High Cycle Fatigue (HCF) Performance of Ti-6Al-4V Alloy Processed by Selective Laser Melting

Abstract:

Selective laser melting (SLM) is a relatively new additive manufacturing (AM) technology which uses laser energy for manufacturing in a layered pattern. The unique manufacturing process of SLM offers a competitive advantage in case of very complex and highly customized parts having quasi-static mechanical properties comparable to those of wrought materials. However, it is not currently being harnessed in dynamic applications due to the lack of reliable fatigue data. The manufacturing process shows competitive advantages particularly in the aerospace and medical industry in which Ti-6Al-4V is commonly used, especially for high performance and dynamic applications. Therefore, in this exploratory research, high cycle fatigue (HCF) tests were performed for as-built, polished and shot-peened samples to investigate the capability of SLM for these applications. As-built samples showed a drastic decrement of fatigue limit due to poor surface quality (R_a ≈ 13 µm) obtained from the SLM process. Polishing improved the fatigue limit to more than 500 MPa, the typical value for base material. The effect of shot-peening proved to be antithetical to the expected results. In this context, fractographic analysis showed that very small remnant porosity (less than 0.4%) played a critical role in fatigue performance.

• Periodical: Advanced Materials Research (Volumes 816-817)
• Pages: 134-139
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.816-817.134
• Online since: September 2013
• Authors: Eric Wycisk, Claus Emmelmann, Shafaqat Siddique, Frank Walther
• Keywords: Crack Initiation, Fatigue Limit, High Cycle Fatigue (HCF), Selective Laser Melting (SLM), Ti-6Al-4V, Titanium Alloy

References

[1] D. Thomas: The development of design rules for selective laser melting. University of Wales, Cardiff (2010).

[2] Q. Bo, H. Fei, S. Yu-sheng, W. Qing-song: Comparison of two scan strategies applied to selective laser melting. International Conference on Computer Application and System Modeling (2010) 685-689.

DOI: 10.1109/iccasm.2010.5619227

[3] E. Santos, F. Abe, Y. Kitamura, K. Osakada, M. Shiomi: Microstructure and mechanical properties of pure titanium models fabricated by selective laser melting. Journal of Mechanical Engineering Science 218 (2004) 711-719.

DOI: 10.1243/0954406041319545

[4] J.P. Kruth, M. Bodrossamay, E. Yasa, J. Deckers, L. Thijs, J. Van Hmbeeck: Part and material properties in selective laser melting of metals. 16th International Symposium on Electromachining (2010).

[5] E. Wycisk, J. Kranz, C. Emmelmann: Fatigue strength of light weight structures produced by laser additive manufacturing in TiAl6V4. Proceedings of 1st International Conference of the International Journal of Structural Integrity, Porto (2012).

[6] C. Casavola, S.L. Campanelli, C. Pappaletteri: Experimental analysis of residual stresses in the selective laser melting process. Proceedings of the XIth International Congress and Exposition, Florida (2008).

[7] P. Mercelis, J-P. Kruth: Residual stresses in selective laser sintering and selective laser melting. Rapid Prototyping Journal, 12, 5 (2006) 254-265.

DOI: 10.1108/13552540610707013

[8] L. Wagner, G. Luetjering: Influence of shot peening on the fatigue behavior of titanium alloys. First International Conference on Shot Peening (1981) 453-460.