Novel Coating Technology Withstands Extreme Combustion Environments

The research effort began with a study to identify metals and coatings best suited for prolonged exposure to high heat and corrosive environments. Using advanced computational methods, including thermodynamic modeling, the team rapidly evaluated a wide range of candidate materials and narrowed the field to two promising formulas.

However, the ideal bulk metal identified through simulation was not available in the complex geometries required to make the internal structure of the Pulse Combustion Engine. To overcome this limitation, the team pivoted to engineered coatings, ultimately developing a custom NiCrAlY alloy solution that could be sprayed on the engine’s internal surfaces. The research showed that aluminum, particularly when combined with other strategic metals, was essential to achieving the coating’s resilience under thermal and chemical stress.

Even after identifying a viable coating formulation, the team faced a second major challenge: depositing the coating onto the interior surfaces of extremely narrow pipes — components that would be directly exposed to the system’s intense combustion process.

“One of the biggest challenges we faced in depositing this novel coating was getting it to adhere to a small inner diameter pipe,” said Ken Kane, a materials scientist at APL. “We had to develop a custom approach using a specialized plasma torch, which we’d never used before.”

For this task, the team built on insights gained from an internally funded research project that explored heat-resistant coating applications for hypersonic vehicle components. Team members systematically experimented with and refined the torch’s parameters, eventually identifying that the key to successful coating lay in selecting the appropriate powder morphology — an insight that enabled effective buildup of the coating despite the compact torch’s lower power output.

“This successful field test required a multidisciplinary approach and the ability to rapidly prototype, test, and refine under one roof,” said Cassidy Carroll, an APL analytical chemist and project manager. “APL’s unique mix of expertise, facilities, and strong partnerships with industry made it possible to move from concept through design iterations to full-system tests — and eventually to deliver a resilient technology designed to meet real-world challenges and support a safer, cleaner future.”