Nondestructive Microstructural Characterization of Superduplex Stainless Steel by Double Loop Electrochemical Polarization Reactivation Portable Test

Superduplex stainless steels (SDSS) are frequently employed in the petrochemical industries where is required high mechanical strength, toughness, and corrosion resistance. However, these properties can be affected by deleterious phases formation due thermomechanical processes applied in the field during pipes and vessels construction. This work propose the nondestructive microstructural characterization of deleterious phases precipitated in SDSS isothermally treated in 800 and 850ºC using portable double loop electrochemical polarization reactivation tests (DL-EPR). The results obtained in this nondestructive test are quite close to those obtained by conventional test, and can be correlated with the amount of deleterious phases precipitated. It can be concluded that the microstructural degradation of superduplex stainless steel can be evaluated by portable DL-EPR test with slow sweep rates, using a special cell and a proper electrolyte at room temperature.

超级双相不锈钢（Superduplex Stainless Steels, SDSS）凭借优异的机械强度、韧性与耐腐蚀性能，被广泛应用于石油化工行业。然而，在管道与容器的制造过程中，现场采用的热机械加工工艺会诱发有害相析出，进而对上述综合性能产生不利影响。本研究采用便携式双环电化学动电位再活化试验（Double Loop Electrochemical Polarization Reactivation Tests, DL-EPR），对在800℃与850℃下等温处理的SDSS中析出的有害相开展无损显微组织表征。结果显示，该无损检测方法所得结果与常规试验结果高度吻合，且可与析出有害相的含量建立相关性。研究表明，通过采用慢扫描速率、专用电解池与适宜电解液，在室温条件下开展便携式DL-EPR试验，即可实现超级双相不锈钢显微组织劣化程度的有效评估。