Erosion-corrosion behavior of Ni-20Cr-4Fe and Ni-20Cr-4Fe-7Mo under fluidized-bed biomass boiler conditions

The erosion-corrosion rate of the Mo-free alloy decreased over time because of a reduction in the erosion rate of the oxide scale associated with the transition of the scale from Ni-rich to Cr-rich. In contrast, the Mo-containing alloys displayed accelerated erosion-corrosion because of the repeated erosion of Ni-rich oxide layer and spallation of the oxide scale. The volatilization of Mo oxychloride resulted in the formation of an inner porous oxide layer which results in enhanced spallation of the oxide scale by the impact of sand particles. These volatilization and spallation processes were found to enhance the erosion-corrosion of Mo-containing alloys.