A GENERIC CHEMICAL PROCESSING TECHNOLOGY FOR THE PRODUCTION OF NANOSTRUCTURED COMPOSITE MATERIALS

SPRAY CONVERSION PROCESSING (SCP) IS A NEW CHEMICAL PROCESSING TECHNOLOGY CAPABLE OF PRODUCING BULK QUANTITIES OF NANOSTRUCTURED COMPOSITE POWDERS, STARTING FROM WATER SOLUBLE PRECURSORS. THE TECHNOLOGY HAS CONSIDERABLE VERSATILITY, BUT IS UNABLE TO DEAL WITH REACTIVE ELEMENTS SUCH AS ALUMINUM (A1), SILICON (SI), TITANIUM (TI), VANADIUM (V), NIOBIUM (NB), AND TANTALUM (TA), WHICH FORM THERMODYNAMICALLY STABLE OXIDES THAT CANNOT EASILY BE REDUCED TO THE METALLIC STATE. TO OVERCOME THIS DEFICIENCY, THIS PROJECT IS STUDYING THE INCORPORATION OF CHEMICAL VAPOR INFILTRATION (CVI) OF REACTIVE ELEMENTS AS A FINAL STEP IN THE SCP OF HIGH SURFACE AREA (NANOPOROUS) POWDERS. THE NEW INTEGRATED SCP+CVI TECHNOLOGY SHOULD ENABLE A WIDE VARIETY OF NANOSTRUCTURED COMPOSITE MATERIALS TO BE PRODUCED, WHICH WILL EXTEND THE RANGE OF POTENTIAL APPLICATIONS. NANOSTRUCTURED TUNGSTEN CARBIDE-COBALT (WC-CO) POWDERS WITH 30 TO 50 NM WC GRAIN SIZE HAVE BEEN PRODUCED SUCCESSFULLY BY SCP. HOWEVER, DURING CONSOLIDATION BY LIQUID-PHASE SINTERING, THE WC GRAIN SIZE RAPIDLY COARSENS TO ABOUT 200 TO 300 NM, EVEN AFTER A SHORT TIME (5 MIN) AT THE PEAK SINTERING TEMPERATURE (1,400 DEGREES CENTIGRADE). THE PRIMARY OBJECTIVE OF THIS RESEARCH IS TO ACHIEVE A FURTHER REDUCTION IN WC GRAIN SIZE IN THE FULLY CONSOLIDATED MATERIAL BY MAKING USE OF A KNOWN GRAIN GROWTH INHIBITOR, VANADIUM CARBIDE (VC). NANOSTRUCTURED WC-CO MATERIALS WITH <50 NM WC GRAIN SIZE SHOULD EXHIBIT SUPERIOR HARDNESS AND WEAR PROPERTIES. THUS, SUCH MATERIALS CAN POTENTIALLY REVOLUTIONIZE THE HARDFACING, CUTTING TOOL, DRILL BIT, AND WEAR PART INDUSTRIES. THE OBJECTIVES OF THE PHASE I PROJECT ARE (1) TO INTRODUCE VC INTO NANOSTRUCTURED WC-CO POWDERS BY CVI, (2) TO DEMONSTRATE REDUCED WC GRAIN SIZE IN VC-DOPED MATERIAL AFTER LIQUID-PHASE SINTERING, AND (3) TO DETERMINE THE DEGREE OF HARDNESS IMPROVEMENT ATTRIBUTED TO REDUCED WC GRAIN SIZE. THIS RESEARCH WILL LAY THE FOUNDATION FOR INTEGRATING SCP TECHNOLOGY WITH CVI TO PRODUCE BULK QUANTITIES OF VC-DOPED POWDERS FOR SUBSEQUENT CONSOLIDATION INTO PROTOTYPE TOOLS AND WEAR PARTS.