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In a recently published paper, scientists from Carnegie Mellon University and Argonne National Laboratory used high-speed x-ray imaging to study the keyhole effect in powder-based metal 3D printing.
A keyhole is a subcategory of void, or pore, that can sometimes be found in AM components.
Anthony - Rollett - Co-author - Paper - Professor
Anthony Rollett, a co-author of the paper and Professor of Materials Science and Engineering at Carnegie Mellon University, said, “The research in this paper will translate into better quality control and better control of working with the machines.”
“FOR ADDITIVE MANUFACTURING TO REALLY TAKE OFF FOR THE MAJORITY OF COMPANIES, WE NEED TO IMPROVE THE CONSISTENCY OF THE FINISHED PRODUCTS. THIS RESEARCH IS A MAJOR STEP IN THAT DIRECTION.”
PBF - Laser - Metal - Powder - Pool
In PBF, when a laser hits the metal powder it forms a melt pool. This melt pool expands due to heat and then cools down to form a solid layer. If the laser power is too high, the evaporation rate and melt pool temperature also increase. Due to this, the melt pool penetrates into the layer forming a ‘keyhole’ pore. The keyhole can lead to cracking and the general weakness of the part.
The understanding of what happens to the metal powder when it is hit by a laser is still limited. The recent paper, which used Ti-6Al-4V powder as a sample, hopes to advance our understanding of keyholes pores in metal 3D printing.
Science - Problem - Laser - Cang - Zhao
“We are really studying a very basic science problem, which is what happens to metal when you heat it up with a high-power laser,” commented Cang Zhao, a post-doc at Argonne National Laboratory and co-author of the research.
“BECAUSE OF OUR UNIQUE EXPERIMENTAL CAPABILITY, WE ARE ABLE TO WORK WITH OUR COLLABORATORS ON EXPERIMENTS THAT ARE REALLY VALUABLE TO MANUFACTURERS.”
Depth - Pores - Intensities - Laser - Power
The depth of keyhole pores measured at varying intensities of laser power. Image via Science.
Synchrotron imaging is a non-destructive analysis...
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