Comparative evaluation of TiC and/or WC addition on microstructure, mechanical properties, thermal residual stress and reciprocating wear behaviour of ZrB2-20SiC composites

Abstract

The present study aims to evaluate and compare the effect of 5 vol.% TiC or WC addition on densification, phase stability, microstructure, mechanical properties, thermal residual stress and reciprocating wear behaviour of spark plasma-sintered ZrB2-20 vol.% SiC composite. ZrB2-20SiC-5TiC (vol.%) composite attains 99.6% mean sintered density even at 1700 degrees C, while WC containing composites (ZrB2-20SiC-2.5TiC-2.5WC and ZrB2-20SiC-5WC, vol.%) necessitates a sintering temperature of 1800 degrees C for > 98% densification. Phase and microstructure analyses confirm that respective incorporation of TiC and WC leads to in situ formation of (Zr,Ti)B-2 and (Zr,W)B-2 solid solution in the sintered composite. Elastic modulus and thermal expansion coefficients of the composites have been estimated utilizing well-established analytical models. The thermal residual stress of the sintered composites is determined analytically utilizing Taya's model and Hsueh's model and compared with residual stress of SiC reinforcement determined by Raman spectroscopy. Nano-indentation analysis confirms that the minimum resistance to deformation and maximum plasticity index are observed in ZrB2-20SiC-2.5TiC-2.5WC composite due to its relatively low elastic modulus. The maximum Vickers hardness is observed in ZrB2-20SiC-2.5TiC-2.5WC composite, whereas an excellent combination of indentation toughness and indentation modulus is found in ZrB2-20SiC-5WC. Owing to relatively high fracture toughness exponent and low brittleness index, ZrB2-20SiC-5WC composite records the minimum wear volume and wear rate in linear reciprocating wear test. [GRAPHICS] .