The objective of the proposed study is to determine the feasibility of fully densifying a SiAlON via sinter/HIP processing. Sinter/HIP is an innovative approach to materials consolidation that incorporates sintering and containerless HIP'ing into a single, uninterrupted cycle conducted in a HIP system. In this proposed process technology, green preforms are sintered under moderate N2 pressure to high density and closed porosity in the HIP vessel; following completion of the designated sintering phase of the cycle, the vessel is rapidly pressurized to a suitable HIP'ing pressure (e.g., 30 KPSI), and the HIP phase of the cycle is then conducted. Sinter/HIP thus differs from the "conventional" concept of containerless HIP'ing, since sinter/HIP does not require or employ separate sintering and HIP'ing systems. Additionally, sinter/HIP makes possible processing conditions different from those used in the "conventional" sinter + containerless HIP approach. Thus sinter/HIP may yield technically unique materials with properties and niicrostructures unlike those produced via other process technologies. The proposed study will aini at fully densifying a 92 wtlr/o Si3N4 + 6 wtq/,o Y203 + 2 wtolo A1203 SiAlON via sinter/HIP. Room temperature niodulus of rupture (MOR) values for sinter/HIP'ed specimens will be generated and compared with MOR values for conipositionally similar sintered and sintered + containerless HIP'ed specimens.AnticipatedResults Potential Commercial Applications as described by the awardee:Containerless Sinter/HIP could be a cost-effective way of producing fully dense Si3N4 materials for use in an almost limitless variety of applications (turbine and other heat engine components; cutting tools; wear parts; arnior; etc.). It should be capable of high throughput (unlike uniaxial hot pressing and containerized HIP'ing) and of generating net or near-net shaped parts, which require little or no further machining.
