Corrosion and Erosion Resistant Thermal Spray Coatings of Fe-Si Intermetallics

This study evaluates Fe-Si intermetallic powders as an alternative to powders currently used to coat furnace walls in pulverized coal fired boilers. The developed powder mainly consists of Fe₂Si, which has a relatively low melting point among iron silicides. The powders were deposited on CrMo steel substrates by HVOF and atmospheric plasma spraying and the resulting coatings were subjected to corrosion and erosion testing. Under conditions simulating the operating environment in a low NO_X boiler, the HVOF sprayed Fe-Si coatings exhibited sulfidation resistance nearly equal to that of Cr-Ni layers, and in high-temperature erosion tests, the APS intermetallic coatings with boron additions were found to be more erosion resistant than conventional Cr₃C₂-NiCr coatings.