Hot corrosion behavior of Cr2AlC MAX phase and CoNiCrAlY compounds at 950 °C in presence of Na2SO4+V2O5 molten salts

Abstract

In this research, a high-purity Cr2AlC MAX phase sample was prepared via spark plasma sintering (SPS) method with the hot corrosion behavior investigated in the presence of Na2SO4+V2O5 molten salts at 950 °C. Also, the hot corrosion resistance of this MAX phase was compared with a hot corrosion-resistant SPS-processed CoNiCrAlY sample. The results of the hot corrosion test after 30 h revealed that the MAX phase sample has better hot corrosion resistance compared to CoNiCrAlY sample. According to the results, corrosion kinetics of Cr2AlC sample followed near-cubic law with diffusion occurring along the grain boundaries. On the other hand, CoNiCrAlY sample followed parabolic kinetics where the diffusion of reactants occurred through the oxide scale. The results indicated that in the Cr2AlC sample, upon exposure time prolongation, a dense and uniform Cr-rich alumina layer was formed in the surface and Cr7C3 phase was created as a sub-layer, while in the CoNiCrAlY sample the oxide layer contained Al2O3 and porous spinel oxide phases. In the CoNiCrAlY sample, a considerable volume change and stress occurred during the non-uniform growth of spinel oxide causing the formation of defects such as microcracks which deteriorate its hot corrosion resistance.