CERAMIC MOLD-HIP PROCESSING OF NB-AL INTERMETALLIC POWDER

The Nb3Al is one of the futuristic high temperature structural materia ls, but is poor in plastic workability. Therefore, the Ceramic Mold-HI P process is noteworthy toward powder metallurgical process for shape- making, and is as follows: The Nb3Al powders are filled up in a cerami c mold prepared by lost wax process, which is set in secondary pressin g media enclosed with a metal can, and HIPed under high temperature pr essure. Y2O3 ceramic and Y2O3/CaO mixture were mainly used as less rea ctive ceramic mold for the Nb3Al powders during HIPing, and as the sec ondary pressing media, respectively. The Nb-25.2at%Al powders in the c eramic mold were consolidated into the tentative forms of cone, blade and tube under the HIP condition of 1573K/196MPa. The Nb-22.8/25.2at%A l powder compacts obtained showed lower compressive strength in as-HIP ed state. However, when held above 1873K to remove prior particle boun dary (PPB) by grain growth, they had almost 3 times compressive streng th compared to as-HIPed one (ex. over 100 MPa at 1773K). Furthermore, the Nb3Al-base composites with 10 wt% of ceramic fines such as Y2O3 an d ZrO2 were elucidated to have a potential for the improvement of high temperature strength.