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What are transonic airfoils, and what is the active clearance control? Check out our technical dictionary and find out more about engine technology terms – from active clearance control to velocity triangle. Active clearance control (ACC) Adaptive HSC milling Afterburner Airfoil bitangent line Airfoil chord Aluminizing and chromizing Aluminum oxide dry blasting Aluminum oxide wet blasting Annular combustion chamber Anodizing Atmospheric plasma spraying (APS) ATFI Axial-flow compressorAtmospheric plasma spraying (APS)
In the process, a constricted arc with high energy density burns between a centrally arranged bar-shaped tungsten cathode and an annular water-cooled copper anode. The major part of the heat energy of this arc is transmitted to the gas (argon, helium, nitrogen, hydrogen) flowing between cathode and anode. The gas is thus ionized and transferred into the plasma state. Upon recombination the heat energy absorbed is released again while an electrically neutral plasma jet exits the nozzle of the plasma torch at a high velocity (Mach 2 max.) and a high temperature (approx. 20,000K max.). A carrier gas feeds the coating powder into the plasma flame (inside or outside the torch) where it is melted and sprayed onto the pre-treated component surface.Because of the very high temperatures all coating materials (metals, high-melting oxides, carbides, nitrides,silicides) can be melted and sprayed. Since the dwell time of the powder in the plasma is very short (some 10-6 s) and the spraying materials must be fully molten without vaporizing, it is important that the optimum particle size is strictly adhered to.
Plasma spraying is used to produce
- seal coatings
- dimensional correction coatings
- wear protection coatings
- thermal barrier coatings
- electrical insulation coatings
Plasma spray coatings are characterized by a relatively good adhesive strength (20 - 70 MPa) and a porosity that can be adjusted for the application in question between 1% to 20%.