Sandia National Laboratories has extensive programs in welding and brazing that support basic research, develop-ment, and production. We also conduct joint R&D with many university and industrial partners. Our award-wining R&D programs emphasize a comprehensive physical understanding of processing/microstructure/proper-ties/performance relationships, combined with practical experience gained from many years of defense production. For example, to meet stringent requirements for small-lot production of high-consequence weapon components or satellite hardware, while reducing costs, we have a strong effort to assure that our manufacturing processes are so well understood and controlled that we can simplify or eliminate many quality assurance inspections.
High-reliability laser welding requires that the last weld be identical to the first.
Sandia offers extensive experimental, prototyping, testing, and modeling capabilities in welding and brazing. These capabilities include specialized materials testing and process-diagnostics equipment, as well as custom and commercial software for desktop PC through supercomputer analysis, design, and modeling.
Sandia-developed desktop software helps welding engineers rapidly optimize weld procedures.
Welding: The compatibility of materials to be joined is of paramount importance. Poor post-weld mechanical properties and fusion-zone defects, such as solidification cracking and porosity, often can be avoided by conducting a thorough weldability analysis early in the product design process. Expertise in solidification science, solid-state transformation kinetics, and microstructural evolution enables Sandia to specify the optimum engineering alloys for a specific welding application.
Computer codes that predict thermal and fluid-flow responses during furnace brazing are improving furnace throughput and product yields.
Another area of emphasis is hermetic welding of small, high-precision components via laser, resistance, and arc welding. Effective thermal and stress management is essential in such applications. We combine novel experimental tools with advanced computational modeling to understand heat source/weldment/fixturing interactions, thermal transients, and how they affect residual stress.
High-temperature, thermal-mechanical test.
Brazing: Brazing is an enabling technology for next-generation, metal-ceramic joints for hermetic military and commercial electro-mechanical devices. Applications include heat engines, thermal batteries, high-voltage tubes, microwave components, and similar structural assembles with insulator-metal joints.
Physical and mechanical properties must be precisely known to accurately predict brazing responses. Special facilities are used to determine selected properties of braze alloys, including microstructural and elevated temperature properties. Sandia is developing an extensive properties database to support constitutive models. For example, elevated temperature creep properties over a range of test temperatures have been used to predict stresses in hermetic metal-ceramic, high-voltage tube assemblies.
Sandia recently initiated a comprehensive effort to incorporate the fundamental physics of braze materials and processes into different thermal, fluid flow, and structural models to predict macro- and micro-responses during brazing. The use of massively parallel computing permits very detailed solutions to complex brazing problems.