Spray conversion processing (SCP) is a new chemicalprocessing technology capable of producing bulk quantities ofnanostructured composite powders, starting from water solubleprecursors. The technology has considerable versatility, but isunable to deal with reactive elements such as aluminum (Al),silicon (Si), titanium (Ti), vanadium (V), niobium (Nb), andtantalum (Ta), which form thermodynamically stable oxides thatcannot easily be reduced to the metallic state. To overcome thisdeficiency, this project is studying the incorporation of chemicalvapor infiltration (CVI) of reactive elements as a final step inthe SCP of high surface area (nanoporous) powders. The newintegrated SCP+CVI technology should enable a wide variety ofnanostructured composite materials to be produced, which willextend the range of potential applications. Nanostructuredtungsten carbide cobalt (WC-Co) powders with 30 to 50 nm WC grainsize have been produced successfully by SCP. However, duringconsolidation by liquid-phase sintering, the WC grain size rapidlycoarsens to about 200 to 300 nm, even after a short time (5 min) atthe peak sintering temperature (1,400'C). The primary objective ofthis research is to achieve a further reduction in WC grain size inthe fully consolidated material by making use of a known graingrowth inhibitor, vanadium carbide (VC). Nanostructured WC-Comaterials with <50 nm WC grain size should exhibit superiorhardness and wear properties. Thus, such materials can potentiallyrevolutionize the hardfacing, cutting tool, drill bit, and wearpart industries. The objectives of the Phase I project are (1) tointroduce Vu into nanostructured WC-Co powders by CVI, (2) todemonstrate reduced WC grain size in VC-doped material afterliquid-phase sintering, and (3) to determine the degree of hardnessimprovement attributed to reduced WC grain size. This researchwill lay the foundation for integrating SCP technology with CVI toproduce bulk quantities of VC-doped powders for subsequentconsolidation into prototype tools and wear parts.Anticipated Results/Potential Commercial Applications as described by the awardee:The manufacture of drill bits, cutting tools, wearparts, hardfacing, punch and die sets, extrusion dies, nozzles, andvalve seats and liners could be benefited in a major way.
