The corrosion-induced microstructure changes associated with the successive stages of damage of the protective layers on nickel-base alloys have been studied metallographically up to complete layer penetration. The microanalytical investigations performed on the distribution of the alloying elements show increased contents of chromium and sulphur in the corrosion attack front zone. However, the microstructure of the diffusion zone, enriched with molybdenum, tungsten and chromium, remains practically unchanged. Attempts at regeneration of the corrosion-worn protective layers of the blades by removing the corrosion products and remnants of the coating with a subsequent new layer deposition have been also described. Two methods of blade recoating are presented in the paper: (a) chemical-vapour-deposited chromoaluminizing either in low- or high-activity processes with the analysis of the effect of processing parameters on the layer microstructure and properties for guide vanes and (b) diffusion annealing of the sprayed silicoaluminizing suspension for rotating blades. The purpose of regeneration is to regain the initial properties of the blades after a period of service. Some of blades formerly rejected for their inadequate structure or defects in the protective layer would be also regenerated in this way. The criteria of surface quality assessment and verification of the blades in successive stages of surface coating regeneration have been worked out.
Corrosion damage and regeneration of aluminide coatings on aircraft turbine blades
Korrosionsschaedigung und Wiederherstellung von Aluminiumlegierungsueberzuegen auf Turbinenschaufeln von Flugzeugen
Materials Science and Engineering, Part A ; A120/121 , 1-2 ; 407-412
1989
6 Seiten, 7 Bilder, 8 Quellen
Aufsatz (Zeitschrift)
Englisch
KORROSIONSSCHUTZSCHICHT , HOCHTEMPERATURSCHUTZSCHICHT , KORROSIONSSCHUTZ , MIKROGEFUEGE , KONZENTRATIONSVERTEILUNG , HOMOGENISIERUNGSGLUEHEN , DIFFUSION , KORROSIONSMECHANISMUS , SCHICHTABLOESUNG , ABPLATZEN , ALUMINID , TURBINENSCHAUFEL , FLUGZEUG , SCHUTZUEBERZUG , SCHADENANALYSE , CHEMISCHES AUFDAMPFEN , REPARATUR , INSTANDHALTUNG , BESCHICHTUNGSVERFAHREN , ALUMINIEREN , INTERMETALLISCHE VERBINDUNG , SPRITZBESCHICHTEN , HAFTFESTIGKEIT
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