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针对不同结构对Fe_3Al合金在湿H_2S-CO_2-Cl~-天然气集输环境中耐蚀性的影响,对未处理、经B_2或DO_3热处理的Fe_3Al试样,遵循ASTM G111-97(2013)和NACE TM 0169/G31-12a标准,试验模拟罗家寨气田实际工况进行全浸均匀腐蚀试验,评估其腐蚀速率;采用XRD表征其物相;采用SEM表征其腐蚀前后表面的微观结构;采用EDS测量并统计分析不同结构位置化学成分的差异。结果表明,Fe-28Al-4Cr合金(原子分数,%)在所模拟罗家寨气田实际工况环境中,经168 h后合金表面形成内层以铝氧化物+铁氧化物为主、外层以铁氧化物+铁硫化物为主的双层腐蚀产物膜,内层膜致密而均匀,但受金属基体表面形貌影响会发生开裂。Fe-28Al-4Cr合金表面DO_3结构比B_2结构Fe含量约低1.75at%,而Al含量约高1.64at%。内层腐蚀产物膜主要构成元素Al含量的不同,使合金表面钝化膜生长行为产生差异,进而影响合金耐蚀性;具体表现为2~24 h内因钝化DO_3处理合金的腐蚀速率下降响应更迅速。在所模拟罗家寨气田实际工况环境中,168 h后Fe-28Al-4Cr合金腐蚀速率趋于稳定,为0.238~0.27 mm/y,均达到了实际工程应用的条件。
According to the influence of different structures on the corrosion resistance of Fe_3Al alloy in wet H_2S-CO_2-Cl ~ - natural gas gathering environment, the un-treated, B_2 or DO_3 heat treated Fe_3Al samples were tested according to ASTM G111-97 (2013) and NACE TM 0169 / G31-12a standard was used to simulate the corrosion of Luojiazhai gas field. The corrosion rate was evaluated by XRD. The microstructure of the surface before and after corrosion was characterized by SEM. And statistical analysis of the differences in the chemical composition of different positions. The results show that the inner layer of Fe-28Al-4Cr alloy (atomic fraction,%) formed in the actual working condition of Luojiazhai gas field after 168 h is dominated by aluminum oxide + iron oxide and the outer layer The double corrosion product film, which is dominated by iron oxide + iron sulfide, has a dense and uniform inner film, but cracks occur due to the influence of the surface morphology of the metal substrate. The DO 3 structure on the surface of Fe-28Al-4Cr alloy is about 1.75at% lower than that of B 2 structure, while the Al content is about 1.64at% higher. The content of Al, which is the main constituent of the inner corrosion film, causes the difference of the growth behavior of passive film on the surface of the alloy, and further affects the corrosion resistance of the alloy. The corrosion rate of the alloy treated with passivation DO_3 is reduced within 2-24 h rapid. The corrosion rate of Fe-28Al-4Cr alloy tends to be stable at 0.238 ~ 0.27 mm / y after 168 h in the actual conditions of the Luojiazhai gas field simulated, all of which have reached the actual engineering application conditions.