150W) were investigated for brazing process. Different Laser Systems including CO2 (10.6 micrometers, 1kW), ND:YAG (1.06 micrometers, 4kW). Thin section iron base superalloy A286 tube was used as substrate materials. Gold (Au-Cu-Ni-Pd-Mn) based high temperature braze alloys were used in both powder and wire form. The objective of this study was to develop a laser brazing process to provide quality, localized braze joints without adverse affect on the parent materials. Poor braze quality or damage to the parent materials limits the nozzle service life. Being the only manned flight reusable rocket engine, it has stringent requirement on the braze process. Localized braze processes were considered to eliminate braze voids, however, damage to the parent materials often prohibited use of such process. The nozzle can be disqualified for flight or result in mission failure if the braze voids exceed the limits. Braze voids between coolant tubes may result in hot combustion gas escape causing jacket bulges. SSME nozzle experiences extremely high heat flux (180 mW/sq m) during hot fire. Subsequent furnace braze cycles are performed due to localized braze voids between the coolant tubes. The Space Shuttle Main Engine (SSME) consists of 1080 conical tubes, which are furnace brazed themselves, manifolds, and surrounding structural jacket making almost four miles of braze joints.
Laser Brazing of High Temperature Braze Alloy