T95油井管在酸性油气田环境中的应力腐蚀开裂行为及机制

Stress Corrosion Cracking Behavior of T95 Oil Well Pipe Steel in Sour Environment

通过光学显微镜和透射电镜分析T95钢第二相及合金元素对材料抗应力腐蚀开裂(SCC)性能影响。在不同酸性pH值条件下,结合动电位极化方法、恒载荷拉伸以及显微镜微观分析等方法,研究了T95油井管钢的应力腐蚀行为,并探究了其裂纹发生机制。结果表明,T95钢的SCC行为对pH值敏感,在pH值2.8~4.5之间存在一个临界值,溶液p H值低至2.8及以下时T95钢的SCC敏感性高;腐蚀溶液pH值降低,应力环断裂时间缩短,T95钢SCC敏感性增加。随着溶液pH值降低,环境输入H+电流(IH+)增加,阴极反应加强,促进氢致开裂;H+在裂尖聚集,促进裂纹扩展,加强阳极溶解。T95钢的裂纹扩展受到阳极溶解和氢致开裂机制协同作用。

The effect of second phases and alloying elements on stress corrosion cracking(SCC)behavior of oil well steel T95 in sour H2 S environments was investigated by means of electrochemical polarization measurement,constant tensile test,optical microscope and transmission microscope.Results showed that solutions of pH=2.3 and pH=2.8 were SCC sensitive environment to T95.With the decreasing pH,cracking time of the prestressed rings decreased,namely,the SCC sensitivity of T95 increased.With the decrease of pH,the IH+(input current from the environment)increased,while the cathode reaction was enhanced,as a consequence,the hydrogen induced cracking(HIC)occurred.Meanwhile,the aggregation of H+on the crack tip might promote the crack expansion,accordingly,the anodic dissolution was enhanced.The crack propagation was controlled simultaneously by anodic dissolution(AD)and hydrogen embrittlement(HE)in the solutions of pH=2.3 and pH=2.8.