Traditional ceramic materials have excellent properties such as high hardness, high-temperature resistance, and corrosion resistance. However, its application is limited due to its brittle quality, toughness, and strength.
With the development of nanometer science, it is found that nanometer powders show many special properties such as surface effect, small size effect, and quantum size effect, and nanoceramics coating is also a general term for a large class of inorganic non-metallic coatings that have emerged after organic resin coatings, metal and alloy coatings. Since the 1990s, nanoceramics coating in aerospace, electronics, military, and other cutting-edge areas have been developed continuously at high speed.
The application of nanoceramic coatings can be roughly divided into the following categories according to the different coating functions.
Nanostructured ZrO2 thermal barrier coating
The thermal barrier coating (TBC) is mainly used in the high-temperature atmosphere or thermo-corrosive static and dynamic atmosphere, which can significantly reduce turbine surface temperature, increase gas turbine power and improve thermal efficiency. It has been successfully applied to aero engines and will be extended to engines for diesel engines as well as for cars and motorcycles.
Nanostructured thermal barrier coatings have been widely studied and applied for their better properties. The nanostructured ZrO2 coating has low thermal conductivity, similar thermal expansion coefficient to metal and good stability at high temperature, which is the representative of thermal barrier coating at present.
Nanostructured WC/Co coating
Tungsten carbide/cobalt (WC/Co) metal-ceramic coating is an excellent anti-friction and wears material. The nanostructured WC/Co coating has high hardness, good bonding strength, and good toughness, and can be used in aerospace, automobile, metallurgy, electric power, and other fields to enhance the wear resistance of matrix metals and repair wear parts. For example, the working conditions of aircraft engine parts are very bad, and they are tested by adhesive wear, abrasive wear, corrosion wear and fatigue wear, so the performance and life of the engine are seriously affected.
Nanostructured self-lubricating coating
It is well known that friction and wear mainly occur on solid surfaces. Unlike the general friction parts, special lubricating materials and lubricating methods must be developed to ensure the normal operation of the moving joints which work in the vacuum or at low temperature or high temperature. This coating can be applied to a variety of mechanical parts, such as the piston, cylinder body, bearing, gear, heavy-duty rear shaft handle, CAM, especially roller, supporting shaft and other parts that are difficult to be lubricated.
Nanostructured Al2O3/TiO2 coating
The nano Al2O3/TiO2 coating overcomes the defect of low binding strength and toughness of conventional coating and has a long service life and reliability. As a result, it can replace conventional ceramic coatings in large quantities, and also be applied in places where it was previously difficult to apply the coating. The nano Al2O3/TiO2 coating has higher binding strength than the ordinary coating and can also deform with the covered matrix material. Ceramic coating technologies for such nanostructures can significantly increase the life of components used in ships, spacecraft and land vehicles, saving the military and civilian industries tens of billions of dollars a year in maintenance and replacement costs.
Nano TiO2 coating
Nano TiO2 coating is applied to steel corrosion protection, which is equivalent to cathodic protection as electroplating sacrificial metal. However, nano TiO2 coating does not undergo anodic dissolution, so it can be used as permanent anti-corrosion coating. Nano TiO2 coating applied to stainless steel antisepsis can achieve a good effect, and it has more scientific significance and economic value if nano TiO2 coating can achieve the specified antisepsis effect on the largest amount of low carbon steel.
Due to the refinement of nanoceramics coating grains, the grains are dispersed uniformly, while the number of grain boundaries increases greatly, and the planar coagulability of the particles is obviously better than that of micron particles, so the coating structure is more compact. Nanoceramics coating has been widely used in aerospace, machinery, ship and chemical industries due to its advantages in the high-temperature thermal barrier, wear resistance, self-lubrication and corrosion resistance.
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