Corrosion and Erosion Resistance Thermal Spray Coating of Fe-Si Intermetallics

A gas-atomized Fe₂Si intermetallic powder has been newly developed to protect water wall tubes against severe sulfidation corrosion and erosion in coal-fired boilers. The composition in the developed powder was determined due to its relatively low melting point and combination of inexpensive elements. This powder was evaluated in laboratory tests, including deposition performance test, corrosion test and erosion test. The powder showed high deposition efficiency by both HVOF and air-plasma spraying (APS) despite its high hardness. The corrosion test result demonstrated that the coatings of the powder almost equal sulfidation resistance to conventional 50Cr-50Ni coating under the condition simulating an actual combustion-gas environment of low NOx boiler. In addition, high temperature erosion test results also indicated the APS coating of the developed powder with additional boron content had more erosion resistant than conventional CrC-NiCr coating.