FV(520)B不锈钢高温高压条件下硫化腐蚀初始阶段机理研究

Study on Sulfidation Mechanism at Primary Stage of FV( 520) B Stainless Steel at High Temperature and High Pressure

目的研究高温高压条件下FV(520)B不锈钢硫化初始阶段的腐蚀机理。方法在573 K,H2S分压为1.5 MPa条件下制备硫化腐蚀试样,利用XPS,SEM等分析硫化膜成分、元素含量及分布。结果硫化膜为双层膜结构,外层成分为Fe7S8,Fe S2和Ni(1-x)S,内层成分为Fe7S8,Fe S2,Ni(1-x)S和Cr2S3。XPS数据显示Fe7S8,Fe S2中存在Fe2+和Fe3+,且Fe3+平均原子数分数分别为36.53%和35.78%,Ni(1-x)S硫化物中存在Ni2+,Ni3+,且Ni3+的平均质量分数约为32.08%。结论铁镍硫化物的主要缺陷为阳离子缺陷,且缺陷浓度较高,内层中Cr2S3抑制Fe,Ni离子向外迁移,但硫化初期阶段Cr2S3的含量少,抑制作用不明显。

Objective To investigate the sulfidation mechanism of FV（520）B stainless steel at primary stage. Methods The sulfidation specimen was prepared by the exposure of FV（520） B stainless steel to the atmosphere of 1.5 MPa H25 at 300 ℃. XPS and 5EM analysis techniques were applied to investigate the content, the distribution of element and the composition of the sulfide scale. Results The muhilayered sulfide scale was composed of an outer layer of Fe7S8, FeS2 , Ni（1-x） S and a inner layer of Fe7 Ss , FeS2 , Ni（1-x）/S, Cr2S3. XPS data indicated that Fe^3＋ and Fe^2＋ were found in Fe7S8 and FeS2 in all sputtered layers, and the average contents of Fe^3＋ were 36.53% and 35.78% , respectively. Ni^2＋ and Ni^3＋ were also observed in Ni（1-x） S and the content of Ni^3＋ was 32.08%. Conclusion The data analysis demonstrated that the cation vacancy was the predominant defect in ferrous, nickel sulfide and the defect concentrations were high. Outward diffusion of Fe and Ni ions were constrained by Cr2 S3 in the inner layer, but the inhibitory effect was not obvious due to the lack of Cr2S3 in sulfide scale at the primary stage of sulfidation.