Spark plasma sintering of pure TiCN: Densification mechanism, grain growth and mechanical properties

This study aims to disclose the densification mechanism and grain growth behaviors during the spark plasma sintering (SPS) of undoped TiCN powder. The SPS experiments were performed under temperatures ranging from 1600 °C to 2200 °C and a fixed pressure of 50 MPa. The sintering mechanisms were described in different models according to two grain growth behaviors: densification without grain growth at low temperatures (1600-1700 °C) and grain growth without apparent densification at higher temperatures (1800-2200 °C). At the constant grain stage, a creep model is applied to describe the densification process. In addition, the effective stress exponents, n, are calculated, indicating that the densification can be attributed to both grain boundary sliding (n = 1.5) and dislocation climbing (n = 3.13 or n = 4.29). During the second stage of sintering, the grain growth model reveals that the grain-growth is controlled by grain boundary diffusion. In addition, the Vickers hardness varies from 4326 Hv to 6762 Hv when the density ranges from 90% to 96.3%.