Microstructural evolution and contact-mechanical properties of SiC ceramics prepared colloidally with low additive content

The microstructural evolution and contact-mechanical properties of liquid-phase sintered (LPS) SiC ceramics processed colloidally with low loads of sintering additives was investigated as a function of the sintering duration, and was compared with the case of their counterparts processed conventionally. The two processing routes differ in the preparation of the powder batch, which in the colloidal method is done by covering the SiC particles with an oxide nano-film synthesized by the sol-gel method, whereas in the conventional method it is done by mixing mechanically the SiC powder with the oxide powders. It was found that the colloidal processing route offers clear benefits in terms of densification and contact-mechanical properties (stiffness, hardness, and damage and wear resistances) over the conventional processing route when the sintering times are short, but not when the sintering times are moderate or prolonged. Furthermore, no differences were found in the microstructural evolution with the sintering duration between the two types of ceramics. Based on the results, it is proposed that the more sophisticated colloidal processing route is certainly the appropriate choice for short sintering times, whereas in other cases its use would be justified if the goal is to incorporate into the microstructure new homogeneous multi-component oxide additives with tailored stoichiometry.