A NOVEL PROCESSING-MICROSTRUCTURAL DESIGN APPROACH TO FORM RELIABLE CERAMIC MATRIX COMPOSITES

THE CERAMIC-REINFORCED CERAMIC-MATRIX COMPOSITES (CMCS) OFFER SIGNIFICANT ADVANTAGES OF FRACTURE TOUGHNESS AND HIGH TEMPERATURE STRENGTH OVER THE MONOLITHIC CERAMICS. HOWEVER, MICROSTRUCTURAL DESIGN COUPLED WITH CONTROLLED PROCESSING IS REQUIRED TO FORM RELIABLE MATERIALS THAT CAN BE SAFELY APPLIED FOR INDUSTRIAL APPLICATIONS. A NOVEL PROCESSING APPROACH IS PROPOSED FOR FABRICATING DENSE, NEAR-NET SHAPE SIC WHISKER REINFORCED SI3N4 COMPOSITES. IT INVOLVES REDUCING FLAWS ORIGINATING FROM PROCESSING AND SIMULTANEOUSLY INTRODUCING TOUGHENING MECHANISMS. HIGH PRESSURE, QUASI-ISOSTATIC LOWER TEMPERATURE CONSOLIDATION WILL BE EMPLOYED TO FORM A BSI3N4 MATRIX WITH TUNGSTEN COATED SIC WHISKERS TO THEORETICAL DENSITIES WHILE MAINTAINING A FINE MATRIX GRAIN SIZE, MINIMIZING INTERFACIAL REACTIONS AND OBTAINING OPTIMIZED DEBONDING. SUCCESSFUL COMPLETION OF PHASE I WILL RESULT IN DEMONSTRATION OF A PROCESS FOR FABRICATING RELIABLE CMCS WITH PROPERTIES SUPERIOR TO THE STATE-OF-THE-ART. PHASE II WILL INTEGRATE THE WHISKERS IN 2-D COUPLED WITH FIBER ROUGHENING IN THE 3-D STRUCTURE. PHASE II WILL DEMONSTRATE NEAR-NET SHAPE CAPABILITY AND FABRICATION OF A STRUCTURAL PROTOTYPE. PHASE III WILL SCALE UP THIS PROCESS ESTABLISHING A MANUFACTURING CAPABILITY FOR FORMING RELIABLE, HIGH TOUGHNESS, HIGH STRENGTH, CERAMIC MATRIX COMPOSITES. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - THE DEVELOPMENT OF THIS PROPOSED APPROACH TO FORM RELIABLE CERAMIC-MATRIX COMPOSITES WILL ENABLE ACCELERATED APPLICATION OF CERAMICS IN HIGH TEMPERATURE APPLICATIONS IN DOD. SIGNIFICANT ACTIVITIES IN THE USE OF CERAMIC MATERIALS IN THE AIR FORCE, ARMY, AND NAVY WILL BENEFIT. COMMERCIAL SPIN-OFFS ARE LIKELY IN ADVANCED CUTTING TOOLS, TURBOEHOGERS, BEARINGS AND WEAR PARTS.