满洲里土壤模拟溶液温度对X80管线钢应力腐蚀行为的影响

Effect of Temperature on the Stress Corrosion Behavior of X80 Pipeline Steel in Simulated Manzhouli Soil Solution

采用交流阻抗技术、动电位极化技术和慢应变速率拉伸试验研究了X80管线钢(X80钢)在不同温度的满洲里土壤模拟溶液中的应力腐蚀开裂(SCC)行为,并用扫描电镜观察了不同温度下的宏观断口和微观断口形貌。研究结果表明:X80钢在5℃和35℃溶液中均表现出很高的SCC敏感性;在温度大于50℃的溶液中,X80钢的SCC敏感性随溶液温度升高而持续增加。出现这种现象的原因是:在5℃溶液中,溶液中溶解大量的CO_2,CO_2水解出的H+致使X80钢的SCC敏感性上升;在35℃溶液中,阴极析出大量H_2,H_2与位错交互作用导致X80钢SCC敏感性提高;当溶液温度升高到50～80℃时,X80钢表面形成了致密的腐蚀产物膜,产物膜阻碍了位错扩展,X80钢脆性增加,即X80钢的SCC敏感性随温度升高而增加。

Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization technique and slow strain rate testing (SSRT) are employed to study the stress corrosion cracking (SCC) behavior of X80 pipeline steel (X80 steel) in simulated Manzhouli soil solution under different temperatures, and macrofracture and microfracture morphologies under different temperatures are observed by scanning electron microscope (SEM). The results show that high SCC sensitivity of X80 steel is observed at 5 ℃ and 35 ℃ solutions, and the SCC sensitivity of X80 steel increases with temperature increase when the temperature is above 50 ℃. The reasons explaining this phenomenon are as follows: in the 5 ℃ solu-tion, a large amount of CO2 is dissolved in the solution, which creates many H + and then makes X80 steel's SCC sensitivity arise. In the 35 ℃ solution, the cathode precipitates a large amount of H2, and H2 interacts with dislocation, resulting in X80 steel's SCC sensitivity increase. When the solution temperature ranges from 50 to 80 ℃, a dense corrosion film will form on the surface of X80 steel, which hinders the dislocation expansion, thus increasing X80 steel' s brittleness, namely the SCC sensitivity of X80 steel increases with the increase of temperature.