Spark plasma sintered ZrC-Mo cermets: Influence of temperature and compaction pressure

Abstract

The microstructure analysis and mechanical characterisation were performed on a ZrC-20wt%Mo cermet that was spark plasma sintered at various temperatures ranging between 1600 and 2100°C under either 50 or 100MPa of compaction pressure. The composite reached ~98% relative density for all experiments with an average grain size between 1 and 3.5µm after densification. The nature of SPS technology caused a faster densification rate when higher compaction pressures were applied. The difference in compaction pressures produced different behaviors in densification and grain structure: 1900°C, 100MPa produced excessive grain growth in ZrC; 1600°C, 50MPa revealed a very clear ZrC grain structure and Mo diffusion between carbide grains; and 2100°C, 50MPa exhibited the highest overall mechanical properties due to small clusters of Mo phases across the microstructure. In fact, this particular sintering regime gave the most optimal mechanical values: 2231 HV10 and 5.4MPa*m1/2, and 396GPa Young's modulus. The compaction pressure of SPS played a pivotal role in the composites’ properties. A moderate 50MPa pressure caused all three mechanical properties to increase with increasing sintering temperature. Conversely, a higher 100MPa pressure caused fracture toughness and Young modulus to decrease with increasing sintering temperature.