Some furnace tubes made of the austenitic stainless steel 1Cr18Ni9Ti for heating crude oil ex- hibited leakage and were on fire in a refinery.Cor- rosion failure analysis was conducted to explore the cause of failure....Some furnace tubes made of the austenitic stainless steel 1Cr18Ni9Ti for heating crude oil ex- hibited leakage and were on fire in a refinery.Cor- rosion failure analysis was conducted to explore the cause of failure.Macro-and microexamination in- dicated the failure to be stress corrosion cracking by chloride and sulphide with cracks initiating on the inner surface in weld or heat affected zone.Veri- fying tests demonstrated that the cracks occurred during operating period.The cause of failure was related to the critical situation of the refinery:lack of desalination equipment,lots of steam with liquid film on inside tube walls owing to mixing crude oil with a great amount of water,increasing decompo- sition of inorganic salts and lowering the tempera- ture in furnace tubes.展开更多
Silicon was added to the surface of 304 stain- less steel by laser melting the sprayed preplaced Si powders.The optical microscopy,X-ray diffraction and EPMA were employed to investigate the microstructure and chemica...Silicon was added to the surface of 304 stain- less steel by laser melting the sprayed preplaced Si powders.The optical microscopy,X-ray diffraction and EPMA were employed to investigate the microstructure and chemical composition of the laser surface alloyed layer.The hardness of the al- loyed layer was measured by microhardness test and wear resistance was evaluated by scratch test. Corrosion resistance of laser alloyed sample was studied in 1N H_2SO_4+0.1N NaCl and 0.5N HCl+0.5N NaCl aqueous solutions.A microcrystalline intermetallic compound coating with smooth surface and good chemical homogeneity without porosity and crack is ob- tained.The hardness is about 720 HV.The wear re- sistance is 2 times better than that of the substrate. The corrosion resistance of the laser alloyed sample is much better than that of 304 stainless steel sample.展开更多
A new-type of β-NiAl coating containing Y_2O_3 particles was obtained by electrolytic co-deposition and pack aluminizing techniques,and the influences of the nature of Y_2O_3 and its content on the oxidation behaviou...A new-type of β-NiAl coating containing Y_2O_3 particles was obtained by electrolytic co-deposition and pack aluminizing techniques,and the influences of the nature of Y_2O_3 and its content on the oxidation behaviour of the coating at 1100℃ were studied.The test results indicate that the oxidation rates of the composite coatings are reduced and the scale adhesion is also improved remarkably.The content of Y_2O_3 has little influence on the oxidation rates of the composite coatings,but does obviously on the scale adhesion by modifying the configura- tion of the oxides at the scale-coating interface.The needle-like oxides penetrating into the coating show an obvious keying effect.A part of the dispersed Y_2O_3 in the as-deposited coating accumulates and forms a Y_2O_3-rich layer at the coating-substrate interface immediately after aluminizing.The layer is beneficial to reduce the degradation of the composite coating.展开更多
By means of EPMA,SIMS and XTEM tech- niques,the element distribution at the transition zone of Y-modified ion plated titanium and titanium nitride film on A3 steel substrate and the variation of the element content on...By means of EPMA,SIMS and XTEM tech- niques,the element distribution at the transition zone of Y-modified ion plated titanium and titanium nitride film on A3 steel substrate and the variation of the element content on the surface of the evaporation source before and after service were studied in detail.A mode was proposed in terms of preferential evaporation and micro-tunnel trans- portation of Y at the interface of film/substrate.展开更多
The cyclic oxidation resistance of cast Ni-base superalloy K38G and its sputtered micro-grained film were studied between 950℃ and room temper- ature in air.The results show that the weight gain of micrograined films...The cyclic oxidation resistance of cast Ni-base superalloy K38G and its sputtered micro-grained film were studied between 950℃ and room temper- ature in air.The results show that the weight gain of micrograined films is much less than that of cast al- loy during cyclic oxidation,and the resistance of micro-grained fihns is even better than that of the aluminide coating on the same alloy.On the surface of cast alloy K38G,complex oxide scales of Cr_2O_3, TiO_2 and NiCr_2O_4 spinel formed and they began to spall alter about 30 cycles of test.However,on the micro-grained films,continuous and thin α-Al_2O_2 scale was formed and did not spall throughout the cyclic oxidation test.展开更多
Electrochemical impedance techniques have been widely used in evaluating organic coatings in aqueous solution. Recently, the study on molten salts induced corrosion by electrochemical impedance has also received incre...Electrochemical impedance techniques have been widely used in evaluating organic coatings in aqueous solution. Recently, the study on molten salts induced corrosion by electrochemical impedance has also received increasing attention. It is expected to use impedance techniques to monitor high temperature salts corrosion in fully operational combustion equipment, such as power generation boilers, refinery equipment, fluidized bed combustion systems and other installations. But there展开更多
文摘Some furnace tubes made of the austenitic stainless steel 1Cr18Ni9Ti for heating crude oil ex- hibited leakage and were on fire in a refinery.Cor- rosion failure analysis was conducted to explore the cause of failure.Macro-and microexamination in- dicated the failure to be stress corrosion cracking by chloride and sulphide with cracks initiating on the inner surface in weld or heat affected zone.Veri- fying tests demonstrated that the cracks occurred during operating period.The cause of failure was related to the critical situation of the refinery:lack of desalination equipment,lots of steam with liquid film on inside tube walls owing to mixing crude oil with a great amount of water,increasing decompo- sition of inorganic salts and lowering the tempera- ture in furnace tubes.
文摘Silicon was added to the surface of 304 stain- less steel by laser melting the sprayed preplaced Si powders.The optical microscopy,X-ray diffraction and EPMA were employed to investigate the microstructure and chemical composition of the laser surface alloyed layer.The hardness of the al- loyed layer was measured by microhardness test and wear resistance was evaluated by scratch test. Corrosion resistance of laser alloyed sample was studied in 1N H_2SO_4+0.1N NaCl and 0.5N HCl+0.5N NaCl aqueous solutions.A microcrystalline intermetallic compound coating with smooth surface and good chemical homogeneity without porosity and crack is ob- tained.The hardness is about 720 HV.The wear re- sistance is 2 times better than that of the substrate. The corrosion resistance of the laser alloyed sample is much better than that of 304 stainless steel sample.
基金The project supported by the National Natural Foundation of China
文摘A new-type of β-NiAl coating containing Y_2O_3 particles was obtained by electrolytic co-deposition and pack aluminizing techniques,and the influences of the nature of Y_2O_3 and its content on the oxidation behaviour of the coating at 1100℃ were studied.The test results indicate that the oxidation rates of the composite coatings are reduced and the scale adhesion is also improved remarkably.The content of Y_2O_3 has little influence on the oxidation rates of the composite coatings,but does obviously on the scale adhesion by modifying the configura- tion of the oxides at the scale-coating interface.The needle-like oxides penetrating into the coating show an obvious keying effect.A part of the dispersed Y_2O_3 in the as-deposited coating accumulates and forms a Y_2O_3-rich layer at the coating-substrate interface immediately after aluminizing.The layer is beneficial to reduce the degradation of the composite coating.
文摘By means of EPMA,SIMS and XTEM tech- niques,the element distribution at the transition zone of Y-modified ion plated titanium and titanium nitride film on A3 steel substrate and the variation of the element content on the surface of the evaporation source before and after service were studied in detail.A mode was proposed in terms of preferential evaporation and micro-tunnel trans- portation of Y at the interface of film/substrate.
基金This work was supported by the National Nat- ural Science Foundation of China
文摘The cyclic oxidation resistance of cast Ni-base superalloy K38G and its sputtered micro-grained film were studied between 950℃ and room temper- ature in air.The results show that the weight gain of micrograined films is much less than that of cast al- loy during cyclic oxidation,and the resistance of micro-grained fihns is even better than that of the aluminide coating on the same alloy.On the surface of cast alloy K38G,complex oxide scales of Cr_2O_3, TiO_2 and NiCr_2O_4 spinel formed and they began to spall alter about 30 cycles of test.However,on the micro-grained films,continuous and thin α-Al_2O_2 scale was formed and did not spall throughout the cyclic oxidation test.
基金Project supported by the National Natural Science Foundation of China.
文摘Electrochemical impedance techniques have been widely used in evaluating organic coatings in aqueous solution. Recently, the study on molten salts induced corrosion by electrochemical impedance has also received increasing attention. It is expected to use impedance techniques to monitor high temperature salts corrosion in fully operational combustion equipment, such as power generation boilers, refinery equipment, fluidized bed combustion systems and other installations. But there
