Hot Corrosion Behavior of a High Velocity Arc-Sprayed Fe-Cr-B-C Coating

摘要

A Fe-Cr-B-C coating was prepared by electric arc spraying process to prevent the boiler tubes from hot corrosion at elevated temperatures. A hot corrosion resistance test was conducted in a mixed molten salt of Na2SO4 and K2SO4 (7:3) at 700 °C for a total period of 156 h. The microstructure and phases of the coatings before and after exposed to the hot corrosion were investigated by scanning election microscopy (SEM), optical microscopy (OM) and X-ray diffraction (XRD). The hardness and porosity were analyzed. The hot corrosion behavior of the coatings was examined by the measurement of corrosion mass gain and the observation of corrosion morphology. The results show that some splats of particles are formed on flat substrate surfaces and the coatings have a dense typical layer structure of electric arc thermally spraying deposits. Some amorphous phase exist in the coating. The coatings have an excellent resistance to hot corrosion. The formation of oxides of chromium on the exposed surface may be contributing better resistance to hot corrosion. The corrosion of the coatings follows the oxidation and sulfidation mechanism.