Statistical evaluation of mechanical characteristics of hot-pressed ceramics in ZrB$_2$–SiC system

The effect of the addition of $5$ mol.% LaB$_6$ on the Weibull modulus of hot-pressed ceramics in ZrB$_2$-SiC is studied in this paper. The samples with a relative density of $91$–$92\%$, a flexural strength of $300$–$315$ MPa, and a Vickers hardness of $14$–$15$ GPa are obtained by hot pressing at an isothermal holding temperature of $1900^\circ$C and a pressure of $30$ MPa within $15$ minutes in an argon atmosphere. The addition of LaB$_6$ induces an increase in the Weibull modulus of ceramics from $9.5$ up to $15.5$ when calculating using the bending strength, and from $22.0$ up to $31.4$ when calculating using the hardness. The values calculated using the hardness are somewhat overestimated due to the local impact of the Vickers pyramid. An increase in the Weibull modulus with the addition of LaB$_6$ is associated with increasing homogeneity of the ceramic structure due to the formation of a more developed system of interphase boundaries in three-component samples.