目的 以高放废液封装容器材料309S奥氏体不锈钢为研究对象，通过N、Nb联合添加改善不锈钢在Cl^-环境中的耐蚀性能，并探究N、Nb元素对不锈钢耐蚀性能的影响机理。方法 采用扫描电镜、X射线衍射、形状测量激光扫描系统、X射线光电子能谱等手段，对不锈钢的微观组织及钝化膜成分进行分析，从击穿电位、极化电阻及腐蚀形貌等方面揭示了N、Nb元素对不锈钢耐腐蚀性能的影响机理。结果 N的添加可以促进含Nb钢中耐蚀的Nb(C, N)析出以及难溶的Nb2O5腐蚀产物形成。同时，部分N转化为NH3/NH4⁺，提高局部pH，有利于表面再钝化。因此，N、Nb联合添加的309S不锈钢展现出优异的耐蚀性能。相比商用309S不锈钢，添加0.17%(质量分数)N和0.45%(质量分数)Nb的不锈钢在3.5%(质量分数)NaCl溶液中击穿电位由0.20 V提升至0.96 V，自腐蚀电流密度从2.529×10^-7 A/cm²减小到0.793×10^-7 A/cm²。6%FeCl3-0.16%HCl(质量分数)溶液浸泡腐蚀120 h后，N、Nb联合添加的不锈钢点蚀坑数目最少，平均表面粗糙度(Sa)、最大点蚀坑宽度(Wmax)和最大点蚀坑深度(Dmax)均最小，展现出良好的耐蚀性能;仅添加Nb不添加N的不锈钢其击穿电位略低于309S不锈钢，Sa最大，点蚀坑向纵深方向扩展严重。结论 N、Nb联合添加能有效抑制点蚀坑的萌生与扩展，显著提高不锈钢耐腐蚀性能，而单独添加Nb效果较差。

309S austenitic stainless steel is one of the candidate materials for the canisters to store high-level waste. However, the corrosion resistance of 309S austenitic stainless steel makes it difficult to meet a design life of 100 years in the groundwater environment containing a Cl-. The corrosion resistance of 309S austenitic stainless steel was improved by adding N and Nb, and the differences in microstructure and corrosion resistance of experiment steel with different N and Nb contents were compared and analyzed. The microstructure and passivation film composition of the stainless steel were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Shape Measurement Laser Microscopy System (SMLMS) and X-ray photoelectron spectroscopy (XPS). The effect of N and Nb on material corrosion resistance was discussed. Electrochemical tests were carried out at the Gamy-Reference 3 000 workstation. A three-electrode system was used as an electrolytic cell. The potentiodynamic polarization curve of the sample was measured by the potentiodynamic method. After the open circuit potential stabilized, the test was performed at a scanning rate of 0.33 mV/s and a test interval of -1.0 to 1.5 V (vs.SCE). The impedance spectrum of the sample was measured by the potentiostatic method. The amplitude was 10 mV, and the test interval was 0.01~100 kHz. ZView fitted the impedance spectrum. The polarization curve results showed that the pitting electricity of 2# and 4# samples increased from 0.20 V of the original 1# sample to 0.50 V and 0.96 V after addition of N and Nb. The impedance spectra showed that the arc of capacitive reactance increased obviously after N and Nb were added. Corrosion loss tests were performed according to ASTM standard G31-72. The sample was cut into 24 mm × 18 mm × 3 mm, and then soaked in a container containing 6wt.% FeCl3-0.16wt.% HCl solution at 35 ℃ for 120 h. During the 120 h soaking period, after sampling, ultrasonic cleaning with 20vol.% HNO3 for 60 min was performed to remove the corrosion products. The surface roughness of 3# stainless steel increased to 4.43 times after corrosion, and the maximum depth of the pitting pit increased by a factor of 1.59. After addition of N and Nb, the maximum width and depth of the pitting pit decreased to 41% and 2%, respectively. The XPS results showed that Nb2O5 passivation film was formed, and Nb(C, N) was precipitated to inhibit the initiation and growth of pitting pits in 309S austenitic stainless steels. N may be involved in forming Nb2O5, which helps stabilize the passivation film. This finding is important for studying the effect of N on the composition of the passivation film. The partial conversion of N to NH4+ to increase the local pH value of the solution jointly improves the ability of stainless steels to resist Cl-, thereby improving the corrosion resistance of 309S austenitic stainless steel. It is proved that the combined addition of N and Nb significantly improves the corrosion resistance of 309S austenitic stainless steel.