The reliability of particulate composites in the TZP/WC system

The paper presents results of investigations of mechanical properties of two particulate composites in TZP/WC system. The materials have the same volume fractions of constituent phases. They differ in the carbide phase dispersion. Samples with WC inclusions of about a few micrometers or below one micrometer were prepared. Selected mechanical properties (strength, fracture toughness, hardness) were investigated. The results of the Weibull modulus values were calculated on the basis of bending strength. The double-torsion tests allowed the critical values of stress intensity factor to be estimated, below which no slow crack propagation occurred. The results showed that the type of microstructure strongly influenced properties of the composite. Depending on inclusions dispersion the composite system reliability was changed. The results indicated that incorporation of the second phase into zirconia matrix could improve the average value of basic mechanical properties (hardness, fracture toughness or strength), but simultaneously, the reliability (Weibull parameter) of this material was distinctly decreased. It was established that the threshold value of slow crack propagation is increased in the composite material.