Joining metals has, in some cases, posed many challenges. Examples of traditional techniques are soldering, welding, and riveting. Finding new, innovative ways to join and bond can make significant contributions to advancements in materials science.
“We have demonstrated that gaseous surface activation can enable metallurgical bonding, which is the first major leap in metal joining technology since the early 1990s,” says Filip Lenrick, Senior Lecturer, Production and Materials Engineering.
“This study introduces a new metal-joining method that we call Gas Actuated Bonding (GAB). The technique addresses key limitations of conventional joining processes. Unlike brazing, which depends on filler materials that may lead to corrosion and embrittlement, and unlike welding, which introduces high localized temperatures and stress gradients, GAB uses a gas to activate the metal surface and create direct metallurgical bonds. The process eliminates the need for filler materials while avoiding detrimental temperature gradients in the joined components.”
A method for delicate structures
These results open up new possibilities for joining things that are difficult to join today.
“With further development, we expect this method to be applicable to a wide range of joining challenges, including Micro-Electro-Mechanical Systems (MEMS), stents, complex geometries like honeycomb parts, and dissimilar material combinations such as titanium and steel.”
The method is based on Chemical Vapor Deposition (CVD) technology, and the researchers were worried that the gases would be deposited on the metal to be joined instead of reacting with the surface. Now, they have learned that it is possible to use this CVD technology for Chemical Vapor Transfer.
Penetrating the oxide layer
“Another thing we were concerned about was the stable chromium oxide (Cr₂O₃) layer on 316L stainless steel, which could act as a barrier. We now know that the active elements in CVD gases can penetrate this oxide layer. These elements continue to enrich the surface sufficiently to locally reduce the melting point. Understanding the underlying mechanism is an important topic for future research.”
PhD student Idil Yondu hopes that the results can be useful in demanding industries like aerospace, medicine, the energy sector, and sensor integration, by saving time and speeding up development.
“Industries like aerospace constantly develop new technologies, and GAB shortens the development time for joining new alloys and structures. GAB can be performed in one single furnace, which makes it very flexible for parameter changes, and optimization. As it is not the case with developing a new recipe in brazing, every iteration takes at least a month, whereas in GAB we are talking about hours,” Idil Yondu says.
From the abstract:
The Gas Actuated Bonding (GAB) is a novel joining method that employs gaseous melting-point-depressant (MPD) agents to induce a diffusion-active state at temperatures below the bulk melting point of the substrate metal. Using phosphine (PH3) as an MPD agent on stainless steel (316 L), we demonstrate that controlled MPD gas exposure followed by uniform heat treatment results in a metallurgical joint without the need for fillers, fluxes, or localized heat input. Microstructural and compositional analyses confirm phosphorus incorporation and diffusion at the interface, consistent with a joining mechanism driven by an interfacial layer capable of high mobility. This approach establishes a new framework for controllable, flexible metal joining.