Researchers adapt U.S. Air Force-developed steel alloy for metal AM
March 14, 2019
Army researcher Dr Brandon McWilliams holds a sample part created from AF96 powder at the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory (Courtesy U.S. Army / David McNally)
Researchers at the U.S. Army Combat Capabilities Development Command (CCDC)’s Army Research Laboratory, Aberdeen Proving Ground, Maryland, USA, have adapted AF96, a steel alloy originally developed by the U.S. Air Force, to powder form for use in Powder Bed Fusion (PBF) Additive Manufacturing processes.
The researchers report that this steel alloy has outstanding qualities and, more importantly, potential applications for ground vehicle replacement parts. Dr Brandon McWilliams, a team lead in the lab’s manufacturing science and technology branch, stated, “This material that we’ve just printed and developed processing perimeters for is probably about 50% stronger than anything commercially available.”
For Army applications, the key to the powder alloy’s usage will be to certify whether additively manufactured AF96 parts will work as needed in a battlefield scenario. “We’ve printed some impeller fans for the M1 Abrams [Main Battle Tank] turbine engine and we can deliver that part – they can use it, and it works,” stated McWilliams. “But it’s not a qualified part.”
“In terms of a battlefield scenario that may be good enough to be able to get your tank running again for hours or days if that’s important to the mission,” he continued, “but on the other hand, we still need to be able to answer, does this perform as good as the OEM part? Does this perform better?”
The researchers highlighted two strategies for the alloy’s use moving forward. Firstly, metal AM can be used to produce parts in AF96 for battlefield sustainment, i.e. the replacement of existing parts and supporting legacy systems.
Secondly, the researchers hope to work with the metal Additive Manufacturing industry on further applications and systems using the powder. “That’s where we’re more integrated with the OEMs and industry to see the things they’re working on and see how we can make things better to really push the state-of-the-art,” McWilliams stated.
The Air Force initially developed AF96 for application in ‘bunker-busting bombs’ – bombs of high enough strength and hardness to penetrate hardened targets. For this purpose, a metal was needed that was very high-strength and high-hardness, but which remained economical.
“The nice thing about that for the Army is that it has wide-ranging applications,” McWilliams explained. “We have interest from the ground combat vehicle community, so it could be used for replacement parts. A lot of our parts in ground vehicles now are steel. So this could be dropped in as a replacement not having to worry about material properties because you know it’s going to be better.”
The laboratory is now said to be working closely with industry and academic researchers to model new alloy designs, perform computational thermodynamics and expedite the process to get the materials to soldiers. “We’ve developed a road map and that’s an integrated plan that’s now focused on supporting our modernisation priorities, but we’re also tied closely to the ground combat vehicle community,” McWilliams concluded.
