High-temperature oxidation of ZrB2–SiC and ZrB2–SiC–ZrSi2 ceramics up to 1700°C in air

The high-temperature oxidation of ZrB 2 –SiC and ZrB 2 –SiC–ZrSi 2 ceramics up to 1700°C in air has shown their high corrosion resistance. A five-stage nonisothermal oxidation mechanism is established for the samples when heated at a rate of 20°C/min: 1) oxygen adsorption–desorption; 2) formation of ZrO 2 and B 2 O 3 oxides; 3) formation of α-SiO 2 cristobalite and ZrSiO 4 zircon; 4) formation of amorphous SiO 2 ; and 5) formation of upper protective borosilicate film with ZrSiO 4 inclusions at less than 40 wt.% SiC. It is shown that small ZrSi 2 admixtures (