The Preparation And Properties Of SiC/B₄C Composite Ceramics By Reactive Sintering

Silicon carbide (SiC) and carbonization boron (B4C) are typical superhard materials, with high melting point, high hardness, good thermal conductivity and conductivity, can be widely applied in the tool material and high temperature structural materials. But, because of its covalent bond is very strong, it is extremely difficult to sintering dense ceramic materials. Reaction sintering is a kind of method which could at relatively low temperatures by permeability silicon reaction got sintered body get density. This study through the B4C and SiC content changes, is the preparation of B4C/SiC ceramics material by vacuum of reaction sintering procedure.This study uses B4C,SiC, C as main raw materials, getting preparation green body by in situ solidification-prilling- pressure molding. Infiltration Si at the vacuum sintering process of reaction sintering, and controlling the reacting temperature at 1550℃and 2 hours heating time. SiC/ B4C ceramic materials is preparation out, respectively by SiC primarily phase or B4C primarily phase.This study through the formula design, controlling the fSi volume content in reaction sintering SiC/B4C ceramic materials for 12～16vol%. Based on density and B4C content, SiC/C proportioning calculation method is derived.A series of different B4C content of SiC/B4C ceramics material is designed。The ceramic mechanical's microstructure and mechanical property of different B4C content were discussed.The results show that the SiC/B4C composites are compact structure and mainly composed of B4C,α-SiC, (3-SiC and Si. The chemical compatibility of SiC, B4C and Si is good, obtained by the compact structure of sintered body without hole.The main fracture of ceramic materials is intergranular fracture.With the increase of B4C content, the hardness of the composite increases gradually. the hardness of the composite with 85wt% B4C is 33.2 GPa. Bending strength of the composite with 40wt%B4C is 475.4 MPa. Fracture toughness of the composite with 40wt%B4C is 5.84MPa.m1/2.By mierostructures observation and mechanical properties discussion,reinforce- ment of toughness is interpreted as residual stress and micro-crack via mismatch of thermal expansion between SiC, Si and B4C.This research shows that taking low temperature reaction sintering in phase preparation of SiC/B4C ceramic materials is a low cost obtain effective method of dense ceramic materials.