Gas actuated bonding: a novel metal joining method with melting point depressant gases

Metal joining remains an essential yet challenging process in manufacturing, particularly for components with small dimensions, multiplex, delicate geometries, or dissimilar metals, where conventional joining methods can be insufficient. Here, we introduce Gas Actuated Bonding (GAB), 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.