| Summary: | 博士 === 國立臺灣科技大學 === 機械工程系 === 92 === The hot corrosion of three boiler materials (containing SB450, 2.25Cr-1Mo and 9Cr-1Mo) with 2 mg/cm2 NaCl or coating mixtures of various NaCl/Na2SO4 ratios in a combustion furnace and an electric furnace at 750℃ and 850℃ were studied. The results indicate that the higher the temperature and water vapor in the atmosphere is the more severe in metal loss in pure NaCl deposits. Moreover, water vapor contributed to higher SO2 concentrations by suppressing the NOX formation in the gas produced. Therefore, alloys suffer sulfidation more seriously in an atmosphere that contains water vapor than in one obtained by burning diesel oil; it thus deteriorates more rapidly, however, the atmosphere of the electric furnace was in a steady-state that can make more serious corrosion, but the reason of a lower metal loss of combustion furnace, which was the corrosion source carried away by the combustion gas from the specimens.
Furthermore, there was almost can find the sulfidation effects on the scales when burning with sulfur contained of fuel. It was also found that there was no internal attack of the three alloys which were tested in the combustion furnace, but it can be found that there was internal attack of 2.25Cr-1Mo(750℃) and 9Cr-1Mo(850℃) with salt mixtures in the electric furnace. Accordingly, the order of the resistance of the three alloys was 9Cr-1Mo, 2.25Cr-1Mo, and SB450.
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