The effect of Ca^2＋ on CO2 corrosion to X65 pipeline steel was investigated in the simulated stratum water of an oil field containing different concentrations of Ca^2＋. It is found that Ca^2＋ can enhance the corros...The effect of Ca^2＋ on CO2 corrosion to X65 pipeline steel was investigated in the simulated stratum water of an oil field containing different concentrations of Ca^2＋. It is found that Ca^2＋ can enhance the corrosion rate, especially in the Ca^2＋ concentration from 256 to 512 mg/L, which can be attributed to the growing grain size and loosing structure of corrosion scales with increasing Ca^2＋ concentration. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） investigations reveal that a complex carbonate （Fe, Ca）CO3 forms at high Ca^2＋ concentration due to the gradual replacement of Fe^2＋ in FeCO3 by Ca^2＋.展开更多
With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started ...With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate systems.Studies also present different opinions on whether coatings can improve or reduce the fatigue life of substrates.In this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.展开更多
The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results sh...The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.展开更多
The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of ...The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of Cr,a thorough study dealing with the passivation behaviors of this metal,including the structure and composition of the passive film as well as related reaction mechanisms,is required.Here,continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods.Different models with various surface conditions are applied.Passivation is found to begin in the active region,and a fully coated surface mainly with oxide is likely to be the starting point of the passive region.The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.展开更多
Carbon atoms segregate in the surface region for polished AISI 440C stainless steel After ion implanta tion, the surface carbon atoms exist in different forms. To elucidate their existence, surface structures and carb...Carbon atoms segregate in the surface region for polished AISI 440C stainless steel After ion implanta tion, the surface carbon atoms exist in different forms. To elucidate their existence, surface structures and carbon chemical states o[ unimplanted, N~ implanted, Ti＋ implanted and N＋/Ti＋ co-implanted samples were analyzed by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and X-ray photoelectron spectroscopy （XPS）. The results indicated that various phases form in the surface or subsurface region after ion implantation, while the surface topography of the samples remains intact. For polished unimplanted sample, besides some Fe3 C phase and C- C phase, Cr, Cs phase dominates its surface region. Little change of carbon chemical states occurs after N＋ ion im- plantation. For Ti＋ implanted sample, besides some metal oxycarbide phases, most carbon amorphous phases form in surface region. Concerning N＋/Ti＋ co-implantation, CrrCs compound as well as Fe^C phase dominates the sur face region while no C-C phase is found. In addition, compared with single ion implantation, N＋/Ti＋ co-implanta tion would increase the ion implantation depth significantly. The formed phases of the carbon atoms play an impor- tant role in affecting the surface properties of AISI 440C stainless steel.展开更多
基金supported by the National Natural Science Foundation of China (No.50571012)
文摘The effect of Ca^2＋ on CO2 corrosion to X65 pipeline steel was investigated in the simulated stratum water of an oil field containing different concentrations of Ca^2＋. It is found that Ca^2＋ can enhance the corrosion rate, especially in the Ca^2＋ concentration from 256 to 512 mg/L, which can be attributed to the growing grain size and loosing structure of corrosion scales with increasing Ca^2＋ concentration. X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） investigations reveal that a complex carbonate （Fe, Ca）CO3 forms at high Ca^2＋ concentration due to the gradual replacement of Fe^2＋ in FeCO3 by Ca^2＋.
基金financially supported by the National Natural Science Foundation of China (Nos.51922002 and 51771025)the Fundamental Research Funds for the Central Universities (No.FRF-TP-17-19-003C1Z)。
文摘With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate systems.Studies also present different opinions on whether coatings can improve or reduce the fatigue life of substrates.In this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.
文摘The effect of hydrogen on the fractttre behaviors of Incoloy alloy 825 was investigated by means of slow strain rate testing （SSRT） Hydrogen was introduced into the sample by electrochemical charging. The results show that surface microcracks form gradually during ag- ing at room temperature when desorption of hydrogen takes place after hydrogen charging at a current density of 5 mA/cm^2 for 24 h. SSRT shows that the increase of ductility loss is significantly obvious as the hydrogen charging current density increases. Scanning electron microscopy （SEM） images reveal ductile fracture in the pre-charged sample with low current densities, while the fracture includes small quasi-cleavage regions and tends to be brittle fracture as the hydrogen charging current density increases to 5 mA/cm^2.
基金financially supported by the National Key Research and Development Program of China(No.2017YFB0702100)the National Natural Science Foundation of China(Nos.51571028,51431004,and U1706221)financial support from China Scholarship Council
文摘The well-known anti-corrosive property of stainless steels is largely attributed to the addition of Cr,which can assist in forming an inert film on the corroding surface.To maximize the corrosion-resistant ability of Cr,a thorough study dealing with the passivation behaviors of this metal,including the structure and composition of the passive film as well as related reaction mechanisms,is required.Here,continuous electrochemical adsorptions of OH-groups of water molecules onto Cr terraces in acid solutions are investigated using DFT methods.Different models with various surface conditions are applied.Passivation is found to begin in the active region,and a fully coated surface mainly with oxide is likely to be the starting point of the passive region.The calculated limiting potentials are in reasonable agreement with passivation potentials observed via experiment.
基金Sponsored by National Natural Science Foundation of China(51075004)Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality(PHR201107109)Importation and Development of High-caliber Talents Project of Beijing Municipal Institutions(CIT&TCD201304005)
文摘Carbon atoms segregate in the surface region for polished AISI 440C stainless steel After ion implanta tion, the surface carbon atoms exist in different forms. To elucidate their existence, surface structures and carbon chemical states o[ unimplanted, N~ implanted, Ti＋ implanted and N＋/Ti＋ co-implanted samples were analyzed by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and X-ray photoelectron spectroscopy （XPS）. The results indicated that various phases form in the surface or subsurface region after ion implantation, while the surface topography of the samples remains intact. For polished unimplanted sample, besides some Fe3 C phase and C- C phase, Cr, Cs phase dominates its surface region. Little change of carbon chemical states occurs after N＋ ion im- plantation. For Ti＋ implanted sample, besides some metal oxycarbide phases, most carbon amorphous phases form in surface region. Concerning N＋/Ti＋ co-implantation, CrrCs compound as well as Fe^C phase dominates the sur face region while no C-C phase is found. In addition, compared with single ion implantation, N＋/Ti＋ co-implanta tion would increase the ion implantation depth significantly. The formed phases of the carbon atoms play an impor- tant role in affecting the surface properties of AISI 440C stainless steel.
