PSI - Issue 17

Thomas Simson et al. / Procedia Structural Integrity 17 (2019) 843–849 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

849

7

4. Conclusion

The results demonstrated that the high-strength MAR 300 which was comparable to the wrought material could be produced by LPBF and subsequent solution annealing heat treatments. The mechanical properties of the solution annealed samples were observably improved by applying aging treatment at 490 ºC for 6 hours. (1) The investigations on the steel powders in the fresh state and after multiple use show a strong increase in their oxygen content during operation whereas the sieving for multiple use does not change particle size distributions and morphology remarkably. (2) The hardness, tensile strengths as well as ductility of solution annealed and aged samples reached standard wrought level. After aging, the hardness increased from 333~341 HV10 to 640~656 HV10. The ultimate tensile strength ( Rm ) increases from 1056~1096 MPa to 1964~2102 MPa, while the break elongation ( ε tot ) was reduced from 11.3~16.0% to 2.0~4.5%. This indicated that the strength was well enhanced while the ductility was seriously reduced due to the formation of intermetallic precipitates. Notch impact tests show a significant decrease in toughness for the aged samples. This is also shown by the impact tests at low temperatures (-20 °C and -50 °C). (3) The ball joint test setup has shown that the frame manufactured by LPBF provides comparable results as a conventionally manufactured frame and is therefore robust and suitable for the prototype and test production of car headlamps. The results showed that the MAR 300, which was comparable to wrought material, can be produced by the LPBF with subsequent solution annealing and aging.

Acknowledgements

This study was financially supported by the Bavarian State Ministry for Finances via the BTHA within the research cooperation, “New materials in the additive manufacturing” which is gratefully acknowledged.

References

Rüßmann, M.; Lorenz, M.; Gerbert, P.; Waldner, M.; Justus, J.; Engel, P.; Harnisch, M. Industry 4.0: The Future of Productivity and Growth in Manufacturing Industries; Boston Consulting Group: Boston, MA, USA, 2015; Volume 9. German, R.M. Particle Packing Characteristics; Metal Powder Industries Federation: Princeton, NJ, USA, 1989. Olakanmi, E. Selective laser sintering/melting (SLS/SLM) of pure Al, Al-Mg, and Al-Si powders: Effect of processing conditions and powder properties. J. Mater. Process. Technol. 2013, 213, 1387 – 1405. Rombouts , M. Selective laser sintering/melting of iron-based powder. PhD thesis KULeuven (2006). Yasa, E., Deckers, J., Kruth, J. P., Rombouts, M., & Luyten, J. (2009, September). Experimental investigation of Charpy impact tests on metallic SLM parts. In

4th International Conference on Advanced Research in Virtual and Rapid Prototyping, Leiria, Portugal (Vol. 7). Brandon, D., and Kaplan, W. D. (2013). Microstructural characterization of materials. John Wiley & Sons. ASTM Standard, E8/E8M-2013a, Standard Test Methods for Tension Test of Metallic Materials, ASTM International, 2013. ASTM, E 23-96, Standard Test Methods for Notched Bar Impact Testing of Metallic Materials.

Tewari R, Mazumder S, Batra I S, Dey G K and Banerjee S (2000), ‘Precipitation in 18 wt% Ni maraging steel of grade 350’, Acta Mater, 48, 1187– 200. Kempen, K., Yasa, E., Thijs, L., Kruth, J. P., & Van Humbeeck, J. (2011). Microstructure and mechanical properties of Selective Laser Melted 18Ni-300 steel. Physics Procedia, 12, 255-263.