The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning co...The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning confocal microscopy,scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy were used to reveal the related mechanism.The results showed that Cr_(2)O_(3) oxides together with a small number of spinel oxides were formed in sticking region since a small quantity of high-temperature water could pass through the gaps between the asperities to oxidize the materials.Widespread distribution of oxides in microslip region consisted of(Ni,Fe)Cr_(2)O_(4),because Ni^(2+)and Fe^(2+) ions could react with Cr_(2)O_(3) to generate a small amount of non-stoichiometric spinel oxides.The oxides around micropitting in microslip region consisted of double-layer structure.The outermost layer contained(Fe,Cr)-rich oxides due to the effect of fretting leading to mechanical mixing between Cr_(2)O_(3) and(Ni,Fe)(Fe,Cr)_(2)O_(4).The inner layer consisted of(Fe,Ni)-rich oxides owing to the consumption of Cr_(2)O_(3) by the reaction with Ni^(2+)and Fe^(2+) ions.The reciprocating motion of oxide particles in microslip region resulted in the stress-strain supporting the recrystallization for the formation and development of a tribologically transformed structure in subsurface and plowing effect by fretting in surface.展开更多
Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change o...Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer.The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport.Meanwhile,the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer,which is caused by the dissolution of Cr ions increased by increasing the DO concentration.Meanwhile,the chromium ion concentration increases with the dissolved oxygen concentration,which leads to a decrease in the thickness of the electric double layer,weakening the electrodynamic effect.The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees.This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.展开更多
基金financial supports of the Beijing Natural Science Foundation(Grant No.2194081)the Project funded by China Postdoctoral Science Foundation(Grant No.2018M641187)the Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-18-047A1)。
文摘The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning confocal microscopy,scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy were used to reveal the related mechanism.The results showed that Cr_(2)O_(3) oxides together with a small number of spinel oxides were formed in sticking region since a small quantity of high-temperature water could pass through the gaps between the asperities to oxidize the materials.Widespread distribution of oxides in microslip region consisted of(Ni,Fe)Cr_(2)O_(4),because Ni^(2+)and Fe^(2+) ions could react with Cr_(2)O_(3) to generate a small amount of non-stoichiometric spinel oxides.The oxides around micropitting in microslip region consisted of double-layer structure.The outermost layer contained(Fe,Cr)-rich oxides due to the effect of fretting leading to mechanical mixing between Cr_(2)O_(3) and(Ni,Fe)(Fe,Cr)_(2)O_(4).The inner layer consisted of(Fe,Ni)-rich oxides owing to the consumption of Cr_(2)O_(3) by the reaction with Ni^(2+)and Fe^(2+) ions.The reciprocating motion of oxide particles in microslip region resulted in the stress-strain supporting the recrystallization for the formation and development of a tribologically transformed structure in subsurface and plowing effect by fretting in surface.
基金financially supported by the National Natural Science Foundation of China(51901254,52001336)the Foundation Research Funds for the Central Universities(19lgpy22)the Shenzhen Science and Technology Program(2022A007)
文摘Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer.The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport.Meanwhile,the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer,which is caused by the dissolution of Cr ions increased by increasing the DO concentration.Meanwhile,the chromium ion concentration increases with the dissolved oxygen concentration,which leads to a decrease in the thickness of the electric double layer,weakening the electrodynamic effect.The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees.This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.
