R.K. Fotedar

Effect of WSi2 addition on densification and properties of ZrB2

Abstract Effect of WSi2 addition on densification and properties of ZrB2 has been investigated. Samples of the following composition with controlled addition of WSi2 were prepared by hot pressing (1) ZrB2, (2) ZrB2+2·5%WSi2, (3) ZrB2+5%WSi2 and (4) ZrB2+10%WSi2. Hot pressing of monolithic ZrB2 at 1750°C resulted in achieving a density of only 80·1% ρth. Addition of WSi2 enhanced the densification and resulted in near theoretical density. Microstructural investigations revealed the presence of reaction product containing Si and Zr. An increase in WSi2 content led to an increase in hardness of the product. A slight increase in fracture toughness was observed with WSi2 addition. Crack deflection was observed in the microstructure. Oxidation study of the composite samples revealed that the oxidised layer is not adherent and resulted in spallation at the end of the test.

Synthesis, Densification and Characterization of Boron Carbide

This paper presents the experimental results on synthesis of boron carbide from its elements. Boron to carbon ratio of 4:1 and a synthesis temperature of 1850°C was found optimum to obtain stoichiometric B4C. Higher boron in charge resulted in the formation of boron rich phase B8C along with B4C but was not effective in eliminating free carbon in the product. Effect of hot pressing parameters on densification of boron carbide was investigated and the optimum operating parameters to obtain B4C pellets with a density of ≥95% TD were identified. Mechanical and thermal properties were characterized and compared with literature values.