Preparation and properties of α′ and α′ + β′-sialon ceramics

The densification of a'- and a'+ß'-Sialon ceramics was studied by in situ dilatometry. The densification is greatly affected by the reaction sequences and the grain growth. The formation and densification of Sialon start simultaneously as the dissoln. of nitrides into the oxide eutectic liq. phase occurs. The formation of Sialon is complete at 1800 Deg, while full densification can only be obtained by using gas pressure sintering. The typical microstructure of both a'- and mixed a'+ß'-Sialon ceramics consists of a cryst. phase of Sialon and a small fraction of amorphous phase at grain boundaries. Vickers hardness (HV0.5) was measured by using the indentation technique, and the biaxial bending strength (sbi) was detd. with the ball-on-ring test. Fracture toughness was detd. by using both the indentation and SENB (single-edged notched beam) techniques. Increasing the amt. of oxide additive(s) leads to deterioration in the mech. properties of the final products of a'+ß'-Sialon, due to a change of compn. and microstructure. [on SciFinder (R)]