Abstract
In this study, TiN–TiB2–hBN composite ceramics were prepared via reactive hot pressing using TiN and amorphous B powders as raw materials. Different sintering temperatures and composition ratios were studied. The results show that the 70 vol% TiN–17.6 vol% TiB2–12.4 vol% hBN ceramic composites obtained ideal comprehensive properties at 1600 °C. The relative density, Vickers hardness, bending strength, and fracture toughness were 99%, 11 GPa, 521 MPa, and 4.22 MPa·m1/2, respectively. Densification was promoted by the highly active reaction product TiB2, and the structural defects formed in the grains. Meanwhile, the good interfacial bonding between TiN and TiB2 grains and the uniform dispersion of ultrafine hBN in the matrix contributed to the excellent bending strength. Moreover, the toughening mechanism of crack deflection and grain pull-out improved the fracture toughness.
Highlights
TiN gets a lot of attention owing to its excellent properties
Considering the above factors, in this study, TiN–TiB2–hexagonal boron nitride (hBN) composite ceramics were fabricated by TiN–B reaction sintering, and their microstructure and mechanical properties were explored
The furnace was heated to 1400 ◦C at 20 ◦C/min in vacuum, and after dwelling for 0.25 h to remove the volatile impurities, we continued to raise the temperature at 10 ◦C/min to the sintering temperature in an argon atmosphere
Summary
TiN gets a lot of attention owing to its excellent properties. As a high hardness and refractory nitride compound of group IVB transition metal, TiN has a hardness of 18 GPa and a melting point of 2950 ◦C [1,2]. TiN–TiB2 composite ceramics have a good application prospect in the fields of wear parts, aircraft engine components, cutters, and armors. It has good prospects for molten salt electrolysis and high-performance power systems [11]. The strong covalent bonds of transition metal nitrides and borides contribute to a high melting point and low self-diffusion coefficient, making the densification of monolithic TiN and TiB2 very difficult [12,13,14]. Studies have shown that, in hard refractory carbides, nitrides, and borides, the presence of hexagonal boron nitride or graphite with layered structures can significantly enhance the machining property and thermal stability [18,19,20,21]. Considering the above factors, in this study, TiN–TiB2–hBN composite ceramics were fabricated by TiN–B reaction sintering, and their microstructure and mechanical properties were explored
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