为了探究低活化9Cr氧化物弥散(9Cr-ODS)钢在设计服役环境下的氧化行为及机理，通过模拟聚变堆高温高压循环水腐蚀实验，研究了其在聚变堆设计冷却水中的腐蚀行为，并与中国低活化马氏体(CLAM)钢进行对比，阐释了腐蚀过程中表面及截面微观结构的演化和氧化产物的形成与转变过程。结果表明，在325 ℃、15.5 MPa的静态高温高压水和动态高温高压水(温度25 ℃、压力15.5 MPa、流速5 mL/min)中，9Cr-ODS钢的腐蚀增重和氧化膜厚度均比CLAM钢低。在静态水中腐蚀时，2种材料的腐蚀产物均为外层为颗粒状的Fe₃O₄、内层为连续的富Cr、Fe 的尖晶石的双层结构；随腐蚀时间从200 h增加至1000 h，氧化物颗粒尺寸和氧化膜厚度逐渐增加；然而在动态水中，2种钢的腐蚀增重及氧化膜厚度反而降低，其中CLAM钢外层氧化物的种类保持不变，但9Cr-ODS钢中除Fe₃O₄外还有少量Fe₂O₃生成。在相同腐蚀条件下，弥散的纳米氧化物、细化的晶粒以及较高的基体O含量对ODS钢耐腐蚀性能产生了积极作用，促进了保护性氧化膜内层的形成，同时也降低了腐蚀增重速率，使得9Cr-ODS钢具有比CLAM钢更优异的耐腐蚀性能。

The China fusion engineering test reactor is a bridge between the international thermonuclear experimental reactor and future fusion demonstration reactors. The harsh service environment of the fusion reactor, including high heat flow density, strong neutron irradiation, and high temperature and high pressure coolant corrosion, demands higher requirements on structural materials than conventional nuclear energy structural materials. Low activation oxide dispersion-strengthened (ODS) steels, which are developed based on reduced activation ferritic/martensitic steels, are considered as promising candidate fusion reactor structural materials because of their high creep strength and excellent resistance to irradiation. In this study, 9Cr-ODS steel prepared by mechanical alloying (MA) and Chinese low activated martensitic (CLAM) steel prepared by vacuum smelting were selected because of their excellent mechanical properties and superior radiation tolerance. The main difference between the two steels is the grain size: the average grain size of the 9Cr-ODS steel is 200-500 nm, whereas that of CLAM steel is 10-20 μm. Furthermore, the 9Cr-ODS steel was added with Y₂O₃ during MA, which improved its mechanical properties and thermal stability. Corrosion experiments were conducted in static and dynamic (flow rate of 5 mL/min) ultrapure water at 325 ^oC and 15.5 MPa. Ultrapure water had an electrical conductivity of 0.1 μS/cm and a dissolved oxygen content of 10 × 10^-9. The exposure time for both steels were set as 200, 500, and 1000 h. Results indicated that under static and dynamic conditions, the corrosion mass gain and oxide film thickness of the 9Cr-ODS steel were less than those of the CLAM steel. Under static conditions, the corrosion product of both materials exhibits a double-layer structure with granular Fe₃O₄ in the outer layer and continuous Cr- and Fe-rich spinel in the inner layer. As the exposure time increased from 200 h to 1000 h, the size and thickness of the oxide particles gradually increased. However, under dynamic conditions with a flow rate of 5 mL/min, the surface of the 9Cr-ODS steel formed not only Fe₃O₄ but also a small amount of Fe₂O₃, while the type of oxide in the outer layer of the CLAM steel remains unchanged. In contrast to the static condition, both steels exhibited decreased corrosion mass loss and oxide film thickness because of the dynamic water scouring effect and the buildup of H₂ on the surface caused by water decomposition through oxidation. Overall, under same corrosion conditions, the presence of dispersed oxides, grain refinement, and a high matrix oxygen concentration positively enhanced the corrosion resistance of the 9Cr-ODS steel. This enhancement facilitated the formation of a protective inner oxide layer and reduced the corrosion mass loss rate, thereby demonstrating the superior corrosion resistance of the 9Cr-ODS steel under high temperature and high pressure water environments compared with the CLAM steel.