Synthesis of SiC<sub>W</sub>/(Mo,W)Si<sub>2</sub> Composite by the "Chemical Oven" Self-Propagating Combustion Method

Abstract

SiC whisker reinforced (Mo,W)Si2 composite powder has been successfully synthesized by a novel process, named as chemical oven self-propagating high temperature synthesis (COSHS). The mixtures of Si and Ti powders were ignited as chemical oven. XRD result shows that the combustion product is mainly composed of (Mo,W)Si2 solid solution and SiC phases. SEM photo and EDS result show that SiC whisker is formed during this process. The as-prepared SiCW/(Mo,W)Si2 composite powder has been pressureless sintered. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite are 91.2% and 92.2%, respectively. The composite containing SiC whisker and (Mo,W)Si2 solid solution has higher Vickers hardness than monolithic MoSi2. Especially the room-temperature flexural strength of the composite is higher than that of monolithic MoSi2, from 135.5MPa for MoSi2 to 235.6MPa for composites with 10 vol.% WSi2 and 15 vol.% SiC, increased by 73.9%. The morphology of fractured surface of composite reveals the mechanism to improve flexural strength of MoSi2. The results of this work show that in situ SiCW/(Mo,W)Si2 composite powder prepared by COSHS technique could be successfully sintered via pressureless sintering process and significant improvement of room temperature flexural strength could be achieved. It could be a cost-effective process for industry in future applications.