The system energy of H atom occupying different positions in Cr2O3 crystal lattice is calculated by adopting the first-principles calculation method based on density functional theory in this paper. The results indicate that the most stable position of H atom in Cr2O3 crystal lattice locates at the bilateral positions of the center of the unoccupied O octahedral interstice. The reason resulting in this situation is analyzed by comparing the change of Cr2O3 lattice distortion and density of states in Cr2O3_H system when H atom locates at different positions in octahedral interstice. The diffusion activation energy of H atom is 0.73 eV,which is determined by seeking the diffusion path and transition state of H atom in Cr2O3 crystal lattice. The effective attempt frequency of H atom in Cr2O3 crystal lattice is also calculated by using molecular dynamics. Combining with diffusion activation energy data,the diffusion coefficient of H atom in Cr2O3 crystal is determined.
With the exploitation of high sour and deep oil well in china,the corrosion medium containing CO 2,H 2 S,Cl-and organic acid threaten the safety of oil equipment and tube steel severely.In this article,many experiments,including corrosion tests,tensile tests,hydrogen concentration measurement tests and SEM examinations,were performed to investigate the effect of H 2 S partial pressure and loading stress on the mechanical property of oil tube steel P110S in high temperature and high pressure environment containing H 2 S/CO 2.The tensile strength and yield strength during fracture process of P110S steel were obtained experimentally and the fracture morphology was analyzed by SEM.The results indicate that both tensile strength and yield strength decreased after corrosion.The damage of tensile strength and yield strength became serious with an increase in H 2 S partial pressure and loading stress.According to the fracture analysis,the fracture mode exhibited quasi-cleavage and dimple mixed fracture,and the area of quasi-cleavage pattern increased with H 2 S partial pressure and loading stress increasing.According to the results of tensile test and hydrogen concentration measurement test,the tensile property degradation is closely associated with diffusible hydrogen concentration of P110S steel in the H 2 S/CO 2 environment.
LI Xiao-dong 1,QI Ya-meng 2,CHEN Chang-feng 2,DONG Xiu-cheng 1 (1.School of Business Administration,China University of Petroleum(Beijing),Beijing 102249,China
The effect of aging temperature on stress corrosion crocking of 17-4 precipitation-hardened(PH)stainless steel in simulated stimulant oil well environment was studied by the method B-NACE standard bent-beam test.It is found that when aging temperature ranges from 480 to 610℃,the sensitivity of hydrogen embrittlement decreases significantly.
Zhou Chengshuang,Zheng Shuqi,Chen Changfeng,Lu Guiwu China University of Petroleum,Beijing 102249,China
The compositions and structures of the passive films formed on 825 nickel base alloy lined pipe serving for one year in an actual corrosion environment including 2.0 MPa H2S and 1.5 MPa CO2 at a temperature of 55℃were investigated by X-ray photoelectron spectroscopy(XPS).The results show that the passive films formed on 825 nickel base alloy is not destroyed even thicker than air-formed one and the films are composed of multilayer with different composition in each layer:an external part composed of a mixture of Cr and Ni oxide(more Ni included)and an inner part composed of a mixture of Cr and Ni oxide(Cr-rich layer).
