材料期刊网

目的 研究纳米Y2 O3 预处理对T91钢抗水蒸汽氧化性能的影响,分析稀土元素作用的机理及长期氧化后的失效机制. 方法 采用将Y2 O3、铝粉、粘结剂制备成料浆涂覆于T91钢表面,并在720 ℃水蒸汽中预处理48 h. 预处理样品和空白样品同时置于在700 ℃高温水蒸汽中氧化,获取循环氧化动力学曲线并进行对比,检验预处理对提高材料抗高温水蒸汽腐蚀的效果. 对氧化的样品采用XRD、SEM/EDS对氧化物结构、形貌、成分进行分析. 结果 预处理后在样品表面形成了含Y2 O3 的富铬氧化物薄膜. 在高温水蒸汽环境的氧化过程中,试样处理600 h时,质量增加轻微,仅为0. 152 g/cm2. 但在600 h后质量增加明显,预处理膜层逐渐退化,表面出现Fe2 O3 突出物. 空白样在腐蚀初期即明显增加,氧化70 h后,质量增加达12. 17 mg/cm2 ,氧化过程中可见氧化产物的剥落,氧化膜附着力差. 结论 纳米Y2 O3预处理可提高T91钢抗水蒸汽氧化性能,但随着氧化时间延长,富铬氧化膜将逐渐退化.

Objective To investigate the effect of nano-Y2 O3 pretreatment on oxidation resistance of T91 steel in high-tempera-ture water vapor environment. The action mechanism of rare earth elements and the failure mechanism after long-term oxidation were also discussed. Methods The surface of T91 steel was coated by a slurry composed of Y2 O3 , aluminum powder and a binder.Then the coated sample was treated in water vapor environment at 720 ℃ for 48 h. Cyclic oxidation test of the pretreated samples and bare sample were conducted in water vapor environment at 700℃. The effect of pretreatment on the oxidation resistance of the material in high-temperature water vapor environment was examined by comparison of cyclic oxidation kinetics between the pretrea-ted sample and the bare sample. The composition, structure, morphology of the cyclically oxidized samples were investigated using XRD, SEM and EDS. Results Cr2 O3-rich scale with small amount of Y2 O3 was formed on the surface of the pretreated sample. The pretreated samples showed slight weight gain after 600h oxidation in water vapor environment at 700 ℃. The mass gain was a-bout 0. 152 mg/cm2 at 600 h of oxidation. However, significant mass gain was observed when the oxidation time was longer than 600 hours. The pretreatment scale gradually degenerated during the oxiadation, and some Fe2 O3 grains were observed on the sam-ple surface. For bare sample, significant mass gian was observed at the beginning of the oxidation stage. The mass gain was about 12. 1 mg/cm2 after oxidation for 70 h. Spallation of the oxide was observed during the oxidation, indicating poor adhesion of the scale to substrate. Conclusion Nano-Y2 O3 pretreatment could obviously improve the water vapor oxidation resistance of T91 steel. However, the Cr2 O3-rich scale would degrade gradually during the oxidation in water vapor environment at high temperatures.