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. 2024 Sep 16;17(18):4548.
doi: 10.3390/ma17184548.

Effects of Process Parameters and Process Defects on the Flexural Fatigue Life of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion

Brandon Ramirez  1   2 , Cristian Banuelos  1   2 , Alex De La Cruz  1   2 , Shadman Tahsin Nabil  1   2 , Edel Arrieta  1   2 , Lawrence E Murr  2 , Ryan B Wicker  1   2 , Francisco Medina  1   2
Affiliations

Effects of Process Parameters and Process Defects on the Flexural Fatigue Life of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion

Brandon Ramirez et al. Materials (Basel). .

Abstract

The fatigue performance of laser powder bed fusion-fabricated Ti-6Al-4V alloy was investigated using four-point bending testing. Specifically, the effects of keyhole and lack-of-fusion porosities along with various surface roughness parameters, were evaluated in the context of pore circularity and size using 2D optical metallography. Surface roughness of Sa = 15 to 7 microns was examined by SEM, and the corresponding fatigue performance was found to vary by 102 cycles to failure. The S-N curves for the various defects were also correlated with process window examination in laser beam power-velocity (P-V) space. Basquin's stress-life relation was well fitted to the experimental S-N curves for various process parameters except keyhole porosity, indicating reduced importance for LPBF-fabricated Ti-6Al-4V alloy components.

Keywords: Basquin’s law fitting; Ti-6Al-4V alloy; additive manufacturing; fatigue performance; laser powder bed fusion; porosity defects; surface roughness.

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Conflict of interest statement

The authors declare they have no competing or financial interests or personal relationships that could have influenced the research reported herein.

Figures

Figure 1
Figure 1
Comparison of the four-point bending and the three-point bending moment diagrams.
Figure 2
Figure 2
Process parameters selected for printing (orange).
Figure 3
Figure 3
Print orientation of the tested samples (in the center) printed at randomly assigned process parameters.
Figure 4
Figure 4
Scanning strategies used for each process parameter.
Figure 5
Figure 5
Scanning strategies used for each parameter.
Figure 6
Figure 6
4-point bending fatigue test setup.
Figure 7
Figure 7
Ti-6Al-4V printed with keyholing parameters 370 W and 800 mm/s, 99.62% Dense. Taken using a Keyence VHX-7000.
Figure 8
Figure 8
Ti-6Al-4V printed EOS Nominal Parameters. The parameters are 280 W and 1200 mm/s, 99.99% Dense. Taken using a Keyence VHX-7000.
Figure 9
Figure 9
Ti-6Al-4V printed with lack of fusion parameters 370 W and 2000 mm/s, 99.79% Dense. Taken using a Keyence VHX-7000.
Figure 10
Figure 10
SEM surface comparison between EOS nominal (NOM) and EOS nominal improved.
Figure 11
Figure 11
Fatigue peak stress vs. number of cycles to failure curves.
Figure 12
Figure 12
Basquin’s law fit of the S–N curves in Figure 11 (colored lines).
See this image and copyright information in PMC

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