用于高含硫气田的镍基合金管材服役后局部腐蚀的成因

发布时间：2018-10-19 17:56

【摘要】：为了研究镍基合金Incoloy 825(UNS NO8825)管材在高含硫气井井口服役后内表面局部腐蚀坑的形成原因及其服役状况,截取并纵剖服役1年后的带有焊接接头管材进行检查。通过扫描电镜观察了服役后的管体、焊接接头、焊接热影响区和腐蚀晶界横截面的微观形貌,并结合能谱仪对以上区域进行了元素分析。结果表明:(1)服役后Incoloy 825合金管材表面发生了晶间腐蚀且局部腐蚀坑内的晶间腐蚀更为严重,但却未发现硫化物腐蚀产物沉积;(2)焊接热影响区晶粒长大且晶界有析出相,但未发现局部腐蚀;(3)Incoloy 825合金管材内表面发现的点蚀为酸洗钝化处理时过酸洗造成的;(4)在服役过程中,Incoloy 825合金管材和焊接接头腐蚀轻微;(5)虽然过酸洗导致了管材内表面的局部腐蚀,但经酸洗钝化处理后的钝化膜则具有较强的耐蚀能力;(6)服役时的高温高压酸性环境不会对已酸洗钝化的Incoloy 825合金管材造成侵蚀,也不会导致局部腐蚀扩展。
[Abstract]:In order to study the formation of local corrosion pits on the inner surface of nickel-based alloy Incoloy 825 (UNS NO8825) pipes after service at the wellhead of high sulfur gas wells and their service conditions, the welded joint pipes with welded joints after 1 year of service were intercepted and longitudinal dissected for inspection. The microstructure of the tube body, welded joint, weld heat affected zone and corrosion grain boundary cross section after service were observed by scanning electron microscope (SEM), and the elemental analysis of the above regions was carried out by means of energy dispersive spectrometer (EDS). The results showed that: (1) the intergranular corrosion occurred on the surface of Incoloy 825 alloy tube after service, and the intergranular corrosion in the local corrosion pit was more serious, but no sulfides corrosion products were found, (2) the grain size grew and the precipitated phase occurred in the grain boundary in the HAZ. But no local corrosion was found; (3) the pitting corrosion found on the inner surface of Incoloy 825 alloy pipe was caused by over acid pickling during acid pickling and passivation treatment; (4) during service, the corrosion of Incoloy 825 alloy pipe and welded joint was slight; (5) although the over acid pickling resulted in the inside of the tube Local corrosion of the surface, However, the passivation film after pickling and passivation has a strong corrosion resistance. (6) the high temperature and high pressure acid environment during service will not cause corrosion on the Incoloy 825 alloy tube which has been pickled and passivated, nor will it lead to local corrosion expansion.
【作者单位】：中国石油大学(北京)理学院材料科学与工程系;
【基金】：国家自然科学基金项目“Fe-Cr合金表面双层钝化膜离子迁移行为的第一性原理研究”、“镍基、铁镍基合金油井管第二相的演变及其对耐蚀性的影响”(编号:51301200、51134011)
【分类号】：TE980;TG178

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