Surface Roughness Improvement of PBF-LB Manufactured 316L with Dry Electropolishing

Abstract:

Laser powder bed fusion (PBF-LB) technique can currently offer the lowest surface roughness among all available techniques for metal additive manufacturing. Still the measured values for R_a can easily be over 10 μm depending on the used layer thickness and printing parameters. The current work focuses on improving the surface roughness by utilizing dry electropolishing machine. While suitable for many materials, the material selected for this study is one of the most used in PBF-LB manufacturing, stainless steel 316L. In addition, multistep pre-grinding with the grade of the final finish varied was used to investigate what is the most efficient way to distribute manual preparation work and automated polishing to reach the desired surface roughness. Furthermore, severe shot peening was used before the polishing to study the effect on residual stresses and fatigue life of the material. Laser optical microscopy was used to investigate the surface properties and it was found that dry electropolishing with pre-grinding could be succesfully used to obtain average roughness levels as low as 0.13 μm. The highest reductions in surface roughness were reached with the rougher initial surfaces where it could be reduced by 80% at best. Residual stresses measured after the severe shot peening were preserved after the polishing but did not result in increased fatigue strength.

• Periodical: Key Engineering Materials (Volume 972)
• Pages: 3-12
• DOI: https://doi.org/10.4028/p-SaeI5W
• Online since: December 2023
• Authors: Timo Rautio*, Matias Jaskari, Antti Järvenpää
• Keywords: 316L, Dry Electropolishing, PBF-LB, Polishing, Surface Quality

References

[1] K. Ishfaq, M. Asad, M.A. Mahmood, M. Abdullah, and C. Pruncu. Opportunities and challenges in additive manufacturing used in space sector: a comprehensive review. Rapid Prototyp. J., 28(10):2027–2042, 2022.

DOI: 10.1108/rpj-05-2022-0166

[2] Amir Malakizadi, Dinesh Mallipeddi, Sasan Dadbakhsh, Rachid M'Saoubi, and Peter Krajnik. Post-processing of additively manufactured metallic alloys – a review. International Journal of Machine Tools and Manufacture, 179:103908, aug 2022.

DOI: 10.1016/j.ijmachtools.2022.103908

[3] Kandice S.B. Ribeiro, Fábio E. Mariani, and Reginaldo T. Coelho. A study of different deposition strategies in direct energy deposition (DED) processes. Procedia Manufacturing, 48:663– 670, 2020.

DOI: 10.1016/j.promfg.2020.05.158

[4] Sadegh Rahmati and Ebrahim Vahabli. Evaluation of analytical modeling for improvement of surface roughness of FDM test part using measurement results. The International Journal of Advanced Manufacturing Technology, 79(5-8):823–829, feb 2015.

DOI: 10.1007/s00170-015-6879-7

[5] Amir Mostafaei, Amy M. Elliott, John E. Barnes, Fangzhou Li, Wenda Tan, Corson L. Cramer, Peeyush Nandwana, and Markus Chmielus. Binder jet 3d printing—process parameters, materials, properties, modeling, and challenges. Progress in Materials Science, 119:100707, jun 2021.

DOI: 10.1016/j.pmatsci.2020.100707

[6] L. Lebea, H. M. Ngwangwa, D. Desai, and F. Nemavhola. Experimental investigation into the effect of surface roughness and mechanical properties of 3d-printed titanium ti-64 ELI after heat treatment. International Journal of Mechanical and Materials Engineering, 16(1), nov 2021.

DOI: 10.20944/preprints202108.0477.v1

[7] C. Dordlofva, S. Brodin, and C. Andersson. Using demonstrator hardware to develop a future qualification logic for additive manufacturing parts. Proceedings of the International AstronauticalCongress, IAC, 7:25, 2019.

[8] A.B. Spierings, T.L. Starr, and K. Wegener. Fatigue performance of additive manufactured metallic parts. Rapid Prototyping Journal, 19(2):88–94, mar 2013.

DOI: 10.1108/13552541311302932

[9] Tejas Gundgire, Tuomas Jokiaho, Suvi Santa-aho, Timo Rautio, Antti Järvenpää, and Minnamari Vippola. Comparative study of additively manufactured and reference 316 l stainless steel samples – effect of severe shot peening on microstructure and residual stresses. Materials Characterization, 191:112162, sep 2022.

DOI: 10.1016/j.matchar.2022.112162

[10] Timo Rautio, Matias Jaskari, Tejas Gundgire, Terho Iso-Junno, Minnamari Vippola, and Antti Järvenpää. The effect of severe shot peening on fatigue life of laser powder bed fusion manufactured 316l stainless steel. Materials, 15(10):3517, may 2022.

DOI: 10.3390/ma15103517

[11] J.C. Outeiro. Residual stresses in machining. In Mechanics of Materials in Modern Manufacturing Methods and Processing Techniques, pages 297–360. Elsevier, 2020.

DOI: 10.1016/b978-0-12-818232-1.00011-4

[12] Usman Ali, Haniyeh Fayazfar, Farid Ahmed, and Ehsan Toyserkani. Internal surface roughness enhancement of parts made by laser powder-bed fusion additive manufacturing. Vacuum, 177:109314, jul 2020.

DOI: 10.1016/j.vacuum.2020.109314

[13] Pawan Tyagi, Tobias Goulet, Christopher Riso, Robert Stephenson, Nitt Chuenprateep, Justin Schlitzer, Cordell Benton, and Francisco Garcia-Moreno. Reducing the roughness of internal surface of an additive manufacturing produced 316 steel component by chempolishing and electropolishing. Additive Manufacturing, 25:32–38, jan 2019.

DOI: 10.1016/j.addma.2018.11.001

[14] Hiroshige Masuo, Yuzo Tanaka, Shotaro Morokoshi, Hajime Yagura, Tetsuya Uchida, Yasuhiro Yamamoto, and Yukitaka Murakami. Effects of defects, surface roughness and HIP on fatigue strength of ti-6al-4v manufactured by additive manufacturing. Procedia Structural Integrity, 7:19–26, 2017.

DOI: 10.1016/j.prostr.2017.11.055

[15] L. Denti, E. Bassoli, A. Gatto, E. Santecchia, and P. Mengucci. Fatigue life and microstructure of additive manufactured ti6al4v after different finishing processes. Materials Science and Engineering: A, 755:1–9, may 2019.

DOI: 10.1016/j.msea.2019.03.119

[16] Qu, Li, Fucai Zhang, and JiamingBai. Anisotropic cellular structure and texture microstructure of 316l stainless steel fabricated by selective laser melting via rotation scanning strategy. Materials & Design, page 110454, feb 2022.

DOI: 10.1016/j.matdes.2022.110454

[17] H. Gray, L. Wagner, and G. Lutjering. Influence of residual stresses on fatigue crack propagation of small surface cracks. DGM, 1987.

[18] Timo Rautio, Aappo Mustakangas, Jani Kumpula, and Antti Järvenpää. Scanning strategy effect on the edge porosity and fatigue life of 316l PBF-LB parts. Procedia CIRP, 111:130–133, 2022.

DOI: 10.1016/j.procir.2022.08.106