EDP Sciences Journals List
Issue J. Phys. IV France
Volume 03, Number C9, Décembre 1993
Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
Page(s) C9-499 - C9-509
DOI http://dx.doi.org/10.1051/jp4:1993953

Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température

J. Phys. IV France 03 (1993) C9-499-C9-509

DOI: 10.1051/jp4:1993953

Effect of palladium-based undercoat on the formation, structure and properties of diffusion aluminide coatings

P. Steinmetz1, S. Alpérine2, P. Josso2 and J.M. Claude1

1  Laboratoire de Chimie du Solide Minéral, Faculté des Sciences de 1'Université de Nancy I, BP. 239, 54506 Vandoeuvre cedex, France
2  ONERA, Direction Scientifique des Matériaux, BP. 72, 92322 Chatillon cedex, France


Abstract
Coatings with Pd-Ni predeposit alloys have been processed using various aluminizing treatments : low and high activity cements, pack and vapor phase coatings. Their metallurgical structure has been investigated with a special emphasis on the repartition of the various metallic elements throughout the coating section. During a first step, aluminizing of the palladium rich underlayer takes place, followed by simultaneous diffusion of nickel and aluminum through this first aluminized layer. Palladium concentration profiles - which significantly differ when using L.A. or H.A. cements - provide qualitative indications concerning the overall "activity" of aluminum in the aluminizing process. Palladium, if present at a sufficient level, enhances Al diffusion in the beta phase. In the case of L.A. processes, a consequence of this increase of Al diffusion flux is the location of NiAl reaction zone inside the coating.



© EDP Sciences 1993