9Cr-1Mo钢在含水蒸汽气氛中的氧化行为

研究了9Cr-1Mo(ASME T91)钢在(Ar 10%H_2O)气氛中600℃、650℃和700℃下的高温氧化行为.在恒温氧化10 h过程中,在600℃氧化遵从抛物线规律;而在650℃和700℃氧化则遵从分阶段抛物线规律,且后一阶段的速度常数高于前一阶段的;随着温度的升高,氧化速度明显增大;氧化激活能为157.2 kJ/mol.T91钢氧化时表面形成了多层结构的氧化膜,从外到内依次为Fe_2O_3、Fe_3O_4和(Fe,Cr)_3O_4;钢基体也发生了内氧化,内氧化物为FeO和Cr_2O_3.只有在700℃氧化时没有外层Fe_2O_3形成和内氧化发生.9Cr-1Mo钢氧化后冷却至室温后,氧化膜发生开裂或局部剥落.最外层Fe_2O_3与次外层Fe_3O_4间出现很大的裂隙,Fe_2O_3层容易剥落.同时探讨了9Cr-1Mo钢在含水蒸汽气氛中的氧化机制.

Oxidation characteristic of ferritic–martensitic steel T91 in water–vapour atmosphere

The oxidation behavior of 9Cr-1Mo steel in (Ar+10%H₂O) atmosphere at 600 °C, 650 °C and 700 °C was investigated. During oxidation for 10h the oxidation kinetics followed parabolic law at 600 °C, but two–stage parabolic law at 650 °C and 700 °C, in which the rate constant at the initial stage was higher than that at the second stage. With increasing temperature, the oxidation rate of T91 steel increased significantly. The oxidation activation energy was identified as 157.2 kJ/mol. The oxide scale with three–layer microstructure was composed of Fe₂O₃, Fe₃O₄ and (Fe, Cr)₃O₄ in the order from the top layer to the inner layer. Meanwhile the internal oxidation was also observed, the corresponding internal oxides were Cr₂O₃ and FeO. However, at 700 °C, neither Fe₂O₃ outer layer nor internal oxides formed. The outer layer (Fe₂O₃) had a weak adhesion to the intermediate layer (Fe₃O₄) and easily spalled during cooling from oxidation temperature to room temperature. The oxidation mechanism of T91 in (Ar+H₂O) atmosphere was discussed finally.