INNOVATIVE MULTILAYER METALLIC COATINGS ON SIC FIBERS VIA NOVEL CHEMICAL VAPOR DEPOSITION TECHNIQUES FOR TIAL MATRIX COMPOSITES

DARPA IS SEEKING RESEARCH AIMED AT ADDRESSING THIN UNIFORM COATING OF MULTIFILAMENT TOWS OF CERAMIC AND/OR GRAPHITE FIBERS AT ECONOMICALLY ATTRACTIVE RATES. THESE FIBERS WILL BE USED FOR COMPOSITES BASED ON CERAMICS, TITANIUM ALLOYS AND TITANIUM ALUMINIDE MATRICES. WE PROPOSE TO DEVELOP MULTILAYERED, ENGINEERED INTERFACE COATINGS FOR SIC FIBERS COMPATIBLE WITH TIAL INTERMETALLIC MATRIX. FIRST APPROPRIATE METALLIC COATINGS WILL BE IDENTIFIED WHICH WILL MAKE THE SIC FIBERS 1) CHEMICALLY COMPATIBLE, 2) MATCH ITS COEFFICIENT OF THERMAL EXPANSION WITH TIAL MATRIX, 3) IMPART HIGH INTERFACIAL BOND STRENGTH, AND 4) IMPART LOCAL DUCTILITY AT THE INTERFACE. THESE COATINGS WILL THEN BE DEPOSITED ON MULTIFILAMENT TOWS OF SIC FIBERS USING INNOVATIVE CHEMICAL VAPOR DEPOSITION (CVD) TECHNIQUES THAT HAVE THE POTENTIAL TO INCREASE DEPOSITION KINETICS AND IMPROVE COATING ECONOMICS. THESE NEW CVD TECHNIQUES COMBINE THE LOW COST OF PACK METALLIZATION WITH THE HIGH HEAT AND MASS TRANSFER OF A FLUIDIZED BED REACTOR. THE MORPHOLOGY, THICKNESS, MICROSTRUCTURE AND COMPOSITION OF THE COATINGS, AS WELL AS THE EXTENT OF DIFFUSION AND REACTION BETWEEN THE SIC FIBER AND THE COATINGS WILL BE CHARACTERIZED. WE PROPOSE TO FORM A TEAM WITH PROF. AMIT GHOSH, UNIVERSITY OF MICHIGAN, TO DESIGN MULTI-LAYERED COATINGS, AND DR. ANGEL SANJURJO, SRI INTERNATIONAL TO DEPOSIT THE COATINGS VIA CVD TECHNIQUES, TO COMPLIMENT MARKO'S EFFORT WHICH HAS PROCESSED HIGH QUALITY RAPIDLY SOLIDIFIED (MELT SPUN) TIAL POWDERS SUITABLE FOR FABRICATION OF SIC/TIAL COMPOSITES.