"EVALUATION OF EROSION RESISTANCE IN A SIMULATED FBC ENVIRONMENT OF COATINGS APPLIED USING A HYPERSONIC SPRAY PROCESS"

IT HAS BEEN DEMONSTRATED THAT COATINGS DEPOSITED BY A RECENTLY-DEVELOPED PROCESS CALLED THE HYPERSONIC FLAME SPRAY PROCESS ARE HARDER, DENSER, AND LESS POROUS THAN COATINGS APPLIED BY PLASMA SPRAY OR CONVENTIONAL FLAME SPRAYTECHNIQUES. AS SUCH, THIS PROCESS HAS THE POTENTIAL TO APPLY COATINGS ONTO THE SURFACE OF FBC SUPERHEATER TUBES WHICH ARE MUCH MORE RESISTANT TO EROSION THAN EXISTING COATINGS. SUCH A DEVELOPMENT WOULD RESULT IN REDUCED FBC MAINTENANCE COSTS AND IMPROVED RELIABILITY AND OPERABILITY. THIS PROPOSAL OUTLINES A PROGRAM TO SYSTEMATICALLY EVALUATE THE EROSION/CORROSION RESISTANCE OF A NUMBER OF COMPOSITIONSAPPLIED BY THE HYPERSONIC FLAME SPRAY PROCESS, USING THE SIMULATED FBC EROSION TEST RIG AT THE LAWRENCE BERKELEY LABORATORY TO SCREEN THE APPLIED COATINGS. THE COATINGS FORTHE MOST PART WILL BE MECHANICALLY-BLENDED MIXTURES OF A HARD CARBIDE AND A SOFTER, CORROSION-RESISTANT MATRIX ALLOY. THE CARBIDES WHICH WILL BE CONSIDERED ARE WC, CR3C2, TIC, AND NBC, AND THE MATRIX CONSTITUENTS WILL BE FECRALY, NICRMO, AND COCR. WE WILL COMPARE THE EROSION/CORROSION RESISTANCE OF THESE TO A NUMBER OF UNCOATED TUBE ALLOYS AND TO SOME CONVENTIONAL COATINGS, INCLUDING CERAMIC COATINGS AND NITRIDED AND CHROMIZED COATINGS. WE PLAN IN ADDITION TO EVALUATE AT LEAST TWO TYPES OF A NEW CLASS OF ALLOYS KNOWN AS AMORPHOUS METALS. THESE MATERIALS HAVE DEMONSTRATED SUPERIOR EROSION/CORROSION RESISTANCE, ANDTHERE ARE INDICATIONS THAT THEIR APPLICATION USING HYPERSONIC SPRAY ALLEVIATES THE REVERSION TO CRYSTALLINITY WHICH HAS PLAGUED THEIR APPLICATION BY PLASMA SPRAY.