Hot isostatic pressing impact on samples structure grown of Inconel 738 super alloy by selective laser melting technique

DOI: 10.34759/vst-2020-1-224-232

Аuthors

Dmitrieva M. O.^*, Golovach A. M.^**, Sotov A. V.^***

Samara National Research University named after Academician S.P. Korolev, 34, Moskovskoye shosse, Samara, 443086, Russia

*e-mail: mdmitr1ewa@yandex.ru
**e-mail: machete.ru2016@gmail.com
***e-mail: sotovanton@yandex.ru

Abstract

Selective Laser Melting (SLM) is an additive manufacturing technology intended for metal powders fusion by the high-power laser. Powder materials application ensures in this case more steady chemical composition over the product cross-section and zonal segregation absence.

One of the most important and complex trends in this technology consists in heat-resisting alloys powders application, since this particular is employed for the most critical parts manufacturing. Among the SLM technology benefits are the following:

– the possibility of manufacturing parts of any configuration complexity;

– the possibility of simultaneous growth of several samples;

– high materials utilization ratio, and products prototyping simplification

Disadvantages of the technology under consideration include the presence of residual porosity, restrictions on the employed materials and laser radiation sources s, as well as sizes of the products being fabricated.

The hot isostatic pressing (HIP) technique is applied to eliminate residual porosity. It consists in processing a part, set in a special capsule, by the gas pressure about 100-200 MPa at elevated temperatures. The purpose of the presented research is studying the HIP impact on the samples structure, grown of heat resisting Inconel 738 alloy by the SLM technique.

The samples being studied were fabricated on the SLM 280L installation for selective laser fusion of metal powder. They were synthesized both perpendicularly and at the angle of 45 degrees to the substrate at the laser radiation power of 325 W. The samples were being subjected to the HIP in the gas thermostat. After etching, the studies of microstructure were conducted with METAM LV-31 metallographic microscope. Electron-microscopic analysis of the samples and original powder material was performed with TESCAN Vega SB electron-scan microscope.

Chemical composition of the original powder material was being determined by INCAx-Act energy dispersive X-ray spectroscope. The microstructure analysis was performed with NEXSYS ImageExpert Pro 3 image analysis program. X-ray microanalysis revealed that chemical composition of the original powder of the heat resisting alloy complies with the Q/AMC 4-2-10­2018 certificate.

Original powder substance chemistry researched on an INCAx-Act energy dispersive X-ray spectroscope. Microstructure analysis was carried out using the NEXSYS ImageExpert Pro 3 image analysis program. X-ray microanalysis showed that the original powder substance chemistry corresponds to the Q/AMC 4-2-10-2018 certificate.

The results of electron-microscopic analysis of the original material allowed revealing that the powder particles were spherically shaped, characteristic to the technique for molten dispersing. Metallographic analysis of the sample grown vertically to the substrate at the laser radiation power of 325 W allowed establishing that microstructure represents an aggregate of fused powder particles, which were micro-ingots of the dendrite structure. After the SLM process, the microstructure of the sample cross-section is characterized by the defects such as micro-cracks. The microstructure of the sample cross-section, grown at 45 degrees to the substrate, is characterized by the presence of the same defects, but differs by their larger outstretch.

Metallographic analysis of the samples after HIP revealed that the structure defectiveness after the post processing decreased. Since the products were subjected to HIP without setting into the special capsule, healing of defects could not be attained. All surface defects remained in full, and internal ones reduced by the cross-section. The ineffectiveness of HIP application in this case is explained by the presence of chrome dioxide on the surface of powder particles, having formed under the impact of high temperatures while fusing.

Thus, the HIP technique application allowed decrease the structure defectiveness, due to micro cracks size reduction along the cross-section, but the full healing of defects was not attained. HIP effectiveness increase in this case is possible by placing the samples into the special airtight shell, and excluding chrome oxides forming on the powder particles by excluding metal-with-oxygen contact during the entire technological process.

Keywords:

nickel-base super alloy, microstructure, selective laser melting, electron microscopy, Inconel 738, hot isostatic pressing

References

1. Kablov E.N. Kryl’ya Rodiny, 2010, no. 4, pp. 31-33.

2. Sharova N.A., Tikhomirova E.A., Barabash A.L., Zhivushkin A.A., Brauer V.E. Vestnik Samarskogo gosudarstvennogo aerokosmicheskogo universiteta im. akademika S.P. Koroleva, 2009, no. 3-3(19), pp. 249-255.

3. Kablov E.N. Aviatsionnye materialy i tekhnologii, 2012, no. S, pp. 7-17.

4. Khryashchev I.I., Danilov D.V., Logunov A.V. Developing a sparingly doped high-temperature nickel alloy for gas turbine blades. Aerospace MAI Journal, 2019, vol. 26, no. 2, pp. 205-218.

5. Grashchenkov D.V., Shchetanov B.V., Efimochkin I.Yu. Vse materialy. Entsiklopedicheskii spravochnik, 2011, no. 5, pp. 13-26.

6. Sufiyarov V.Sh., Popovich A.A., Borisov E.V., Polozov I.A. Tsvetnye metally, 2015, no. 1, pp. 79-84.

7. Surikova M.A., Plechev V.N. Poroshkovaya metallurgiya zharoprochnykh splavov za rubezhom (Powder metallurgy of heat-resistant alloys abroad), Moscow, Chermetinformatsiya, 1982, 27 p.

8. Smurov I.Yu., Movchan I.A., Yadroitsev I.A., Okun’kova A.A., Tsvetkova E.V., Cherkasova N.Yu. Vestnik MGTU “Stankin”, 2011, no. 4(17), pp. 144-146.

9. Kablov E.N. Metally Evrazii, 2017, no. 1, pp. 2-6.

10. Ageev S.V., Girshov V.L. Metalloobrabotka. 2015, no. 4(88), pp. 56-60.

11. Beresnev A.G., Loghunov A.V., Loghachiova A.I. Some problems related to refinement of high- temperature alloys produced by means of granular metallurgy techniques. Aerospace MAI Journal, 2008, vol. 15, no. 3, pp. 83-89.

12. Zhang X., Chen H., Xu L., Xu J., Ren X., Chen X. Cracking mechanism and susceptibility of laser melting deposited Inconel 738 superalloy. Materials and Design, 2019, vol. 183, pp. 1-14. DOI: 10.1016/j.matdes.2019.108105

13. Ramakrishnan A., Dinda G.P. Direct laser metal deposition of Inconel 738. Materials Science and Engineering: A, 2019, vol. 740–740, pp. 1-13. DOI: 10.1016/j.msea.2018.10.020

14. Zhang D., Niu W., Cao X., Liu Z. Effect of standard heat treatment on the microstructure and mechanical properties of selective laser melting manufactured Inconel 718 superalloy. Materials Science and Engineering: A, 2015, vol. 644, pp. 32-40. DOI: 10.1016/j.msea.2015.06.021

15. Evgenov A.G., Rogalev A.M., Nerush S.V., Mazalov I.S. Trudy VIAM, 2015, no. 2. DOI: 10.18577/2307-6046-2015-0-2-2-2

16. Chabina E.B., Filonova E.V., Raevskikh A.N. Materialy II Mezhdunarodnoi konferentsii (16 March 2016, Moscow) “Additivnye tekhnologii: nastoyashchee i budushchee”, Moscow, VIAM, 2016, p. 4.

17. Maksimova S.V., Khorunov V.F. Novye materialy, 2010, no. 3, pp. 49-55.

18. Gryaznov M.Yu., Shotin S.V., Chuvil’deev V.N. Vestnik Nizhegorodskogo universiteta im. N.I. Lobachevskogo, 2014, no. 4(1), pp. 46-51.

19. Eremin E.N., Filippov Yu.O., Minnekhanov G.N., Mukhin V.F. Omskii nauchnyi vestnik, 2011, no. 3(103), pp. 65-70.

20. Evgenov A.G., Nerush S.V., Vasilenko S.A. Trudy VIAM, 2014, no. 5. DOI: 10.18577/2307-6046-2014-0-5-4-4

21. Nerush S.V., Evgenov A.G. Trudy VIAM, 2014, no. 3. DOI: 10.18577/2307-6046-2014-0-3-1-1

22. Sukhov D.I., Bazyleva O.A., Nerush S.V., Arginbaeva E.G., Zaitsev D.V. Materialy IV Mezhdunarodnoi konferentsii (30 March 2018, Moscow) “Additivnye tekhnologii: nastoyashchee i budushchee ”, Moscow, VIAM, 2018, pp. 368-372. URL: https://conf.viam.ru/sites/default/files/uploads/proceedings/1073.pdf

23. Nerush S.V., Evgenov A.G., Ermolaev A.S., Rogalev A.M. Voprosy materialovedeniya, 2013, no. 4(76), pp. 98-107.

24. Smelov V.G., Sotov A.V., Agapovichev A.V. Chernye metally, 2016, no. 9(1017), pp. 61-65.

25. Sotov A.V., Pronichev N.D., Smelov V.G., Bogdanovich V.I., Giorbelidze M.G., Agapovichev A.V. Izvestiya Samarskogo nauchnogo tsentra Rossiiskoi akademii nauk, 2017, vol. 19, no. 4, pp. 96-104.