With the development of special refractory materials in high-temperature coating technology and production methods, with the development of science and technology and coating technology, surface coating technology has been applied to refractory materials. The function of the coating is constantly expanding. In addition to high-temperature anti-oxidation and corrosion-resistant coatings, high-temperature electrical insulation coatings, wear-resistant coatings, anti-atomic radiation coatings, high-temperature lubricating coatings, heat treatment protective coatings, and temperature-indicating coatings have also been developed. Layer, infrared radiation coating, spectral selective absorption coating, etc. The materials used for high-temperature coatings include glass beads, oxides, refractory compounds, cermets, minerals, etc.
High-temperature inorganic coatings are also called high-temperature ceramic coatings. It is a general term for a heat-resistant inorganic protective layer or surface film coated on the surface of metal or other structural materials. It can improve the heat resistance, wear resistance, oxidation resistance and corrosion resistance of the metal substrate, thereby prolonging the service life of the metal and saving precious metal materials.
High-temperature ceramic coatings are generally coated on metal structural substrates, and surface coatings for structural materials other than metals such as ceramics, refractory materials, graphite, etc. have also been developed.
In addition to high temperature resistance, high-temperature ceramic coatings and substrates are required to have high bonding strength, close to zero porosity, good corrosion resistance, high thermal and mechanical shock resistance, high diffusion activity of coating component atoms, and high The thickness is not large. So far, there is no coating that can be used under any working conditions, but only a few of the above-mentioned properties can be manufactured, such as high-temperature oxidation-resistant and corrosion-resistant coatings, high-temperature thermal insulation coatings, and wear-resistant coatings. , Anti-atom radiation coating and heat treatment protective coating, etc. There are many types of high-temperature ceramic coatings, according to their different materials: ceramic coatings, refractory oxide coatings, refractory compound coatings and cermet coatings.
There are many production methods for high-temperature ceramic coatings, mainly including sintering method, flame spraying method, plasma spraying method and vapor deposition method.
The sintering method is to sinter the glass frit that is composed of refractory oxide and meltable together with the substrate. The production method of ceramic coating belongs to this method.
The flame spraying method is to make refractory oxide into a rod with a diameter of 2~3cm, or into a fine powder, which is melted and sprayed on the treated substrate by a flame spray gun with an oxygen fast flame to produce a uniform The coating plasma spraying method uses the high temperature of 8000~15000C generated by the arc plasma spray gun to spray any substance that does not decompose or sublimate during melting, through the input device, and spray on the surface of the solid substrate after the high temperature melting. The vapor deposition method uses metal vapor, metal halide or other compound vapor, at a high temperature of about 1000~2500C, in contact with the surface of the workpiece in a vacuum, hydrogen, argon or other protective atmosphere, and undergoes decomposition, cracking, reduction, and replacement. In the process of reaction and diffusion, the reactants are deposited on the surface of the structural substrate to form a dense and high-melting heat-resistant coating with good adhesion to the substrate.
In recent years, composite high-temperature ceramic coatings are being developed. Crush various refractory oxides, carbides, nitrides and other composite materials to the specified fineness, and mix with inorganic binders to form a slurry, which can be directly coated on the furnace lining or structural substrate oxide materials at room temperature, refractory Although compound materials and cermet materials have the advantages of high melting point, large elastic modulus, and high temperature strength, they cannot be used as light structural materials due to their low tensile strength and impact resistance. The emergence of high-temperature ceramic fibers and fiber-reinforced materials has further improved the use value of special refractory materials. Since 1960, various high-temperature fibers, such as boron fiber, carbon fiber, oxide fiber, carbide, and argon fiber, have come out one after another. Various fibers have high toughness. At present, the manufacturing process and performance of high-temperature fiber, the composite molding process of reinforcing materials, and the application test of fiber composite materials are developing very rapidly.
