Abstract
The hot-corrosion behavior of Ti-50Al, Ti-48Al-2Cr-2Nb, and Ti-50Al-10Cr alloys was investigated in (Na, K)(2)SO4 and Na2SO4+NaCl melts. TiAl intermetallics showed much better hot-corrosion resistance in (Na, K)(2)SO4 at 900 degrees C than the Ni-base superalloy K38G. Two types of corrosion products formed on Ti-50Al: some areas were covered with a continuous Al2O3 scale, whereas other areas formed a mixed Al2O3+TiO2 scale; TiS existed at the scale-alloy interface. A mixed Al2O3+TiO2 scale formed on Ti-48Al-2Cr-2Nb, and no sulfide was found beneath the scale. An adherent Al2O3 scale, however, formed on Ti-50Al-10Cr, which provided excellent hot-corrosion resistance. All three alloys suffered severe hot corrosion in Na2SO4+NaCl melts at 850 degrees C. A mixed Al2O3+TiO2 scale formed on all three alloys and many voids and pits existed in the scale-alloy interface. The hot-corrosion mechanisms are discussed.
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