Sintering of BN/cemented carbide composites under an electric field for improved mechanical performances

In the present study, attempts were made to fabricate cemented carbide (WC/Co) composites toughed with cubic boron nitride (cBN) for structural applications using a field assisted sintering technique. The effects of the content of cBN and the soaking time during the sintering process on the consolidation and mechanical performance of the materials were studied. It was found that with the increase of the cBN content from 0 to 30vol%, the densification of the composites was hindered and relative density decreased from 99.5% to 92.18%. Phase transformation of the cBN to the hexagonal structure was related to the content of cBN due to the joule heat generated in the interface and tended to occur when a cBN content higher than 5vol% was incorporated and sintered for more than 8 min. Both the hardness and toughness showed considerable improvements with an introduction of 5 vol% cBN and continuous decrease with its further addition. A maximum enhancement of around 12% and 20% were achieved for the hardness and toughness respectively. A long period sintering degraded the mechanical performances of the cBN-WC/Co composites by forming the pores or holes and promoting the phase transformation of the cBN. The results obtained are expected to lay a foundation for the fast fabrication of high performance structural materials.