Comparative degradation of nickel aluminized by slurry and by pack cementation under isothermal conditions

• Published in: Corrosion science Vol. 66; pp. 118 - 124
• Main Authors: Mollard, M., Rannou, B., Bouchaud, B., Balmain, J., Bonnet, G., Pedraza, F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2013; Elsevier
• Subjects: Aluminium; Applied sciences; Corrosion; Corrosion environments; Exact sciences and technology; Kinetic parameters; Metal coatings; Metallic coatings; Metals. Metallurgy; Nickel; Oxidation; Oxide coatings; Production techniques; Surface treatment; Metal coatings; Aluminium; Nickel; Oxidation; Kinetic parameters; Oxide coatings; Isothermal condition; Metal coating; Corrosion; Pack carburizing; Kinetics; Surface treatment
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2012.09.009

[Display omitted] ► Degradation mechanisms of a new TBC slurry system containing Al microspheres elucidated on pure nickel substrate. ► Greater oxidation kinetics of slurry compared to conventional pack coatings. ► Major role of the top coat of alumina hollow spheres to mass gains. ► Greater changes in composition and microstructure in slurry coatings than in pack. ► Delayed transformation of theta-alumina in pack compared to slurry coatings. The degradation mechanisms of pure nickel aluminized by a new slurry containing Al microparticles and by pack cementation were studied isothermally between 900 and 1100°C in air for 100h. The parabolic rate constants indicated faster oxidation kinetics in the slurry coated samples with respect the pack cemented ones. The change in microstructures and compositions of the coatings and of the thermal oxides were more marked in the slurry coatings. This was related to both Ni and Al interdiffusion. It is concluded that the remains of Al in the spheres contributed to an increased oxidation compared to the pack cemented coatings.