HOT CORROSION BEHAVIOR OF Ni-BASED SUPERALLOY WITH HIGH Cr CONTENTS—PART Ⅱ. MECHANISM OF HOT CORROSION BEHAVIOR

Based on the experimental results in the previous paper, the mechanism of the hot corrosion behavior of alloy system Ni-16Cr-9Al-2W-lMo-4Co-(0~4)Ti-(0~4)Ta-(0~4)Nb (in at%) is investigated. In the Ti and Nb-rich comers, hot corrosion is controlled by the basic fluxing mechanism, and a dense and protective surface scale is formed which results in the better hot corrosion resistance for the alloys in these regions. While in the Ta-rich comer, the basic and acidic mechanisms function alternatively, which results in the catastrophic corrosion by forming the porous and non-protective scale, so the alloys in this region show poor hot corrosion resistance. In addition, the concept of "effective chromium content" seeraed to give a correct prediction of the hot corrosion resistance of such alloy systems.