Silicon carbide (SiC) has good thermal shock resistance and chemical stability, so it has a good application prospect under high temperature and extreme conditions, and has a wide range of applications in the field of engineering ceramics, such as bearings, gas turbines and heat exchangers. However, SiC ceramics are difficult to process, especially to form complex shapes, and traditional processes such as powder sintering and thin film deposition and consolidation have many limitations, which affect their high temperature performance, environmental resistance and high strength.
The University of Nuremberg, Germany has carried out a new process study on the preparation of reaction-bonded silicon carbide structures. The researchers dispersed SiC powder and carbon powder in the binder as materials, extruded and formed them with a nozzle mounted on a six-axis mechanical arm, and then used liquid silicon infiltration technology after pyrolysis at 700 ℃ and heat treatment at 1850 ℃. Infiltrate the sample to obtain a dense, near-net shape RBSC structure. Using the nozzles with diameters of 1.5mm and 0.5mm to print the grid microstructure as shown in Figure 1, it has good accuracy.
From the CAD model to printing a streamline structure, and then pyrolysis and reaction sintering, this process proves that the process can form complex shapes, and has good structural stability and near net forming ability.
After removing organic matter by pyrolysis, SiC and C particles are clearly visible, then after siliconizing treatment, Si and C react to form new SiC to make the microstructure dense, and finally remove the residual Si by acid etching. Throughout the process, the microstructure The uniformity is better.
The Young's modulus of the sample is 356.3 ± 7.9 GPa, which is equivalent to the reaction sintered silicon carbide of 20vol% residual silicon reported in other literatures. It also has a Vickers hardness of 19.8 GPa, which is comparable to the reaction combined silicon carbide produced by traditional processes. However, the bending strength obtained by the four-point bending test is 224.4 ± 86.0 MPa, which is slightly lower than 190-350 MPa reported in other literatures.