Study On Joining Technology Of Ti?C,N?-Al₂O₃ Ceramic Matrix Composite

Ti?C,N?-Al₂O₃ ceramic matrix composite?CMC? is a kind of super hard materials which has a wide using prospect. Steiner is the forming way of the CMC that usually employed in industry. The complex part of CMC is always fabricated by welding. However, the welding methods could be employed in CMC joint are usually few due to the character of high brittle. Based on these discussion, the vacuum brazing and vacuum transit liquid diffusion bonding processes were studied in this investigation.The CMC was brazing joined with the help of CuTi and CuZr at 950 ? in vacuum furnace. The structure and joining mechanism of joints were investigated by optical microscope?OM?, scanning electron microscope?SEM?, and X-ray diffracts?XRD? analysis. The mechanical property of CMC joints was measured by four-point bending test. The fracture mechanism of brazing joints was studied based on the fracture surface observation and finite element analysis?FEA?. The results showed that the reaction mainly occurred between Al₂O₃ reinforcement in CMC and Ti from CuTi filler metal generating Ti3 Al intermetallic compound?IMC? and Cu3Ti3 O compound when brazed by CuTi filler metal. The reaction mainly occurred between Al₂O₃ reinforcement in CMC and Zr from CuZr filler metal generating ZrO2 and Al when brazed by CuZr. The Al diffused toward brazing seam reacted with Zr generating Al9.83Zr0.17. The residual Al diffused deeply and reacted with Cu forming Al4Cu9 IMC. The bending strength of CuTi joint increased first and declined then as a function of brazing time. The bending strength of joint brazed for 30 min was the maximum. The fracture occurred in CMC matrix. When the brazing time was 5 min, 15 min, and 60 min, the crack was started in brazing seam then propagated into CMC matrix. The bending strength of CuZr joint was all below 200 MPa. The fracture mode was the mixed fracture of filler metal and Ti?C,N?-Al₂O₃ CMC mate.The Ti/Cu/Ti and Zr/Cu/Zr middle layer was employed to realize the transit liquid diffusion joining of CMC at 980 ? in vacuum furnace. The SEM was employed to investigate the forming mechanism of joint. The four-points bending test was employed to study the mechanical property of the CMC joint. The fracture mechanism was investigated by the fracture surface observation. For Ti/Cu/Ti joint, CuTi IMC formed as the diffusion of Ti into Cu. The?Cu, Al?Ti IMC generated due to the Al atom dissolution effect in CuTi IMC. For Zr/Cu/Zr joint, the Cu8Zr3 IMC generated between Zr and Cu layers due to the interdiffusion. Then the IMC reacted with Al₂O₃ forming dilution zone of Zr/Cu/Zr joint. The bending strength of transit liquid diffusion joint increased as the diffusion time increased. The crack initiated in diffusion seam first and propagated into CMC when the diffusion time was 5 min, 15 min, and 30 min for Ti/Cu/Ti joint. The joint fracture was in CMC matrix when the diffusion time was 60 min. The fracture of Zr/Cu/Zr was the mixed fracture of middle layer and CMC matrix. The fracture of middle layer was located in the dilution region of CMC matrix.