3D Printing

New 3D printing technique fuses titanium particles at supersonic speeds

New 3D printing technique fuse...
A microscope image of titanium alloy particles produced using the team's new "cold spray" 3D printing technique. Biological cells have begun to adhere to it, showing its usefulness in biomedical implants.
A microscope image of titanium alloy particles produced using the team's new "cold spray" 3D printing technique. Biological cells have begun to adhere to it, showing its usefulness in biomedical implants.
View 1 Image
A microscope image of titanium alloy particles produced using the team's new "cold spray" 3D printing technique. Biological cells have begun to adhere to it, showing its usefulness in biomedical implants.
1/1
A microscope image of titanium alloy particles produced using the team's new "cold spray" 3D printing technique. Biological cells have begun to adhere to it, showing its usefulness in biomedical implants.

Engineers at Cornell University have developed a new technique for 3D printing metallic objects – and it involves blasting titanium particles at supersonic speeds. The resulting metals are very porous, which makes them particularly useful for biomedical objects like implants and replacement joints.

Traditional 3D printing involves a nozzle depositing plastic, hydrogels, living cells or other materials layer by layer to build up an object. Metal parts and objects are usually 3D printed in other ways, such as firing a laser at a bed of metal powder to selectively melt sections into the desired shape, or firing metal powder at high speeds at a substrate to fuse the particles together.

The latter method is known as “cold spray,” and the new technique expands on that base. The Cornell team blasted titanium alloy particles, each measuring between 45 and 106 microns wide, at speeds up to 600 m (1,969 ft) per second (for reference, the speed of sound in air is around 340 m (1,115 ft) per second). The team calculated this as the ideal speed – any faster, and the particles would disintegrate too much on impact to bond to each other.

Next the materials are heated to soften them, helping the particles bond better. Again this is carefully controlled, using temperatures of up to 900 °C (1,652 °F), which is well below titanium’s melting point of 1,626 °C (2,959 °F).

The end result is a metallic object with a porous structure that can be up to 42 percent stronger than similar objects made using conventional manufacturing processes. The difference, the team says, is that the new method doesn’t focus on high heat as the primary force, which can introduce weaknesses to the material.

“We focused on making cellular structures, which have lots of applications in thermal management, energy absorption and biomedicine,” says Atieh Moridi, lead author of the study. “Instead of using only heat as the input or the driving force for bonding, we are now using plastic deformation to bond these powder particles together.”

The researchers say the new method is particularly well-suited to creating biomedical implants because the porous structure would give patients' cells somewhere to cling to, helping rebuild the natural tissue and anchor the implant.

“If we make implants with these kind of porous structures, and we insert them in the body, the bone can grow inside these pores and make a biological fixation,” says Moridi. “This helps reduce the likelihood of the implant loosening. And this is a big deal. There are lots of revision surgeries that patients have to go through to remove the implant just because it’s loose and it causes a lot of pain.”

The team says that the new method could also create materials and objects for other industries, such as construction, transportation and energy.

The research was published in the journal Applied Materials Today.

Source: Cornell University

4 comments
paul314
A lot of powdered metals will sinter at temperatures well below their melting points. You need vacuum or some kind of inert gas to make the process work, because a lot of powdered metals burn really well. I wonder if this could be applied to other than titanium. (Also potentially a tool for fabrication in orbit.)
Moc
Cold Spray has been an additive technology for decades now (academia and industry) and the research into Ti has been ongoing since the early 2010s. I love the technology and cannot wait to see where it ends up within the industry, but this article is very misleading in the discovery of the actually technique and the pioneers who have improved the technology to where it is today. If people are interested in would love to learn more I would encourage them to look into the research performed by universities such as North Eastern, South Dakota School of Mines, or Worcester Polytechnic.
Techrex
?? If this amazing, 3D printed porous Titanium is going to be used for bone implants ( I see you, WOLVERINE!) , and because it is a metal element, and all metals conduct electricity, would installing a temporary wiring to these special implants in the bones of such patients, enable us to pass a very low-power electrical current or grounding through the Titanium implants, that would greatly speed up the patient's bones adhesion or bonding with this material? Cut down on his healing up time?
bahbah
Bravo Atieh Moridi
May I suggest the following? Use hollow cylinders instead of solid spheres; try Ti fibres; print in a vacuum; use lasers for heating at point of impact; after the printing process, use high amp current to fuse the particles together at their points of contact; partial oxidation of the final product or partial coating with magnesium/ calcium/ phosphate for better bio bonding.