| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 87 === The purpose of this study is to investigate the NaCl-induced hot corrosion behavior of five commercial steels (containing STPA24, STPA26, 253MA, 310SS, and 353MA). The effects of NaCl deposits and environments on the hot corrosion of the steels were also evaluated by means of morphology observation, depth of attack, and quantitative analysis methods.
The results showed that: The corrosion morphology of Fe-Cr base alloys (STPA24 and STPA26) show the metal loss only, however, the Fe-Cr-Ni base alloys (253MA, 310SS and 353MA) showed not only metal loss but with a subscale attack. Except STPA26, the corrosion of alloys increased with increasing the amounts of NaCl deposits. The higher the partial pressure of oxygen the more severe the metal loss of alloy. In addition, for 310SS, the effect of the corrosion time at high temperature on the depth of subscale attack of 310SS is much significant as compared to the effects of corrosion environments.
As alloys immerged in molten NaCl, the metal loss resulted from metal dissolving. Since Cr has the most tendency to cause the mental dissolving, the metal loss of 310SS which contains the highest amounts of Cr is more than those of STPA24 and STPA26. As the Ar gas purges into the corrosion environments, the partial pressures of oxygen reduced, which cause a significant reduction of the metal loss for the STPA24 steels.
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