1996 Volume 14 Issue 2 Pages 333-337
SiC was brazed to SiC with Cu-Ti alloys containing Ti content up to 50 at% at 1373 K for 1.8 ks in vacuum, where pressureless sintered SiC were used. The strength of SiC/SiC joints were measured by 4-point bending test at room temperature and elevated temperature. The microstructures and elemental distribution and reaction phases in the joining layers were investigated by means of electron probe micro-analyser and X-ray diffract-meter. The main results obtained are summarized as follows.
(1) The strength of SiC/SiC joint increases with increasing Ti content in Cu-Ti alloys for Ti content up to 34 at%, and shows the maximum of 208 MPa at Ti content of 34 at%.
(2) Ti in the alloys with Ti content up to 15 at% reacts with SiC and forms TiC, Ti5Si3 and TiSi. Ti in the alloys with Ti content from 20 at% to 25 at% reacts with SiC and forms TiC, Ti3SiC2, Ti5Si3 and TiSi. Ti in the alloys with Ti content of 34 at% or more reacts with SiC and forms TiC, Ti3SiC2, TiSi and TiSi2.
(3) The formation of TiC and Ti5Si3 at the interface between SiC and Cu-Ti alloy prevents the direct reaction of copper with SiC, and reduces the thickness of the brittle copper penetrating layer. The formation of thick carbide layer of Ti3SiC2 is attributable to the maximum strength of SiC/SiC joint.
(4) The SiC/SiC joint brazed with Cu-34 at% Ti alloy represents the strength of 208 MPa up to testing temperature of 723 K, and the degration of strength with further increasing the temperature.