LASER BRAZING PROCESS DEVELOPMENT FOR CERAMIC-TO-METAL JOINING OF RADOME COMPONENTS

THERE IS A NEED FOR UNIQUE JOING/BONDING PROCESSES THAT CAN DIRECTLY JOIN CERAMIC IR AND RF DOME COMPONENTS TO CYLINDRICAL METAL SURFACES. EXPOSURE TO THE HIGH TEMPERATURES ASSOCIATED WITH CONVENTIONAL BRAZING PROCESSES CAN DEGRADE THE OPTICAL PROPERTIES OF MATERIALS AND PROMOTE CHEMICAL REACTION BETWEEN THE BRAZE MATERIAL AND THE CERAMIC THROUGHOUT THE ENTIRE HEAT AFFECTED ZONE (HAZ). THEREFORE, IT IS DESIRABLE TO UTILIZE A HIGHLY LOCALIZED HEAT SOURCE FOR THE JOINING EFFORT. THIS PROPOSAL SUGGESTS LASER BRAZING AS A MEANS OF PROVIDING THE HEAT NECESSARY TO FORM A METALLURGICAL BOND WHILE LIMITING THE THERMAL DEGRADATION TO REGIONS ADJACENT TO THE JOINT. INNOVATIVE GLASS CERAMIC MATERIALS HAVING MATCHED COEFFICIENTS OF THERMAL EXPANSION WILL BE USED AS BRAZE FILLER. THE PHASE I TECHNICAL OBJECTIVE INCLUDE EVALUATION OF CANDIDATE BRAZING MATERIALS, DESIGN OF A LASER PROCESSING CHAMBER, SELECTION OF LASER PROCESSING PARAMETERS, ACQUISITION OF FAMILIES OF TEST DATA AND OPTIMIZATION OF A PROOF-OF-CONCEPT SYSTEM FOR ENGINEERING DEVELOPMENT IN PHASE II OF THE PROGRAM. SUCCESSFUL COMPLETION OF THE PROGRAM OBJECTIVES WOULD RESULT IN A TECHNIQUE FOR PRODUCING HERMETICALLY SEALED CERAMIC-TO-METAL JOINTS HAVING GOOD THERMALMECHANICAL PROPERTIES AND MINIMAL HAZ.