Fabrication of Dense, Near Net-Shaped W/ZrC Composites by the PRIMA-DCP Process

The fundamental conversion mechanism for the following net liquid/solid displacement reaction has been examined: (Zr) + WC(s) =ZrC(s)+W(s) (1) where (Zr) refers to zirconium dissolved within a Zr-Cu melt. Such mechanistic knowledge is needed in order to be able to predict the time required, under various processing conditions, for full conversion of porous WC performs into dense ZrC/W composites (e.g., for rocket nozzle applications) by the DCP method. For this fundamental study, dense wafer of WC were prepared by hot isostatic pressing at 1850 degrees C. The wafers were then immersed in a vertical orientation in a Zr-Cu melt at temperatures in the range of 115O-1400 degrees C for times up to 24 hours. After such exposure, the polished WC surfaces were found to be coated with two reaction product layers. A layer of tungsten was observed to be in direct contact with the WC. A second, external layer of ZrC separated the W layer from the melt.