High-temperature properties of ZrB2–HfB2 and ZrB2–HfB2–SiC solid solutions

Solid (ZrxHf1–х)B2 and (ZrxHf1–х)B2–15 vol.% SiC composites were obtained by hot pressing. It was shown that the formation of homogeneous solid solution occurs at an equimolar ratio. The coreshell structure was formed in composite with 25 and 75 at.% HfB2. In the first case, the core was pure zirconium diboride, and in the second – pure hafnium diboride. The shell composition corresponded to the chemical formula (Zr0.75Hf0.25)B2 or (Zr0.25Hf0.75)B2, respectively. The formation of an equimolar solid solution results in a 28% increase in high temperature bending strength in comparison to ZrB2–15 vol.% SiC or HfB2–15 vol.% SiC. At the same time, high oxidation resistance is observed in a solid solution close to hafnium diboride due to the formation of the (Hf0.75Zr0.25)SiO4 and HfSiO4 phases on the scale surface, which reduce the diffusion of oxygen into the material