NDLI: Sulphidation Behavior of a Non Harmful Water-Based Al and Al

Content Provider	Springer Nature Link
Author	Montero, X. Galetz, M. C. Schütze, M.
Copyright Year	2013
Abstract	Slurry aluminide coatings are widely applied to protect metallic surfaces from oxidation and corrosion. They are frequently used in gas turbine engine nozzles because of economical advantages and a straight-forward manufacturing route. A variety of commercial slurries are available to aluminize the surfaces of nickel-based superalloys, however, they have two main disadvantages. First, the phosphates and chromates or halides used as binders and to activate the diffusion species are environmentally harmful; second, the conventional systems have to be heat-treated in an inert atmosphere. As an outcome of the PARTICOAT project the variety of slurry derived coatings has been extended by tailoring the particle size of the metallic source. By doing that, environmentally friendly water-based slurries were developed to produce in a one-step process und atmospheric conditions, a thermal barrier system based on an aluminum diffusion layer and an alumina foam layer which serves as bond coat as well as top coat (TC). CM 247 nickel base superalloy was coated and heat-treated in air using newly developed Al and Al–Si slurries. The oxidation behavior was investigated at 1,000 °C and then compared to pack-cemented aluminide coatings. The sulphidation behavior was investigated at 1,000 °C in an atmosphere of 1.5 vol% SO$_{2}$ in synthetic air for Al and Al–Si slurry coated samples with and without the alumina foam TC layer. PARTICOAT Al-based slurries,, after the initial stabilization of the TC, showed similar oxidation kinetics as pack cemented aluminides when exposed to air. When the coatings were exposed to sulphide-containing atmospheres, their oxidation rates increased, producing typical type I corrosion damage. Coatings without TC produced more protective oxide scales. The weight gain and coating area affected by corrosion were slightly lower for the Al-based slurries after 1,000 h of exposure than for the Al–Si based ones. The new coating presented here offers unique advantages in comparison to state-of-the-art slurry and pack cemented coatings by opening a potential way to manufacture a complete thermal barrier coating system by a simple, inexpensive and environmentally safe deposition and heat-treatment in air.
Starting Page	635
Ending Page	649
Page Count	15
File Format	PDF
ISSN	0030770X
Journal	Oxidation of Metals
Volume Number	80
Issue Number	5-6
e-ISSN	15734889
Language	English
Publisher	Springer US
Publisher Date	2013-08-09
Publisher Place	Boston
Access Restriction	Subscribed
Subject Keyword	Aluminum Slurry Co-deposition Thermal barrier Diffusion coating Hot corrosion Sulphidation Oxidation Metallic Materials Inorganic Chemistry Tribology, Corrosion and Coatings
Content Type	Text
Resource Type	Article
Subject	Materials Chemistry Metals and Alloys Inorganic Chemistry

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