Journal
SURFACE & COATINGS TECHNOLOGY
Volume 441, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.surfcoat.2022.128579
Keywords
Composite coating; NiAl-Al2O3; Electrodeposition; Self-healing coating; Oxidation
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This study explores a new type of self-healing coating for high temperature oxidation applications. Micro-reservoirs consisting of an aluminium-rich intermetallic core and an aluminium oxide shell are embedded in a nickel aluminide matrix. The micro-reservoirs form a diffusion barrier and release aluminium into the coating matrix, maintaining a sufficient amount of aluminium and increasing the lifespan of the coating.
Nickel aluminide diffusion coatings act like an aluminium reservoir to form protective alumina scales at high temperatures. However, interdiffusion phenomena play a critical role in the metallurgical integrity of these coatings. This work explores a new type of self-healing coating for high temperature oxidation applications. Micro-reservoirs consisting of an aluminium-rich intermetallic core (Al3Ni2) and an aluminium oxide shell are embedded in a nickel aluminide matrix (NiAl). This new type of coating has been synthesized by an electrochemical chemical route to trap the micro-reservoirs in an electrodeposited nickel matrix followed by aluminization via a slurry route. Under high temperature oxidation conditions, the micro-reservoirs allow to form a diffusion barrier and to release Al into the coating matrix. These two simultaneous phenomena make it possible to maintain a sufficient amount of aluminium and ensure the unique formation of alpha-alumina at the surface of the coatings, hence to possibly increase the lifespan of the aluminium diffusion coatings.
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