv. Manuf. Technol., 2016, 87(1): 647.

[38] Schneider J, Lund B, Fullen M. Effect of heat treatment variations on the mechanical properties of Inconel 718 selective laser melted specimens. Addit. Manuf., 2018, 21, 248.

[39] Sangid MD, Book TA, Naragani D, Rotella J, Ravi P, Finch A, Kenesei P, Park JS, Sharma H, Almer J, Xiao XH. Role of heat treatment and build orientation in the microstructure sensitive deformation characteristics of IN718 produced via SLM additive manufacturing. Addit. Manuf., 2018, 22, 479.

[40] Desvallées Y, Bouzidi M, Bois F, Beaude N. Loria EA. Delta phase in Inconel 718: Mechanical properties and forging process requirements. Superalloys 718, 625, 706 and Various Derivatives, 1994, Warrendale, The Minerals, Metals & Materials Society, 281.