At present, the preparation methods of SiC coating mainly include gel-sol method, embedding method, brush coating method, plasma spraying method, chemical gas reaction method (CVR) and chemical vapor deposition method (CVD).
Embedding method:
The method is a kind of high temperature solid phase sintering, which mainly uses the mixture of Si powder and C powder as the embedding powder, the graphite matrix is placed in the embedding powder, and the high temperature sintering is carried out in the inert gas, and finally the SiC coating is obtained on the surface of the graphite matrix. The process is simple and the combination between the coating and the substrate is good, but the uniformity of the coating along the thickness direction is poor, which is easy to produce more holes and lead to poor oxidation resistance.
Brush coating method:
The brush coating method is mainly to brush the liquid raw material on the surface of the graphite matrix, and then cure the raw material at a certain temperature to prepare the coating. The process is simple and the cost is low, but the coating prepared by brush coating method is weak in combination with the substrate, the coating uniformity is poor, the coating is thin and the oxidation resistance is low, and other methods are needed to assist it.
Plasma spraying method:
The plasma spraying method is mainly to spray melted or semi-melted raw materials on the surface of the graphite matrix with a plasma gun, and then solidify and bond to form a coating. The method is simple to operate and can prepare a relatively dense silicon carbide coating, but the silicon carbide coating prepared by the method is often too weak and leads to weak oxidation resistance, so it is generally used for the preparation of SiC composite coating to improve the quality of the coating.
Gel-sol method:
The gel-sol method is mainly to prepare a uniform and transparent sol solution covering the surface of the matrix, drying into a gel and then sintering to obtain a coating. This method is simple to operate and low in cost, but the coating produced has some shortcomings such as low thermal shock resistance and easy cracking, so it cannot be widely used.
Chemical Gas Reaction (CVR) :
CVR mainly generates SiC coating by using Si and SiO2 powder to generate SiO steam at high temperature, and a series of chemical reactions occur on the surface of C material substrate. The SiC coating prepared by this method is closely bonded to the substrate, but the reaction temperature is higher and the cost is higher.
Chemical Vapor Deposition (CVD) :
At present, CVD is the main technology for preparing SiC coating on the substrate surface. The main process is a series of physical and chemical reactions of gas phase reactant material on the substrate surface, and finally the SiC coating is prepared by deposition on the substrate surface. The SiC coating prepared by CVD technology is closely bonded to the surface of the substrate, which can effectively improve the oxidation resistance and ablative resistance of the substrate material, but the deposition time of this method is longer, and the reaction gas has a certain toxic gas.
Post time: Nov-06-2023