It makes sense that the defense supply chain is widely responsible for the steady advances being recorded by developers of additive manufacturing technologies, particularly those systems involving precision alloy materials. Defense-oriented objectives often have access to the brightest minds in engineering and design, as well as to funding sources that are committed to technology breakthroughs.

Elmet Technologies, the only U.S.-owned and operated, fully integrated manufacturer of high-performance tungsten and molybdenum products, recently adopted 3D Systems’ DMP Flex 350 Triple laser powder bed fusion, metal additive machine, for rapid production of aerospace parts for hypersonic vehicles.

Using a high-performance C103 material, Elmet expects to rapidly qualify and certify the system to begin production this year.

Emerging technology

Hypersonic propulsion is an area of particular emphasis for the U.S. Dept. of Defense and the aerospace technology developers at work in its orbit. Hypersonic missiles are an emerging class of weapons technology intended to operate at low altitudes (subspace) and travel at Mach 5 (five times the speed of sound) or greater; the combination of speed, low altitude, and maneuverability make them highly effective at avoiding detection by radar or missile defense systems.

Laser powder bed fusion (LPBF) is an additive manufacturing process for printing metal components, using a high-powered laser to selectively melt and fuse fine material powder, layer by layer, as informed by a CAD model of the part.

High-performance material

Niobium C103 is a high-performance, heat-resistant refractory metal alloy comprised of niobium (~89%), hafnium (~10%), and titanium (~1%). It is engineered specifically for extreme applications in which more standard metals like steel, titanium, or nickel-based superalloys would melt or lose structural integrity.

As explained by developer, Elmet Technologies has spent the past eight years working with 3D Systems’ engineers to develop processing parameters for C103 material, specifically for this application.

“We collaborated with 3D Systems’ Application Innovation Group (AIG) on the parameter sets for the C103 material,” explained Elmet R&D manager Scott Ohm. “The work was done on an earlier 3D Systems metal 3D printer and we expect that prior research work will make it very easy to begin production on the DMP 350 Flex Triple.”

Rare operating conditions

The DMP Flex 350 Triple supports a 350x350x350-mm build size, applying lasers to the metal powder to increase productivity. A controlled-atmosphere environment maintains <25 ppm oxygen, typically ~0-6 ppm oxygen. These low oxygen (and other interstitial element) conditions allow for exceptional powder reuse rates along with tight control of metal chemistry and superior surface finishes, according to 3D Systems.

Elmet Technologies intends to use this system to produce large heat exchangers for hypersonic vehicles. Reportedly, it selected this particular metal 3D printer for several reasons:

• Very low oxygen content maintained within the system promote very high-quality, consistent, and repeatable parts production using refractory metals
• The larger build size helps to meet the rising performance and quality standards of customers in this manufacturing sector
• The three-laser system makes it possible to produce parts in high volumes, quickly
• It works well with Elmet’s novel in-house materials
• It is anticipated to enable fast qualification and certification

“This machine, material and process should achieve qualification within a couple of months,” Ohm stated. “We anticipate NASA 6030 certification a few months after that. This is very fast and indicative of the quality of this entire solution, as well as confirmation of the sound business case for collaboration 3D Systems’ Aerospace and Defense experts to streamline the qualification and certification process.”

DMP for monolithic parts

3D Systems’ metal printing technology converts high-performance, heat-transfer structure designs into manufactured parts that are accurate, complex, and leak tight, with less assembly, shorter lead times, reduced costs, higher yield, and better reliability than conventional, standard processes like brazing. Using Direct Metal Printing (DMP) reduces reliance on extended supply chains and helps protect intellectual property - and it allows Elmet to deliver components that cannot be produced using the standard methods. This means parts with complex features, thin walls, increased surface-to-volume ratios, and maximal heat transfer with acceptable pressure drop.

“This collaboration with Elmet is a standout example of using metal additive manufacturing to create new advantages in aerospace design and production,” stated Mike Shepard, 3D Systems v.p. of Aerospace & Defense. “The low oxygen architecture of our DMP series metal additive machines is ideal for manufacture of complex components from highly reactive metals, like C103 and other refractory alloys.”