The Joinning And Technology Research Of SiC Ceramic And Metal

SiC ceramic has superior mechanical and thermal physical properties such as chemical property stability, high mechanical properties, good anti-radiation ability. It's a promising structural ceramics as a key material to manufacture automobiles, spacecraft and other high-temperature structural engine components. But it is difficult to meet the need under special and harsh condition because of its intrinsic brittleness. Only through the connection technology to make complex shape of parts with other materials as a composition structure could bring into full play the respective advantages. And as the current industrial development to see, The connection of SiC ceramic and metal has a bright prospects. It has a vital significance in the future development of the new type high temperature resistant, fight oxidation structure to achieve the reliable connection between SiC ceramic and metal.SPS technology has published several decades. It is widely used in the field of the preparation of nano materials, functional gradient materials, metal materials, composite materials, ceramic materials,etc and the connection of ceramic powder and metal powder, solid-powder-solid material, etc. The diffusion bonding as a frequently connection technology, widely used in a variety of material system:metal/metal, metal/ceramic, ceramic/ceramic, etc. For the present, the diffusion bonding is more for used in radiation heating. It limited the using temperature range because of the uniform temperature distribution of the sample in connection process.In this thesis, SPS technology as a heating source of the diffusion bonding to connect SiC/W. We take direct connection and add layer material connection to explore the impact of the intermedium, analysis the microstructure and performance. In the research of the direct connection, we discuss the interface situation of the different temperature and make the spectrum analysis to it. Then we have the conclusion: It occurs mutual diffusion on both sides of the interface. The reaction products were analyzed by XRD. The results showed that the main products are WCx,W5Si3,SiC. It is full of toughness nest in the W substrate of the disconnect part and the particles combined closely. The transcrystalline fracture of the W substrate demonstrate that it exists huge residual heat stress within the joint. ANSYS was used to simulate the temperature-stress distribution field for the connection process. The stress is intensively distributed in the tiny region near the outer surface and the parts of the joint. W layer bears radial stress, SiC layer bears radial stress, and the high stress area occurs near the interface, stress in W layer is obviously greater than the stress in SiC layer. The stress in the W layer is increasingly add from the center of the W along the longitudinal axis to outside surface extensions, on the contrary, the stress in the SiC layer is increasingly reduce from the center of the W along the longitudinal axis to outside surface extensions.In the add layer material connection, the intermediums are Si+C+10wt%W, Si+C+30wt%W,Si+C+50wt%W,Si+C+70wt%W. For Si+C+50wt%W layer, the reaction is incomplete when the temperature is below1400℃,it also exists Si,C powder when the W content is lower than50wt%, the main products are SiC,WSi2When the W content is above50wt%. energy spectrum analysis shows that different degrees of element mutual diffusion occurred in the interface. It shows different microstructure under the different technological parameter. We find holes in W substrate in the vicinity of the interface. And the width of the hole is increased with the content of W. It against the interface reaction and element diffusion if the heat preservation time is too short, at the same time,easy to produce unstable transition phase W5Si3; heat rate is also a vita factor to the formation of the joint. The middle hardness is lower than the matrix materials, connection temperature has a significant impact to the bending strength, and in1400℃achieve the highest connection strength.