As the military modernizes to prepare for a next-generation fight with peer or near-peer adversaries, the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory (CCDC-ARL) contributes by developing groundbreaking innovations in 3-D printing that dramatically expand what capabilities can be delivered to the warfighter.
Making use of new innovations in laser technology, materials science, and design software, the laboratory is developing the ability to 3-D print large components out of ultra-high strength steel and perhaps even high-strength, lightweight alloys like aluminum and magnesium.
“Most of our work in 3-D printing to date has been using the technology to accelerate developmental programs through rapid prototyping,” Dr. Brandon McWilliams, an ARL researcher told us in a recent interview.
This initiative, however, goes beyond what is typically possible when one thinks of 3-D printing. Not only is the Army Research Laboratory printing large metal components, which alone is a challenging task for additive manufacturing, but they are using that technology to produce metals that are as much as 50% stronger than the same material when forged or cast because of differences in the metals at the molecular level.
It doesn’t take much imagination to begin to see the possibilities that open up if the Army can print armor and components from ultra-high strength metals that can also be efficiently produced in far more complex shapes than before. Nor is it difficult to see how this could make a difference for the Soldier on the tactical edge.
To get more details about the technology, what makes it possible, and to learn more about the use cases that ARL envisions for it, read on below for our full interview with Dr. McWilliams:
GDH: Why is 3-D printing large steel components a natural evolution for the Army? What benefits will it deliver to Soldiers in the field?
Brandon McWilliams: The Army uses a lot of big, heavy, metal parts since all equipment has to be ruggedized for the field, and because metal printing has been evolving over time to larger and larger production scales, getting to the point of applying the technology to this use makes a lot of sense.
GDH: What has been a limiting factor for this kind of manufacturing in the past?
Brandon McWilliams: One of the big limitations that kept us from exploiting the technology for the Soldier has been the scale of parts that can be made, particularly with powder bed fusion.
This technique has been limited in the past because the equipment used a single laser, which means it takes a very long time to make a large part even if it were physically possible.
The cost of lasers has decreased radically in the last few years meaning that it is more practical for new machines to incorporate multiple high-power lasers to speed up the process. This requires advancements in process controls to sync multiple lasers moving at very high speeds, like one to two meters per second, as well as innovation to minimize the amount of powder feedstock required to print and minimize wasted material.
Advanced process monitoring sensors and data analytics are also required to enable qualification of these large additive manufacturing components.
GDH: Why is steel a more challenging medium for 3-D printing large components than polymers and what are some ways that you and your team plan to address these technical challenges?
Brandon McWilliams: Metal printing in general typically requires much higher temperatures than printing polymers, and the most popular method to print metals is to use high power lasers, which requires much more electrical power than your common filament polymer systems. Metal powders can also pose safety and health risks that need to be mitigated in order to print safely.
GDH: There are claims that this manufacturing technique could produce steel that is significantly stronger than if it were made using conventional means. Why is this the case?
Brandon McWilliams: Laser-based printing of metals creates very rapid heating and cooling which results in huge thermal gradients within a part. These thermal gradients can cause negative effects, like residual stresses that cause the part to distort or fail prematurely, often causing build failures.
However, these thermal gradients can also be manipulated by materials scientists for positive benefits if we understand the process well enough to optimize the process parameters to locally control the microstructure.
For example, in certain cases microstructural features such as the grain size and amount of retained austenite phase of a steel can be controlled through the thermal gradients resulting in improvements in properties compared to conventionally manufactured equivalents.
GDH: What are some of the use cases for this technology? What types of products or parts do you envision this being used to create?
Brandon McWilliams: We envision using this technology to print complex geometry components for next generation munitions as well as next generation combat materials. Hard materials, such as armor steel, are very difficult to manufacture into complex shapes, which is why most legacy combat vehicles, and structures on/within them, resemble a box and are not streamlined at all. You are essentially limited to what you can create by welding together plates, or paying a premium to machine these hard materials.
By printing these hard materials, it opens up the design space to reduce weight, reduce manufacturing costs, and increase performance of these systems.
GDH: What role is digital design software playing in these initiatives? How are these solutions making the design and fabrication of these products and parts possible?
Brandon McWilliams: Design software plays a critical role. Our design team, led by Dr. Andrew Gaynor, is developing advanced topological optimization algorithms that account for manufacturing constraints and material microstructure to create multi-objective designs that are lighter weight and higher performance than the components we could traditionally design and manufacture.
GDH: Lastly, since this project is still in its early stages, what developments can we expect to see from you and your team in the short term, and thinking long term, when will we see these products and parts deployed in the field?
Brandon McWilliams: In the short term we are focused on feedstock alloy development for ultra-high strength steel alloys as well as lightweight alloys such as high strength aluminum and magnesium. I think we can expect to see metal parts produced by additive manufacturing deployed in the field in the next couple years.
To learn more about all of the CCDC Army Research Laboratory’s work on advanced manufacturing, click HERE.
Featured image, provided by CCDC Army Research Laboratory, shows a sample piece of ultra-high strength steel alloy created using powder bed fusion.
