ZrB2–SiC based composites for thermal protection by reaction sintering of ZrO2+B4C+Si

Abstract

Synthesis and sintering of ZrB2–SiC based composites have been carried out in a single-step pressureless reaction sintering (PLRS) of ZrO2, B4C, and Si. Y2O3 and Al2O3 were used as sintering additives. The effect of ratios of ZrO2/B4C, ZrO2/Si, and sintering additives (Y2O3 and Al2O3), was studied by sintering at different temperatures between 1500 and 1680 °C in argon atmosphere. ZrB2, SiC, and YAG phases were identified in the sintered compacts. Density as high as 4.2 g/cm3, micro hardness of 12.7 GPa, and flexural strength of 117.6 MPa were obtained for PLRS composites. Filler material was also prepared by PLRS for tungsten inert gas (TIG) welding of the ZrB2–SiC based composites. The shear strength of the weld was 63.5 MPa. The PLRS ZrB2–SiC composites exhibited: (i) resistance to oxidation and thermal shock upon exposure to plasma flame at 2700 °C for 600 s, (ii) thermal protection for Cf–SiC composites upon exposure to oxy-propane flame at 2300 °C for 600 s.