应变速率对Ti425钛合金油气管应力腐蚀的影响

Effect of Strain Rate on Stress Corrosion Cracking of Titanium Alloy Ti425 for Oil and Gas Pipes

通过电化学测试、浸泡试验和慢应变速率试验,研究了Ti425钛合金在模拟油气井环境中的腐蚀行为及应变速率对Ti425钛合金应力腐蚀开裂的影响。结果表明:Ti425钛合金具备再钝化性能,腐蚀电流密度较小(数量级为10^-7 A/cm^2),阻抗较大(数量级为105Ω·cm^2),表面只发生轻微点蚀,且浸泡时间越长,点蚀越严重;当应变速率从10^-6 s^-1升高到10^-3 s^-1,钛合金的屈服强度、抗拉强度、断后伸长率和断面收缩率均增大,断口韧窝特征更加明显,二次裂纹减少,应力腐蚀敏感指数降低。

The corrosion behavior and the effect of strain rate on stress corrosion cracking of titanium alloy Ti425 in simulated environment of oil and gas well were studied by electrochemical measurement,immersion test and slow strain rate test.The results show that Ti425 titanium alloy had repassivation property,low corrosion current density(in magnitude of 10^-7 A/cm^2)and high impedance(in magnitude of 105Ω·cm^2).Meanwhile,slight pitting corrosion was found on the surface of Ti425 titanium alloy,and the longer the immersion time held,the more serious the pitting corrosion was.When the strain rate was changed from 10^-6 s^-1 to 10^-3 s^-1,the yield strength and tensile strength,percentage elongation after fracture and percentage reduction of area increased,the dimple feature of fracture was more evident,meanwhile the secondary crack and the stress corrosion sensitivity index were all reduced.