Study On Thermal Spray Coating With Resistance To High Temparature Sulfide Corrosion
Yang Guoqing
CNKI
Abstract
Hot corrosion is the main reason to cause the machines or parts’ degrade at elevated temperatures. The oxidized film and corroded film formed on the surface of the metal will play an important role in the corrosion progress. Aluminum and Chromium are the best candidates since alumina film and chromium film are dense, stable, and continuous. Materials, such as steel and nickel, alloyed with aluminum and chromium can show active performance in hot corroding progress. It is as known that the corrosion happens from the surface of the metal.Through the way of arc spraying, we can get the arc-sprayed aluminum-based coatings and chromium-based coatings which could protect steelparts used at elevated temperatures from hot corrosion.
The results of the experiments revealed that the arc sprayed NiCr, 45CT, FeCrAl and FeCrAl/Al composite coatings could well protect the steel substrate from high-temperature corrosion. During the spraying process, Al and Cr element would form a continuous film of Al2O3 and Cr2O3 by elective oxidizing. There are a few protection zones of oxidized film in the coatings which could play an important role in resisting hot corrosion. The protection zones would play a roll in slowing the element diffusion. First, they could delay the diffusion of metal elements in the coating, and also they could play a roll in obstructing the corrosive elements’incursion. During the corrosion process, there would form a protective oxidizing film on the surface ofthe coating, which couldobstruct the corrosive elements’ incursion.
The tests in the scene of producing CS2 gave a strong proof that FeCrAl/Al composite coatings could significantly increase the ability of resisting the gray iron substrate from high temperature corrosion. Under the conditions of high sulfur and low oxygen atmosphere at elevated temperature, the inter diffusion of the elements in the composite coatings resulted in the formation of an intermetallic compound, AlCrFe. The same time, the oxidized filmof Al2O3 and Cr2O3 would formon the surface ofthe coating, which could protect the abstract.
Key Words：hot corrosion，arc spraying，diffusion，protective film
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