b'P ROVING THE P RINCIPLEImproved Iron-Based Alloys from therefore, lower inertia, lower cost of raw materi- Vision System for High LuminosityNoble Gas Doping1988 als, and conservation of possibly strategic and/or Processes1986Research Team:John E. Flinn critical materials in some applications. Structural Research Team:Jon Bolstad, M.B. Ward, C.L.ceramics are, however, difficult to form in either Shulllarger size parts or in complex geometriesD e s c r i p t i o n The primary function of this product :is to strengthen alloys for high-temperature appli- because the forming process usually requires D e s c r i p t i o n :This system produces high-qualitycations. Noble gas atoms (e.g., those of helium or some combination of high temperature and high video imagery of industrial or experimentalar gon), when entrapped during the processing of pressure. Some method of joining the ceramics processes which are normally obscured by highiron-base powders, stabilize the microstructure while maintaining the structural integrity and luminosity of an electric arc, a plasma, or a com-and strengthen the alloy produced. The alloying thermodynamic qualities of the ceramic is needed bustion flame. It has particular application inaddition forms numerous small and very stable to produce the larger and/or more complex shapes electric arc welding where detailed vision of theclusters with vacancies (missing atom sites) dur- required in many applications. The oxynitride welding pool, electrode, and liquid/solid interfaceing rapid cooling. The formation of the clusters is braze method for joining silicon nitride ceramics is required. The welding site is illuminated bydue to the high binding energy between the noble presented here has been demonstrated to be an pulsed laser light transported to the welding torchgas atoms and the vacancies that are created by e ffective joining technique using either a hot iso- by one or more optical fibers. The sensor assem-high temperature exposure (i.e., heat treating). static press or a graphite resistance furnace with bly incorporates objective optics, a laser line fil-Because they retard microstructure coarsening, the small nitrogen overpressure. In this process, te , a microchannel plate image intensifier tube, rclusters allow fine microstructures to be retained oxynitride glass brazes are used to join silicon and a CCD video camera. The intensifier tube isduring exposure to high temperatures. Cluster nitride ceramics. The glass uses are comparable shuttered electronically in synchronism with thepresence provides a form of solid solution and in composition to the grain boundary phase pre- flash from the laser source, which occurs onlydispersion strengthening. The strengthening is fur- sent in the ceramic pieces that results from the once per video frame (or some multiple thereof).ther enhanced during aging heat treatments densification process used to consolidate the sili- The shuttering interval (about 100 nanoseconds)because the clusters provide nucleation, or pre- con nitride powders.is very small in comparison with the 33 millisec-ferred, sites for the formation of precipitates such Die-Target for Dynamic ond integration time of a standard video camera.as carbides. The fine dispersion of a large number Consolidation of Powders1987 The welding arc light is almost totally eliminatedof precipitates significantly improves the strength from the video picture. Visibility through the arcof the alloy. This process is applicable to all iron- Research Team:John E. Flinn, Gary E. Korth is regained, and extreme variation in brightnessbase alloys, particularly to stainless steels. D e s c r i p t i o n Die T: ar get for Dynamic across the picture is removed. The video imageryOxynitride Braze Method for Joining Consolidation of Powders is a new and improved is much superior to standard video for interpreta-Silicon Nitride Ceramics1988 method of consolidating metal monoliths from tion by eye and by electronic image processingeqrapidly solidified powders (RSP). The Die-Targetui p m e n t .Research Team:R.M. Neilson, D.N. Coon, S.T. Scheutz, R.L. Tallman controls dynamic stress waves produced by deto-nation of explosive charges to consolidate RSPD e s c r i p t i o n :Structural ceramics are potential alloys.With each detonation, the Die-Tar get pro-substitutes for strategic and/or critical materials. duced four fully consolidated, fully dense, crack-H o wefree monoliths for test specimens.This processve r, many potential structural ceramicapplications require components that are too intri- does not produce high generalized temperaturescate or too large to be fabricated with existing in the powders, which could seriously alter thetechniques. The invention is a method for joining microstructure and desirable properties for thesilicon nitride ceramics to produce large partsRSP. Monoliths produced by the dynamic consol-and/or parts that have complex geometries in idation of RSPalloys (e.g., stainless steel) havewhich the high-temperature mechanical properties improved mechanical properties, improved corro-of the joined part are comparable to that of the sion resistance, chemical homogeneity, extendedoriginal ceramic components. For certain applica- solubility limits, very fine microstructures, andtions (e.g., aerospace, engines, chemical process- desirable metastable phases. At present, the pri-ing) ceramic parts, and complex shapes are mary use of the Die-Tar get is as a research tool.Hopreferred to metals. Reasons include: increased w e ve r, the theory and principles underlyingservice operating temperatures, greater strength the design hold promise for industrial and com-and increased corrosion resistance at the higher mercial applications of the DIE-Ta rget wheretemperatures, greater thermodynamic effici e ncadvanced materials that are harder and strongeryin energy conversion devices, lower density and, are needed.28 0'