Metal Coatings Used in the Aerospace Industry

As the heart of an airplane, the working environment of an aero engine can be said to be extremely bad. It feels like putting people in the desert without food or drink, and you have to work. The reason why the engine can withstand high temperature, high pressure, high speed, ablation, and other bad environment has a lot to do with the coating on various parts. The coating is like a girl’s powder, which can be used to protect a girl’s makeup, while the coating can protect aircraft engine parts. This is the aero engine coating removal technology we are going to talk about today.

Metal materials (such as aluminum, titanium, magnesium and other non-ferrous metals and their alloys) have become the most widely used materials in the field of aviation and aerospace due to a series of excellent properties, such as non-moisture absorption, good dimensional stability, excellent thermal and electrical conductivity, etc. They are often seen in various types of spacecraft shell, skin, fine structure parts and spacecraft platform, skeleton structure, tooling. Here are some common metal coatings used in the aerospace manufacturing industry.

surface treatment

Aluminide coating

The surface of the coating will be passivated by the use of the oxidizing acid solution, while the groove solution with the high concentration of pitting reagent is the most effective. Organic solvents are fatty compounds with high volatile temperature, and there is no degradation of organic solvents at the removal of coating temperature. Pitting acid in aqueous solution is more likely to cause pitting corrosion of high-temperature alloy than that in the organic solvent solution, and the organic solvent solution of pitting acid can even remove the coating and dissolve the coating quickly. The oxide film on the surface of the coating hinders the removal of the coating. Therefore, the sand should be blown out before removing the aluminum poor coating.

Nitride ceramic coating

Titanium nitride (TiN) series ceramic coating films have high hardness and oxidation resistance and are characterized by wear resistance, erosion resistance, and corrosion resistance, etc., which have been used to protect the blades of the rotor blades of the engine compressor.

Nickel coating

Nickel (Ni) coating has excellent wear resistance, corrosion resistance, and other properties, and has been widely used in aircraft engine parts. Generally, the nickel coating is removed by the chemical method, and the nickel is oxidized to Ni by the active oxidant. In the process of coating removal, if the part substrate is exposed in a certain area, the corrosion inhibitor in the solution will be adsorbed on the surface of the substrate in some way, so as to generate the corrosion resistance protective film to protect the part substrate.


Thermal barrier coating

The thermal barrier coating is one of the key components of aero-engine turbine blades. Yttrium oxide and partially stable zirconia are the most mature and reliable thermal barrier coating materials.

In conclusion, although many studies have been carried out on the removal technology of zirconia thermal barrier coatings, no effective removal method has been found, and the sand blowing method is still adopted. As the engine, hot end component with the most severe service condition, thermal barrier coating repair of the turbine blade and guide blade occupy the main production share of the engine overhaul. Therefore, it is especially necessary to carry out the research and engineering application of thermal barrier coating removal technology for the thermal end parts of aero-engine.

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