Peter the Great Saint Petersburg Polytechnic University, Saint Petersburg, Russia:

V. Sh. Sufiiarov, Leading Researcher, e-mail: vadim.spbstu@yandex.ru
A. A. Popovich, Director of Institute of Metallurgy, Mechanical Engineering and Transport
E. V. Borisov, Post-Graduate, Researcher
I. A. Polozov, Student, Engineer

The paper describes the integrated research of selective laser melting of heat-resistant nickel alloy Inconel 718. The research findings describe morphology, particle size distribution, evolution of structure and phase composition of the nickel alloy produced by gas atomization. Based on the study results, the powder particles possess good flowability, has more than 90% content of -Ni phase, and the shape of the particles is close to spherical, though some particles have satellites. The authors analyzed the influence exerted by the parameters of selective laser melting on the alloy specimen porosity. The variable parameters were assumed to be laser power, scanning speed and hatch distance. It follows from the research outcome that the best results (relative density 99.7%) are achieved with the laser power of 245 W, scanning speed of 755 mm/s and hatch distance of 90 μm. The mechanical properties of Inconel 718 alloy specimens shows that the strength and plasticity properties of Inconel 718 are comparable with these properties of the specimens manufactured by casting without thermal treatment. In particular, the ultimate tensile strength of the test specimens is 851–949 MPa, yield stregth is 569–609 MPa and the relative elongation is 9.8–31.7%. The further improvement of quality of SLM products needs heat treatment aimed at optimization of phase composition and structure as well as removal of thermal and residual stresses.

This work was carried out with financial State support by the Ministry of Education and Science according to the grant agreement № 14.626.21.0001 (unique identifier RFMEFI62614X0001) under the Federal Target Program “Research and development on priority directions of scientific-technological complex of Russia for 2014–2020”

1. Chester T. Sims, Norman S. Stoloff, William C. Hagel. Supersplavy II: Zharoprochnye materialy dlya aerokosmicheskikh i energeticheskikh ustanovok (Superalloys II: Heat-resistant materials for aerocosmic and energetic units). Moscow : Metallurgiya, 1995. 385 p.
2. Reed R. C. The Superalloys. Fundamentals and Applications. New York : Cambridge university press, 2006. 372 p.
3. Proceedings of 12^th International Symposium on Superalloys. New Jersey : John Wiley & Sons Inc., 2012. 904 p.
4. Zlenko M. A., Popovich A. A., Mutylina I. N. Additivnye tekhnologii v mashinostroenii (Additive technologies in machine-building). Saint Petersburg : Publishing House of Polytechnical University, 2013. 222 p.
5. Nerush S. V., Evgenov A. G., Ermolaev A. S., Rogalev A. M. Issledovanie melkodispersnogo metallicheskogo poroshka zharoprochnogo splava na nikelevoy osnove dlya lazernoy LMD naplavki (Research of fine-disperse metallic powder of heat-resistant nickelbased alloy for laser LMD building-up). Voprosy materialovedeniya = Inorganic Materials: Applied Research. 2013. No. 4. pp. 98–107.
6. Jia Q., Gu D. Selective laser melting additive manufacturing of Inconel 718 superalloy parts: Densification, microstructure and properties. Journal of Alloys and Compounds. 2014. Vol. 585. pp. 713–721.
7. Jia Q., Gu D. Selective laser melting additive manufactured Inconel 718 superalloy parts: High-temperature oxidation property and its mechanisms. Optics & Laser Technology. 2014. Vol. 62. pp. 161–171.
8. ISO 13320:2009. Granulometricheskiy analiz. Metody lazernoy difraktsii (ISO 13320:2009. Granulometric analysis. Laser diffraction methods). (in Russian).
9. GOST 20899–98. Poroshki metallicheskie. Opredelenie tekuchesti s pomoshchyu kalibrovannoy voronki (pribora Kholla) (State Standard 20899–98. Metallic powders. Definition of flow rate by calibrated riser (Hall unit)). Introduced: 2001–07–01. (in Russian).
10. GOST 1497–84. Metally. Metody ispytaniy na rastyazhenie (State Standard 1497–84. Metals. Pull test methods). Introduced: 1986–01–01. (in Russian).
11. Libenson G. A., Lopatin V. Yu., Komarnitskiy G. V. Protsessy poroshkovoy metallurgii. Tom 1. Proizvodstvo metallicheskikh poroshkov (Processes of powder metallurgy. Volume 1. Production of metallic powders). Moscow : MISiS, 2001. 368 p.
12. Sufiyarov V. Sh. Analiz i modelirovanie protsessov formirovaniya dendritnoy neodnorodnosti v stalyakh s tselyu ee ustraneniya. Dissertatsiya … kandidata tekhnicheskikh nauk (Analysis and modeling of processes of formation of dendrite inhomogeneity in steels for the purpose of its removal. Dissertation of Candidate of Engineering Sciences). Saint Petersburg : Saint-Petersburg State polytechnical University, 2013. 189 p.
13. Wang Z., Guan K., Gao M., Li X., Chen X., Zeng X. The microstructure and mechanical properties of deposited-IN718 by selective laser melting. Journal of Alloys and Compounds. 2012. Vol. 513. pp. 518–523.
14. Yasa E., Deckers J., Kruth J. The investigation of the influence of laser re-melting on density, surface quality and microstructure of selective laser melting parts. Rapid Prototyping Journal. 2011. Vol. 17, No. 5. pp. 312–327.
15. Amato K. N., Gaytan S. M., Murr L. E., Martinez E., Shindo P. W., Hernandez J., Collins S., Medina F. Microstructures and mechanical behavior of Inconel 718 fabricated by selective laser melting. Acta Materialia. 2012. Vol. 60, No. 5. pp. 2229–2239.
16. Yadroitsev I., Smurov I. Selective laser melting technology: from the single laser melted track stability to 3D parts of complex shape. Physics Procedia. 2010. Vol. 5. pp. 551–560.
17. El-Bagoury N., Matsuba T., Yamamoto K., Miyahara H., Ogi K. Influence of Heat Treatment on the Distribution of Ni₂Nb and Microsegregation in Cast Inconel 718 Alloy. Materials Transactions. 2005. Vol. 46, No. 11. pp. 2478–2483.