Graphite creep negation during flash spark plasma sintering under temperatures close to 2000 C

Graphite creep has high importance for applications using high pressures (100 MPa) and temperatures close to 2000 degrees C. In particular, the new flash spark plasma sintering process (FSPS) is highly sensitive to graphite creep when applied to ultra-high temperature materials such as silicon carbide. In this flash process taking only a few seconds, the graphite tooling reaches temperatures higher than 2000 degrees C resulting in its irreversible deformation. The graphite tooling creep prevents the flash spark plasma sintering process from progressing further. In this study, a finite element model is used to determine FSPS tooling temperatures. In this context, we explore the graphite creep onset for temperatures above 2000 degrees C and for high pressures. Knowing the graphite high temperature limit, we modify the FSPS process so that the sintering occurs outside the graphite creep range of temperatures/pressures. 95% dense silicon carbide compacts are obtained in about 30 s using the optimized FSPS. (c) 2020 Elsevier Ltd. All rights reserved.