Tribological properties of ZrN–Si₃N₄-TiN composites consolidated by spark plasma sintering

Abstract

The production of ZrN-Si₃N₄ and ZrN–Si₃N₄–TiN composites by spark plasma sintering and the mechanical and tribological properties of the consolidated materials were studied. The densification of the ZrN–Si₃N₄–TiN composites was found to proceed more intensively in the range 1100-1300 °С, and nanocrystalline titanium nitride was the main factor that stimulated the densification of these composites. Ceramic 57 wt.% ZrN–43 wt.% Si₃N₄ and 84 wt.% ZrN–16 wt.% Si₃N₄ samples with a relative density of 0.95 and 0.93 and (84 wt.% ZrN–16 wt.% Si₃N₄)–15 wt.% TiN and (57 wt.% ZrN–43 wt.% Si₃N₄)–30 wt.% TiN composites with a relative density of ~0.98 were produced. Microstructural studies showed that the consolidated ZrN–Si₃N₄ composites had a uniform distribution of the components over the material with an average grain size of 200–300 nm. The ZrN–Si₃N₄–TiN composites had a finer structure with TiN grains smaller than 100 nm. The mechanical properties of the titanium nitride composites were higher than those of the ZrN–Si₃N₄ materials. Thus, the Vickers hardness and fracture toughness of the composites containing 15 and 30 wt.% TiN determined by indentation were 18.7 ± 1.1 GPa and 5.2 MPa · m^1/2 and 19.1 ± 1.9 GPa and 5.8 MPa · m^1/2, respectively. The hardness of the ZrN-Si₃N₄ composites was ~17 GPa. The tribological properties of the composites were tested with the VK6 hardmetal and silicon nitride. The wear resistance of the ceramic samples directly depended on the contents of zirconium nitride and counterface, i.e., on their physicochemical interaction. When the ZrN content increased to 84%, the tribological properties of the composite increased substantially through the lubricating capability of zirconium nitride. The (84 wt.% ZrN–16 wt.% Si₃N₄)–15 wt.% TiN composite showed the best tribological properties and can be recommended for use in friction units under dynamic loads.