Preparation of WC-Co cemented carbide by spark plasma sintering: Microstructure evolution, mechanical properties and densification mechanism

Abstract

In this study, Spark Plasma Sintering (SPS) was utilized to fabricate fine-grained cemented carbides, and an orthogonal experimental design was employed to examine the influence of holding temperature (1100 °C, 1200 °C, 1300 °C) and holding time (5, 10, and 15 min) on the performance of WC-10Co cemented carbide specimens. Compared with conventional sintering methods, this work achieved the production of samples with enhanced overall performance at lower temperatures and shorter durations. Specifically, under the conditions of a holding temperature of 1300 °C and a holding time of 5 min, the resulting specimens exhibited a density of 14.64 g/cm³, a hardness of 91.29 HRA, a fracture toughness of 16.39 MPa·m½, and a transverse rupture strength of 2398 MPa. The microstructural analysis revealed that as the holding temperature increased, the Co phase in the specimens underwent a transformation from its initial powder form to banded cobalt and subsequently to slit-shaped cobalt. It was found that the presence of banded cobalt effectively hinders crack propagation, whereas slit-shaped cobalt is more effective in preventing crack initiation, thus impacting the overall performance of the specimens. By analyzing the sintering curves and microstructures, the densification mechanisms during SPS sintering of WC-Co cemented carbides were elucidated. The study concluded that the state changes of the Co phase play a significant role in the densification behavior, final microstructure, and properties of the sintered material. These findings offer valuable insights for understanding and optimizing the SPS process.