Abstract
The selection of boiler tube materials in the elevated temperature areas of energy producing systems such as fluidized bed combustors (FBCs) is based on the material wastage rates in combined erosion-corrosion environments. Laboratory erosion-corrosion experiments at low elevated temperature (300°C) and low impact velocity (2.5 m/s) were carried out on AISI 1018 carbon steel and sprayed coating specimens. Angular silica quartz particles of 742 μm were the erodent material for testing three different impact angles of 30°, 45°, and 90° under generally oxidizing conditions for exposure periods up to 96 hours.
Material wastage rates were determined from thickness loss measurements of specimens. The morphologies of the specimens were examined by scanning electron microscopy (SEM). The testing showed that some differences existed in the material wastage mechanisms and behavior of steel coatings when low impact velocity was applied. For angular dependence of erosion rate, all coatings exhibited ductile behavior as demonstrated by higher wastage rates at shallow impact angles than that at steep impact angles. The erosion-corrosion resistance of coatings was found to be related to their composition and microstructure rather than to their hardness.
