On the role of melt flow into the surface structure and porosity development during selective laser melting

By C. Qiu, Chinnapat Panwisawas, M. Ward, Hector Basoalto, J. Brooks, Moataz M. Attallah. 2015

933 citations recorded by the source corpus.

Abstract In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied and correlated with the melt flow behaviour through both experimental and modelling approaches. The as-fabricated samples were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The interaction between laser beam and powder particles was studied by both high speed imaging observation and computational fluid dynamics (CFD) calculation. It was found that at a high laser power and a fixed powder layer thickness (20 μm), the samples contain particularly low porosity when the laser scanning speeds are below 2700 mm/s. Further increase of scanning speed led to increase of porosity but not significantly. The porosity is even more sensitive to powder layer thickness with the use of thick powder layers (above 40 μm) leading to significant porosity. The increase of porosity with laser scanning speed and powder layer thickness is not inconsistent with the observed increase in surface roughness complicated by increasingly irregular-shaped laser scanned tracks and an increased number of discontinuity and cave-like pores on the top surfaces. The formation of pores and development of rough surfaces were found by both high speed imaging and modelling, to be strongly associated with unstable melt flow and splashing of molten material.

Subfields: Computational Mechanics, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/b9a1454bb3538a481102a5d7fd56ba755eee8551

How researchers see this paper

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In Computational Mechanics

1. Wayne E. King
2. S. Khairallah
3. P. Peyre
4. D. Gu
5. A. Rubenchik
6. A. Anderson
7. O. Desmaison
8. R. Fabbro

In Mechanical Engineering

1. T. DebRoy
2. T. Mukherjee
3. H. Wei
4. Amitava De
5. D. Gu
6. Wei Zhang
7. J. Elmer
8. N. Gao

Citations in the corpus

• Metal additive-manufacturing process and residual stress modeling (2016, background): “showed that the recoil pressure is a possible explanation for the sparks observed during powder bed processes [39].”
• Corrosion performance of additively manufactured stainless steel parts: A review (2020, background): “choosing a smaller powder layer thickness extends the production time which should be taken into account [251,252].”
• Experimental analysis of spatter generation and melt-pool behavior during the powder bed laser beam melting process (2018, background): “However, a significant part of metal ejections either contaminate the powder bed surface or directly fall on the as-built metal, thus promoting metallurgical defects on final parts as indicated by Qiu et al. (2015) on Ti-6Al-4V titanium alloy and Liu et al. (2015) on 316L stainless steel.”
• Fluid and particle dynamics in laser powder bed fusion (2018, methodology): “[2] undertook a systematic study of the effect of laser scan speed and powder layer thickness on porosity using a commercial Concept Laser M2 system.”
• Selective laser melting of Invar 36: Microstructure and properties (2016, background): “Unstable melt pool tends to lift up material away from the build surfaces rather than spread steadily along laser scanning direction [10], which is liable for development of cave-like pores (Fig.”