低铬抗硫套管的H_2S/CO_2腐蚀行为研究

通过高温高压及H2S应力腐蚀开裂(SSC)实验,采用SEM、EDS、XRD和TEM技术,研究3Cr110S在模拟环境中的H2S/CO2腐蚀行为。结果表明:在模拟H2S/CO2高温高压腐蚀环境中,H2S腐蚀占主导作用,3Cr110S的均匀腐蚀速率为0.1272 mm/a,局部腐蚀轻微,试样表面腐蚀产物为FeS;在施加应力为72%、80%的最低屈服强度时,3Cr110S试样均未发生应力腐蚀开裂,具有良好的抗SSC性能;3Cr110S回火索氏体组织的条束之间位相差大,铬元素在晶界及晶内以粒状碳化物析出、位错纠结、弥散分布碳化物的位错定扎对SSC裂纹扩展起着良好的阻碍作用。

Study on H2S/CO2 Corrosion Behaviors of Low-Cr Acid Resistant Casing Steel

H2S/CO2 corrosion behaviors of 3Cr110S steel were studied with high temperature and high pressure and H2S stress corrosion cracking (SSC) test by use of scanning electron microscope (SEM), energy disperse spectroscopy (EDS), X-Ray diffraction (XRD) and transmission electron microscope (TEM). The results show: Under the simulated high temperature and high pressure H2S/CO2 corrosion conditions, H2S electrochemical corrosion dominates the corrosion course, and the uniform corrosion rate of 3Cr110S steel is 0.127 2 mm/a, furthermore, the local corrosion is very slight. When the applied stress is 72% and 80% actual yield strength (AYS), all test specimens of 3Cr110S steel have not been found cracked which reveals the superior SSC resistance. The larger orientation difference between lath microstructures of 3Cr110S tempered sorbite micro-structure, granular carbide about Cr precipitating at the grain boundary or in crystal grain, dislocation tangle as well as dislocation pinning of the dispersion carbonide, all of those hinder severely SSC cracks to propagate.