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Research Papers

Simulating Melt Pool Shape and Lack of Fusion Porosity for Selective Laser Melting of Cobalt Chromium Components

[+] Author and Article Information
Chong Teng

3DSIM,
LLC,
Park City, UT 84098
e-mail: chong.teng@3dsim.com

Haijun Gong

Visiting Assistant Professor,
Georgia Southern University,
Statesboro, GA 30460

Attila Szabo

GE Power & Water,
Greenville, SC 29615

J. J. S. Dilip, Shanshan Zhang

University of Louisville,
Louisville, KY 40292

Katy Ashby, Brent Stucker

3DSIM,
LLC,
Park City, UT 84098

Nachiket Patil

3DSIM,
LLC,
Park City, UT 84098,

Deepankar Pal

3DSIM,
LLC,
Park City, UT 84098;
University of Louisville,
Louisville, KY 40292,

Manuscript received January 6, 2016; final manuscript received June 14, 2016; published online August 10, 2016. Assoc. Editor: Y. B. Guo.

J. Manuf. Sci. Eng 139(1), 011009 (Aug 10, 2016) (11 pages) Paper No: MANU-16-1011; doi: 10.1115/1.4034137 History: Received January 06, 2016; Revised June 14, 2016

Cobalt chromium is widely used to make medical implants and wind turbine, engine and aircraft components because of its high wear and corrosion resistance. The ability to process geometrically complex components is an area of intense interest to enable shifting from traditional manufacturing techniques to additive manufacturing (AM). The major reason for using AM is to ease design modification and optimization since AM machines can directly apply the changes from an updated STL file to print a geometrically complex object. Quality assurance for AM fabricated parts is recognized as a critical limitation of AM processes. In selective laser melting (SLM), layer by layer melting and remelting can lead to porosity defects caused by lack of fusion, balling, and keyhole collapse. Machine process parameter optimization becomes a very important task and is usually accomplished by producing a large amount of experimental coupons with different combinations of process parameters such as laser power, speed, hatch spacing, and powder layer thickness. In order to save the cost and time of these experimental trial and error methods, many researchers have attempted to simulate defect formation in SLM. Many physics-based assumptions must be made to model these processes, and thus, all the models are limited in some aspects. In the present work, we investigated single bead melt pool shapes for SLM of CoCr to tune the physics assumptions and then, applied to the model to predict bulk lack of fusion porosity within the finished parts. The simulation results were compared and validated against experimental results and show a high degree of correlation.

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References

Figures

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Fig. 1

Melt pool width and depth measurement for a 310 W, 850 mm/s single bead scan

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Fig. 2

Melt pool profiles of single bead scans on one layer of powder with different laser power and speed combinations at 200 × (50 μm scale)

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Fig. 3

Surface plot of melt pool width from experimental measurement

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Fig. 4

Surface plot of melt pool depth from experimental measurement

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Fig. 5

Top surface topology of 10 mm × 10 mm × 10 mm porosity cubes at 100 × (100 μm scale)

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Fig. 6

Porosity cube sectioning and mounting schematic

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Fig. 7

Melt pool width (simulation versus experiment)

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Fig. 8

Melt pool depth (simulation versus experiment)

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Fig. 9

Cross-sectional melt pool comparison from simulation versus experiment for a 310 W, 850 mm/s single bead scan (dashed line exhibits the melt pool contour predicted via simulation)

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Fig. 10

A schematic plot of porosity data mining in simulation

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Fig. 11

Porosity comparison at 310 W (simulation versus experiment)

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Fig. 12

Porosity comparison at 335 W (simulation versus experiment)

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Fig. 13

Porosity comparison at 360 W (simulation versus experiment)

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Fig. 14

Porosity comparison at 385 W (simulation versus experiment)

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