Worcester Polytechnic Institute (WPI), Worcester, Massachusetts, USA, has received a three-year, $25 million award from the U.S. Army Combat Capabilities Development Command Army Research Laboratory (CCDC-ARL) to develop cold spray Additive Manufacturing for use in the repair and production of metal parts.
WPI’s cold spray Additive Manufacturing process uses a pressurised gas to accelerate metal powders to near supersonic speeds. The force of impact causes the powders to adhere to the metal build surface. The institute explained that the process can be adapted to work with a portable handheld applicator, making it suitable for use in the military field.
“The army is interested in cold spray 3D printing as a repair technique,” stated Danielle Cote, assistant professor of materials science and engineering and director of WPI’s Center for Materials Processing Data, and the principal investigator for the ARL project. “It’s cheaper to repair a part than to replace it, and you get the equipment back in service faster.”
“The army’s primary interest is unit readiness,” she continued. “If you’re on a mission and need to move quickly to a safer place, and a critical part on your vehicle breaks, you’re stuck unless you can repair it quickly. That’s where cold spray comes in.”
WPI states that its primary research focus will include developing, characterising, and testing new alloys optimised for use in cold spray. Cote explained that the characteristics of the metal powders used in cold spray are important since the metal is not melted before being sprayed onto a part that needs repair, nor heat treated after application.
Cote added, “With most manufacturing methods, metal alloys are alerted by first being melted, and then often heat treated to strengthen or otherwise improve their properties. With cold spray, what you end up with in the repair is exactly what you start with, so the characteristics of the powders are quite important.”
As part of the research, the institute will reportedly use a variety of equipment, including instruments acquired as part of the new ARL award. These include tools to study the chemical and structural properties of the powders at the scale of nanometers, such as a SEM/EDS (Scanning Electron Microscope and Energy Dispersive Spectroscopy) unit, a synchronous laser diffraction and dynamic image particle analyser to determine powder morphologies, and nanoindenters to measure nano-scaled mechanical properties.
WPI’s research team plans to work with several subcontractors, including the University of California Irvine, the University of Massachusetts Lowell, Penn State University, and Solvus Global. Among the modifications that are expected to be made to the powders are unique thermal processing treatments, a technique WPI states that it pioneered.
Unlike metals used in other metal manufacturing processing, including casting and forging, the alloys used in cold spray do not have to be capable of being heat treated, which gives the WPI researchers access to a wide range of potential materials. However, the properties of cold spray powders can be fine-tuned with the careful application of heat.
Cote further added, “This expertise is part of the reason the ARL continues to support WPI. We have discovered that the properties of metal powders can be significantly enhanced with thermal processing, and that is what we are looking to do with this new award.”
As part of the research programme, a team of co-principal investigators from multiple disciplines at WPI will explore some new applications, including the use of cold spray to apply copper coatings to give equipment antibacterial properties. Researchers in WPI’s robotics engineering programme will explore the use of multi-axis robots to automate the cold spray process.
Cote continued, “The army is especially interested in portable cold spray systems, but the technology can also be used on a larger scale in industry, for example and it will be exciting to see how robots can help expand the use of this and other Additive Manufacturing processes.”
“I think there is much potential for this technique. With the work we will be doing with powder development, in robotics, and in a number of other areas, I think we are going to go a long way with cold spray. There really are endless possibilities,” she concluded.