J-B. Hwang
S-WELDING, South Korea
Keywords: SWaP-Critical Aerospace Systems, Ultra-Slim Consumer Electronics, Dual-Use Thermal Infrastructure
We develop diffusion-bonded metal structures for mission-critical thermal systems. The technology originated from high-temperature heat exchanger development for advanced nuclear systems, including very-high-temperature reactors (VHTRs) and small modular reactors (SMRs), where diffusion-bonded PCHEs were considered for intermediate heat exchangers and steam generators.A key challenge in diffusion bonding of heat-resistant alloys for such applications is the formation of secondary interfacial phases—such as carbides or oxides—when local solubility limits (Ksp) are exceeded by the reaction quotient (Q). These precipitates disrupt metallurgical continuity and compromise long-term mechanical performance. To address this, we apply surface alloying as a pre-treatment to locally modify the chemical composition near the bonding surface. This shifts interfacial equilibrium conditions, suppressing the precipitation of secondary phases and promoting stable metal-to-metal diffusion bonding. The result is a structurally coherent joint with improved creep and fatigue resistance, operable beyond 600°C. This method has been experimentally validated in diffusion bonding of Ni-based and Fe-based superalloys, producing joints with mechanical integrity aligned with nuclear-grade benchmarks. By focusing on interfacial chemistry over geometric design, we deliver compact, high-reliability bonded structures fit for aerospace, energy, and defense systems—where thermal performance and structural continuity are critical./