EFFECT OF SOME SODIUM-SALTS COATINGS ON THE HIGH-TEMPERATURE OXIDATION OF NIMONIC-80A ALLOY AT 1173 K

The effects of some sodium salts, namely Na2SO4, NaCl, NaNO3 and Na2CO 3 coatings, on the high-temperature oxidation behaviour of Nimonic-80A (N-80A) alloy at 1173 K in a slow current of air are presented. The o xidation kinetics and effects of salt deposition on the N80A alloy wer e investigated. The alloy is more severely attacked by NaCl than by Na 2SO4, due to the formation of volatile chlorides. NaNO3- and Na2CO3-in duced alloy seem to be more aggressive than Na2SO4 and NaCl due to the evolution of nitrogeneous and CO/CO2 gases respectively. The scale mo rphologies were determined on the basis of X-ray diffraction analysis and scanning electron microscopic techniques.