The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipita...The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel. The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fee lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).展开更多
Thermal loss of exhaust flue gas accounts for the largest proportion of the total boiler thermal loss. Nowadays in China, the exhaust gas temperature in many thermal power plants is much higher than the designed value...Thermal loss of exhaust flue gas accounts for the largest proportion of the total boiler thermal loss. Nowadays in China, the exhaust gas temperature in many thermal power plants is much higher than the designed value, thus, the recycle and reuse of the waste heat of tail flue gas is necessary. However, lower exhaust gas temperature will aggravate low temperature corrosion of the tail heating surface, which also causes huge economic losses. In order to solve this problem, this paper designs a monitoring experiment platform of flue gas low temperature corrosion, which can measure the corrosion condition of different materials by different flue gas compositions and temperature corrosion speeds. Besides, effects of low temperature corrosion factors are analyzed to find the best exhaust gas temperature and the surface material of tail heating surface.展开更多
Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The exper...Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The experiments were carried out in 100A cell with low melting point electrolyte, the influences of cathodic current density, electrolytic temperature, density differences of bath and liquid aluminum on current efficiency (CE) were studied; when the electrolyte cryolite ratio was 2.5, w(BaC1_2) and w(NaCl) were 48% and 10%, respectively, CE reached 90% and specific energy consumption was 10.97k Wb/kg/kg. Because of the fact that aluminum metal obtained floated on the surface of molten electrolyte, this electrolysis method was then defined as low temperature aluminum floating electrolysis. The results showed that the new low temperature aluminum electrolysis process in the Na_3AlF_6-AlF_3-BaC1_2-NaCl bath system was practical and promising.展开更多
The influence of processing temperatures on the surface characteristics of AISI 204Cu austenitic stainless steel was investigated during a low temperature plasma nitrocarburizing.The resultant layer was a dual-layer s...The influence of processing temperatures on the surface characteristics of AISI 204Cu austenitic stainless steel was investigated during a low temperature plasma nitrocarburizing.The resultant layer was a dual-layer structure,which comprises a N-enriched layer on the top of C-enriched layer.The surface hardness and the layer thickness increase up to about HV 0.05 1000 and 20μm with increasing temperature.The specimen treated at 400°C shows a much enhanced corrosion resistance compared to the untreated steel.A loss in corrosion resistance was observed for specimens treated at temperatures above 430°C due to the formation of Cr2N.展开更多
The relationship between micro structure and corrosion behavior of high-grade pipeline steel under low-temperature conditions was comparatively investigated by the potentiodynamic polarization and electrochemical impe...The relationship between micro structure and corrosion behavior of high-grade pipeline steel under low-temperature conditions was comparatively investigated by the potentiodynamic polarization and electrochemical impedance spec-troscopy test combining with optical micrographs,scanning electron microscopy,transmission electron microscopy and electron back-scattered diffraction.The results showed that,compared with room and high temperature,low temperature could influence the corrosion behavior of high-grade pipeline steel,which means that the corrosion potential and current density decreased and the corrosion resistance increased significantly.Moreover,double layer structures of the interface became thicker and more compact.Under low-temperature environment,acicular ferrite had the martensite/austenite constituents with less amount and smaller size,a higher density of low angle grain boundaries and smaller effective grain sizes compared with granular bainite,which demonstrated higher corrosion resistance.展开更多
In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 mon...In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 month and 24 months differ significantly.The corrosion rate after 1 month during the summer season was 19.82 g/m^(2)·year and it decreased to 13.87 g/m^(2)·year after two years’exposure.Corrosion is initiated with pitting corrosion and then evolved to uniform corrosion with prolonging exposure time.The skyward surface exhibited a much severe corrosion than that of the groundward surface,attributed to the long-term existence of the adsorbed electrolyte layer.The corrosion products formed on the alloy exposed in Antarctica environment were MgCO_(3)·3H_(2)O,MgCO_(3)·5H_(2)O and Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O,with the MgCO_(3)·3H_(2)O as the dominant phase in the initial stage and the Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O as the dominant phase after long-term exposure.展开更多
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...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.展开更多
基金The DFG(Deutsche Forschungsgemeinschaf)is gratefully acknowledged for the financial support(DFG-BI 418/9-1).
文摘The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel. The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fee lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).
文摘Thermal loss of exhaust flue gas accounts for the largest proportion of the total boiler thermal loss. Nowadays in China, the exhaust gas temperature in many thermal power plants is much higher than the designed value, thus, the recycle and reuse of the waste heat of tail flue gas is necessary. However, lower exhaust gas temperature will aggravate low temperature corrosion of the tail heating surface, which also causes huge economic losses. In order to solve this problem, this paper designs a monitoring experiment platform of flue gas low temperature corrosion, which can measure the corrosion condition of different materials by different flue gas compositions and temperature corrosion speeds. Besides, effects of low temperature corrosion factors are analyzed to find the best exhaust gas temperature and the surface material of tail heating surface.
基金The project was financially supported by the National Natural Science Foundation of China! (Gmnt No.59574018)China Postdocto
文摘Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The experiments were carried out in 100A cell with low melting point electrolyte, the influences of cathodic current density, electrolytic temperature, density differences of bath and liquid aluminum on current efficiency (CE) were studied; when the electrolyte cryolite ratio was 2.5, w(BaC1_2) and w(NaCl) were 48% and 10%, respectively, CE reached 90% and specific energy consumption was 10.97k Wb/kg/kg. Because of the fact that aluminum metal obtained floated on the surface of molten electrolyte, this electrolysis method was then defined as low temperature aluminum floating electrolysis. The results showed that the new low temperature aluminum electrolysis process in the Na_3AlF_6-AlF_3-BaC1_2-NaCl bath system was practical and promising.
基金Project(2011AA192)supported by Dongeui University,Korea
文摘The influence of processing temperatures on the surface characteristics of AISI 204Cu austenitic stainless steel was investigated during a low temperature plasma nitrocarburizing.The resultant layer was a dual-layer structure,which comprises a N-enriched layer on the top of C-enriched layer.The surface hardness and the layer thickness increase up to about HV 0.05 1000 and 20μm with increasing temperature.The specimen treated at 400°C shows a much enhanced corrosion resistance compared to the untreated steel.A loss in corrosion resistance was observed for specimens treated at temperatures above 430°C due to the formation of Cr2N.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFB0304900)the National Natural Science Foundation of China(Grant No.51911530129).
文摘The relationship between micro structure and corrosion behavior of high-grade pipeline steel under low-temperature conditions was comparatively investigated by the potentiodynamic polarization and electrochemical impedance spec-troscopy test combining with optical micrographs,scanning electron microscopy,transmission electron microscopy and electron back-scattered diffraction.The results showed that,compared with room and high temperature,low temperature could influence the corrosion behavior of high-grade pipeline steel,which means that the corrosion potential and current density decreased and the corrosion resistance increased significantly.Moreover,double layer structures of the interface became thicker and more compact.Under low-temperature environment,acicular ferrite had the martensite/austenite constituents with less amount and smaller size,a higher density of low angle grain boundaries and smaller effective grain sizes compared with granular bainite,which demonstrated higher corrosion resistance.
基金The authors acknowledgement the Excellent Youth Science Fund of Shandong Province(No.ZR2022YQ44)the Fundamental Research Funds for the Central Universities(No.201762008).
文摘In this work,the outdoor corrosion behavior of AZ31B magnesium alloy in the Antarctic atmospheric environment was investigated.The surface corrosion state of the specimens exposed to the Antarctic atmosphere for 1 month and 24 months differ significantly.The corrosion rate after 1 month during the summer season was 19.82 g/m^(2)·year and it decreased to 13.87 g/m^(2)·year after two years’exposure.Corrosion is initiated with pitting corrosion and then evolved to uniform corrosion with prolonging exposure time.The skyward surface exhibited a much severe corrosion than that of the groundward surface,attributed to the long-term existence of the adsorbed electrolyte layer.The corrosion products formed on the alloy exposed in Antarctica environment were MgCO_(3)·3H_(2)O,MgCO_(3)·5H_(2)O and Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O,with the MgCO_(3)·3H_(2)O as the dominant phase in the initial stage and the Mg_(2)CO_(3)(OH)_(2)·0.5H_(2)O as the dominant phase after long-term exposure.
文摘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.
