Физико-механические свойства керамики на основе Si3N4 различной дисперсности с 3 масс. % Y2O3 – Al2O3

Abstract

This article focuses on the process of producing ceramics based on the commercial Si3N4 powder of the various dispersions (< 5 μm and < 1 μm) by spark plasma sintering (SPS). The powder mixtures of 97 wt. % Si3N4 + 3 wt. % additives of the Y2O3 – Al2O3 composition were synthesized by the Pechini method. The SPS technology was used to obtain the ceramic samples of ∅ 20 mm. Sintering was carried out in a vacuum at the heating rate of 50 °C/min and the load of 70 MPa until the shrinkage end. The microstructure and the phase composition of the ceramic samples were investigated. Mechanical properties were measured: Vickers hardness, Palmquist fracture toughness, flexural strength according to the B3B (Ballon-Three-Balls-Test) method. Tribological tests were also carried out. It was established that the lower the dispersion of the powder mixtures based on Si3N4, the lower the shrinkage end temperature. The relative density achieved is 96 %. The ceramics based on Si3N4 powder with the dispersion of <1 µm are difficult to machine, characterized by the hardness of 19.0 ± 0.7 GPa and the crack resistance of 5.1 ± 0.4 MPa·m1/2. The flexural strength of the ceramics evaluated by the B3B method depends on the dispersion of Si3N4 powder and is more than 2 times higher for the ceramics based on the commercial Si3N4 powder with the dispersion of <1 μm.