Investigation of the heating rate influence on the processes of TiB₂—TiN nanocomposite spark-plasma synthesis

Abstract

The dependences of shrinkage, phase composition, mechanical properties, microstructure characteristics on temperature and heating rate under reactionary SPS synthesis of 20—80% TiB₂—TiN composition at temperatures of 900—1700 °C at heating rates v = 100—2360 K/min were researched. The increase in the heating rate of the sample before reaching the exposure promotes the preservation of the nano- and fine-grained structure due to the decrease in the time interval of the embryos growth phase during the TiB₂ formation. The high heating rate (v = 1890—2360 K/min), rapid intermediate cooling (v = 2125 K/min) and subsequent annealing at a sufficiently low temperature (T = 1400 °C) resulted in a composition with very high microhardness values (HV₁₀₀ = 31,2—40,2 GPa) and sufficient values of crack resistance (K_1c = 5,8— 6,5 MPa∙m^1/2).