Kinetics of High Temperature Oxidation and of Chromia Volatilization for Chromium Carbides-containing Alloys
Résumé
Resistance of superalloys against several contraints (mechanical deformation, corrosion by molten salts or glasses, oxidation…)
-> external stoechiometric oxide layer
Al2O3: efficient against oxidation, Cr2O3: efficient against oxidation and corrosion
Cr2O3 + 3/2 O2 -> 2 CrO3 (gaseous): Problem of chromia volatilization when T > 1000°C : the real damage supported by the material can be minimized
Superalloys strenghtened with carbides are often chromia-forming: Necessity to precise both oxidation and chromia volatilization rates for T > 1000°C
xidation of superalloys: Oxidation of Ni30CrxC alloys follows a parabolic law; Oxidation rate depends on carbon content: Kp and Kv increase with %wtC
New mathematical model to determine Kp and Kv:
* Drawing mdm/dt versus –m allows to determine directly both Kp and Kv
* Kp and Kv values were verified twice. They describe the real HT phenomenon.
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