| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 87 === Abstract
The high-temperature corrosion behavior of the three Fe base alloys, containing Fe-29.1Mn-8.98Al-0.75C (Fe-Mn-Al), STP-A26 alloy (A26), and 310 heat-resistant steel (310SS) has been studied at 750℃ in air with 2 mg/cm2 mixtures of various NaCl/Na2SO4 ratios. The results showed that the three alloys with 100% Na2SO4 deposit corroded as similar to pure oxidation in air. However, NaCl acts as the predomiant corrosion species for the three alloys. In the case of both A26 and 310SS, the most severe corrosion was taken place at the 75/25 wt% NaCl/Na2SO4 ratio, while the most severe corrosion for Fe-Mn-Al was at the 100% NaCl deposit.
The AlN started to form on the scales of the Fe-Mn-Al alloys as the NaCl deposit is over 50 wt% and its amount increased with increasing NaCl deposit. The selective oxidation of Mn due to the supply chlorine from NaCl deposits causes a porous substrate of the second ferrite containing relatively high activity of Fe and Al. In addition, the formation of manganese oxides also increased the partial pressure of nitrogen in air, so that AlN formed on the substrate and reduced the corrosion resistance of the Fe-Mn-Al alloy.
The 310 had much chromium and nickel by compared with STP A26. The more chromium enhanced the oxidation resistance of alloy and reduced the depth of metal loss in the 100%Na2SO4 environment. However, the nickel in alloy reacted with sulfate formed nickel sulfide. Because of the eutectic reaction of nickel and its sulfide, the 310 showed the great deviation form simple oxidation of the three alloys in this environment.
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