It was found that the steel plate in the composite plate in the WJ-8 fastener used in high speed rail is rusty. The objective of this study is to test the zinc coating of the steel plate. A literature review was condu...It was found that the steel plate in the composite plate in the WJ-8 fastener used in high speed rail is rusty. The objective of this study is to test the zinc coating of the steel plate. A literature review was conducted to identify the zinc coating techniques, and the companies that can provide different coating service was identified. A salt fog chamber was built that was in compliance with the ANSI B117 code, and the steel plates that were coated by the identified companies were tested using the salt fog chamber. The results indicated that the coating technique that had the best performance in preventing corrosion was the Greenkote plates with passivation. The galvanized option had the roughest coating layer, and it was the most reactive in the salt water solution. This makes it non-ideal for the dynamic rail environment because the increased friction of the plate could damage the supports, especially during extreme temperatures that would cause the rail to expand or contract. Greenkote with Phosphate and ArmorGalv also provided increased corrosion prevention with a smooth, strong finish, but it had more rust on the surface area than the Greenkote with ELU passivation. The ArmorGalv sample had more rust on the surface area than the Greenkote samples. This may not be a weakness in the ArmorGalv process;rather, it likely was the result of this particular sample not having the added protection of a colored coating.展开更多
LaMgAl11O19thermal barrier coatings(TBCs) were applied to carbon steels with a NiCoCrAlY bond coat by plasma spraying. The effects of heat treatment on the corrosion resistance of carbon steel coated with LaMgAl11O1...LaMgAl11O19thermal barrier coatings(TBCs) were applied to carbon steels with a NiCoCrAlY bond coat by plasma spraying. The effects of heat treatment on the corrosion resistance of carbon steel coated with LaMgAl11O19TBCs were investigated in 3.5wt% Na Cl solution using polarization curves, electrochemical impedance spectroscopy(EIS), scanning electron microscopy(SEM), and X-ray diffraction(XRD). The results show that a large number of cracks are found in the LaMgAl11O19TBCs after the samples are heat-treated, including some through-thickness cracks. The corrosion forms of the as-sprayed and heat-treated TBCs are uniform corrosion and pitting corrosion, respectively. The as-sprayed TBCs exhibit three EIS time constants after being immersed for less than 7 d, and then a new time constant appears because of steel substrate corrosion. When the immersion time is increased to 56 d, a Warburg impedance(W) component appears in the EIS data. The EIS data for the heat-treated TBCs exhibit only two time constants after the samples are immersed for less than 14 d, and a new time constant appears when the immersion time is increased further. The heat treatment reduces the corrosion resistance of carbon steel coated with LaMgAl11O19TBCs. The corrosion products are primarily γ-Fe OOH and Fe3O4.展开更多
The industrial application of an exterior three-layer anticorrosive polypropylene coating system(3PP)on large-diameter(larger than Φ600 mm)steel pipes was developed using an experimental process simulation study and ...The industrial application of an exterior three-layer anticorrosive polypropylene coating system(3PP)on large-diameter(larger than Φ600 mm)steel pipes was developed using an experimental process simulation study and the optimization of raw materials inspection,steel pipe surface pretreatments,and water cooling control on a coating application process.The coating properties meet ISO standard 21809 on buried or submerged 3PP pipelines used in the petroleum and natural gas industries.Differential scanning calorimetry and X-ray diffraction were used to analyze the crystallinities and grain sizes of polypropylene(PP)top coats with different cooling rates.Increasing the melt cooling rate reduces the crystallinity and grain size of the PP top coat and enhances its strength and toughness.展开更多
Reduced activation ferritic/martensitic steel (RAFM) is recognized as the primary candidate structural material for ITER's test blanket module (TBM). To provide a material and property database for the design and...Reduced activation ferritic/martensitic steel (RAFM) is recognized as the primary candidate structural material for ITER's test blanket module (TBM). To provide a material and property database for the design and fabrication of the Chinese helium cooled ceramic breeding TBM (CN HCCB TBM), a type of RAFM steel named CLF-1 was developed and chaxacter^zed at the Southwestern Institute of Physics (SWIP), China. In this paper, the R&D status of CLF-1 steel and the technical issues in using CLF-1 steel to manufacture CN HCCB TBM were reviewed, including the steel manufacture and different welding technologies. Several kinds of property data have been obtained for its application to the design of the ITER TBM.展开更多
In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in wa...In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.展开更多
In recent years,the concern about environmental protection is increasing on a world scale.Major manufacturers of home appliances and OA equipment have introduced so-called 'green procurement schemes' for reduc...In recent years,the concern about environmental protection is increasing on a world scale.Major manufacturers of home appliances and OA equipment have introduced so-called 'green procurement schemes' for reducing environmentally harmful substances in manufacturing process and end products. Under such background,a new type of chromate-free organic composite coated electro-galvanized steel sheet with high conductivity was developed by Baosteel,which meets the EU RoHS Directive(Restriction of the Hazardous Substances) and other related laws and regulations on environmental safety.It also provides excellent surface electrical conductivity,corrosion resistance,fingerprint resistance,solvent resistance,coating adhesion, heat resistance,formability and other special properties to meet the demand of manufacture's process of OA machine. Compared with previously developed anti-fingerprinting coated electro-galvanized steel sheet,this newly developed product has a good balance between high corrosion resistance(time to 5%white rust in salt spray test is 120 h for flat panel and 72 h for worked potion) and conductivity(surface electro-resistivity in accordance with LOREAST is less than 0.1 milliohm ) due to the special design of coating's structure.Besides,It also provides the properties of grounding and shielding against electromagnetic waves.The evaluation of surface performances of new product showed that it is comparable or even better than the similar products. Currently,the newly developed product has been commercialized. In this paper,the major properties are discussed,such as corrosion resistance,surface electrical conductivity, fingerprint resistance,solvent resistance,coating adhesion(ink/melamine alkyd paint),heat resistance and formability.Furthermore,the application is also briefly described.展开更多
The fabrication of an alumina-metal composite coating onto a carbon steel substrate by using a self-propagating high-temperature synthesis technique was demonstrated. The effects of the type and thickness of the pre-c...The fabrication of an alumina-metal composite coating onto a carbon steel substrate by using a self-propagating high-temperature synthesis technique was demonstrated. The effects of the type and thickness of the pre-coated layer on the binding structure and surface qual- ity of the coating were systematically investigated. The macrostructure, phase composition, and bonding interface between the coating and the substrate were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS). The diffraction patterns indicated that the coating essentially consisted of α-Al2O3, Fe(Cr), and FeO-Al2O3. With an increase in the thickness of the pre-coated working layer, the coating became more smooth and compact. The transition layer played an important role in enhancing the binding between the coating and the substmte. When the pre-coated working layer was 10 mm and the pre-coated transition layer was 1 ram, a compact structure and metallurgical bonding with the substrate were obtained. Thermal shock test results indicated that the ceramic coating exhibited good thermal shock resistance when the sample was rapidly quenched from 800℃ to room temperature by plunging into water.展开更多
To improve the corrosion resistance of phosphate coatings, the phosphated hot-dip galvanized (HDG) steel was post-sealed with cerium nitrate solution. The morphology, composition, corrosion resistance of the coatings ...To improve the corrosion resistance of phosphate coatings, the phosphated hot-dip galvanized (HDG) steel was post-sealed with cerium nitrate solution. The morphology, composition, corrosion resistance of the coatings was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and neutral salt spray (NSS) tests. The results show that after post-sealing the phosphated HDG samples with cerium nitrate solution, the pores among the zinc phosphate crystals are sealed by the compounds containing phosphorus, oxygen and cerium; the zinc phosphate crystals are covered by the flocculent cerium compounds; and the continuous composite coatings are formed on HDG steel. The corrosion resistance of the composite coatings, which increases with the increase in phosphating time and cerium nitrate post-sealing time, is far higher than that of the single phosphate coatings. The composite coatings with the optimal corrosion resistance are obtained for phosphating 300 s and post-sealing 300 s; and the corrosion resistance is more outstanding than that of the chromate coatings.展开更多
A series of rare earth (RE) dispersed chromizing coatings were produced on P 110 steel by pack cementation. The orthogonal array design (OAD)was applied to set the experiments. An artificial neural network (ANN)...A series of rare earth (RE) dispersed chromizing coatings were produced on P 110 steel by pack cementation. The orthogonal array design (OAD)was applied to set the experiments. An artificial neural network (ANN) approach is employed to predict the thickness values of the obtained chromizing coatings based on the OAD tests results. The results revealed that the built model was reliable, the thickness values of chromizing coatings were well predicted at selected process parameters, and the predicted error lied in rational range.展开更多
Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as b...Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as billet temperature,temperature distribution after reheating,argon gas pressure,transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12.The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear,thus being useful for further tool design.Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.展开更多
The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-e...The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.展开更多
Two low alloy steels 0.5Cr-0.5Mo-0.25V and H85 were pack-aluminized at 900°for 4 h by using Fe-Al powder mixture containing 48% Fe, 20.6% Al- 29.4% Al2O3 and 2% NH4Cl by weight. The microhardness and oxidation re...Two low alloy steels 0.5Cr-0.5Mo-0.25V and H85 were pack-aluminized at 900°for 4 h by using Fe-Al powder mixture containing 48% Fe, 20.6% Al- 29.4% Al2O3 and 2% NH4Cl by weight. The microhardness and oxidation resistance at 900℃ of the aluminide coatings were studied. It was found that pack-aluminizing improves the microhardness of the 0.5Cro.5Mo-0.25V steel while it reduces the microhardness of the H85 steel. Pack aluminizing highly improves the oxidation resistance after 20h exposure at 900℃ in air for the investigated steels.展开更多
Silicone coatings have been used in this study. The method adopted was the liquid drop analysis on the coated fabrics. The contact angle between a liquid drop and the fabric surface was measured with two liquids conti...Silicone coatings have been used in this study. The method adopted was the liquid drop analysis on the coated fabrics. The contact angle between a liquid drop and the fabric surface was measured with two liquids continuously and recorded by a computer. The surface energy was calculated by means of Owens method.Kinetic measurement was adopted. The contact angle of liquids on the fabric coated silicone decreased with time was found. A compound solution DX has been found, so that the contact angle of the liquids on the fabric washed with DX becomes constant, and the surface energy of the fabric can be reduced to below 15 mJ/m2.展开更多
Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction (XRD) tests were carried out. The study discovers that the deficit of alloying was higher...Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction (XRD) tests were carried out. The study discovers that the deficit of alloying was higher on both sides of the steel sheet when compared to the center and the thickness of the coating on the sides was also higher than the center. The results of the XRD tests demonstrate that the microstructure of the coating with a lack of alloy is mainly composed of zinc,ζ and δ. They also indicate that the lack of alloying is mainly due to a lower galvannealing temperature and thicker coating. It is shown by the optical micrographs of coating that the δ phase forms first in a discontinuous manner at the interface and then rapidly pushes towards the coating and enlarges.展开更多
Zn-Mg alloy coatings were obtained by physical vapor deposition (PVD) on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction ...Zn-Mg alloy coatings were obtained by physical vapor deposition (PVD) on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction (XRD) ,scanning electron microscope (SEM) and glow discharge optical emission spectrometry (GDOES). It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.展开更多
Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating. The effects of surface roughness on the surface lubrication perform...Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating. The effects of surface roughness on the surface lubrication performance of the steel sheets were examined using a friction coefficient tester. Results revealed large dynamic friction coefficients for the galvanized steel sheets, which increased remarkably with surface roughness. Once the self-lubricated coating was applied, significant drops in the dynamic friction coefficients were measured. After the first stage of the friction test,the coefficients were almost unchanged, which reflected a weak dependence on the surface roughness of the self-lubricated steel sheets. However, the dynamic friction coefficients gradually increased as the test progressed, where these increase clearly correlated with the surface roughness of the self-lubricated steel sheets.展开更多
Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer....Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.展开更多
This paper presents the results of experimental work carried out in dry turning of cast duplex stainless steels (ASTM A 995 Grade4A and ASTM A 995 Grade5A) using TiC and TiCN coated cemented carbide cutting tools. The...This paper presents the results of experimental work carried out in dry turning of cast duplex stainless steels (ASTM A 995 Grade4A and ASTM A 995 Grade5A) using TiC and TiCN coated cemented carbide cutting tools. The turning tests were conducted at five different cutting speeds (80, 100, 120, 140 and 160 m/min) and three different feed rates (0.04, 0.08 and 0.12 mm/rev) with a constant depth of cut (0.5 mm). The influence of cutting speed and feed rate on the machined surface roughness was investigated. Texture analysis (Bulk) was also carried out to study the impact of preferred orientation on the resulting surface roughness. The result reveals that the increasing cutting speed decreases the surface roughness till a particular point and then increases whereas;the surface roughness value decreases with the decreasing feed rate. Presence of alpha fiber (Bulk texture analysis) in the austenite phase of 4A work piece material leads to better surface finish. Among both the grades, surface finish of grade 4A is better than grade 5A work piece material.展开更多
Al coated steel sheets with excellent heat resistance,thermal reflection,and corrosion resistance are widely used in various applications.The laser weldability of the Al coated steel sheet for full penetration welding...Al coated steel sheets with excellent heat resistance,thermal reflection,and corrosion resistance are widely used in various applications.The laser weldability of the Al coated steel sheet for full penetration welding was reported.The phenomenon caused by intermixed aluminum and behavior of aluminum in the weld were investigated.Al coated steel sheets that have various thickness and coating mass were prepared for laser welding.The effects of parameters such as welding conditions and Al coating conditions were investigated.Al content mixed in the weld after laser welding was evaluated,and then a correlation between the mixed Al and mechanical properties was investigated.The results show that the Al-rich zones which have Fe-Al intermetallic compounds are found in the weld.The intermetallic compounds cause the decreased strength of the weld.展开更多
The flow characteristics of aluminum coated boron steel in hot press forming were investigated.Furthermore,the effects of aluminum coated layer on press forming were analyzed during deep drawing.The results show that ...The flow characteristics of aluminum coated boron steel in hot press forming were investigated.Furthermore,the effects of aluminum coated layer on press forming were analyzed during deep drawing.The results show that aluminum coated boron steel exhibits a high sensitivity on temperature and strain rate.Aluminum coating layer appears in surface flaking in a temperature range of 700-800 ℃,but smooth surface is formed above 900 ℃.展开更多
文摘It was found that the steel plate in the composite plate in the WJ-8 fastener used in high speed rail is rusty. The objective of this study is to test the zinc coating of the steel plate. A literature review was conducted to identify the zinc coating techniques, and the companies that can provide different coating service was identified. A salt fog chamber was built that was in compliance with the ANSI B117 code, and the steel plates that were coated by the identified companies were tested using the salt fog chamber. The results indicated that the coating technique that had the best performance in preventing corrosion was the Greenkote plates with passivation. The galvanized option had the roughest coating layer, and it was the most reactive in the salt water solution. This makes it non-ideal for the dynamic rail environment because the increased friction of the plate could damage the supports, especially during extreme temperatures that would cause the rail to expand or contract. Greenkote with Phosphate and ArmorGalv also provided increased corrosion prevention with a smooth, strong finish, but it had more rust on the surface area than the Greenkote with ELU passivation. The ArmorGalv sample had more rust on the surface area than the Greenkote samples. This may not be a weakness in the ArmorGalv process;rather, it likely was the result of this particular sample not having the added protection of a colored coating.
基金financially supported by the Fundamental Research Funds for the Central Universities of China(No.FRF-AS-11-015B)the Science Research Program of Beijing Municipal Commission of Education(No.00012087)
文摘LaMgAl11O19thermal barrier coatings(TBCs) were applied to carbon steels with a NiCoCrAlY bond coat by plasma spraying. The effects of heat treatment on the corrosion resistance of carbon steel coated with LaMgAl11O19TBCs were investigated in 3.5wt% Na Cl solution using polarization curves, electrochemical impedance spectroscopy(EIS), scanning electron microscopy(SEM), and X-ray diffraction(XRD). The results show that a large number of cracks are found in the LaMgAl11O19TBCs after the samples are heat-treated, including some through-thickness cracks. The corrosion forms of the as-sprayed and heat-treated TBCs are uniform corrosion and pitting corrosion, respectively. The as-sprayed TBCs exhibit three EIS time constants after being immersed for less than 7 d, and then a new time constant appears because of steel substrate corrosion. When the immersion time is increased to 56 d, a Warburg impedance(W) component appears in the EIS data. The EIS data for the heat-treated TBCs exhibit only two time constants after the samples are immersed for less than 14 d, and a new time constant appears when the immersion time is increased further. The heat treatment reduces the corrosion resistance of carbon steel coated with LaMgAl11O19TBCs. The corrosion products are primarily γ-Fe OOH and Fe3O4.
文摘The industrial application of an exterior three-layer anticorrosive polypropylene coating system(3PP)on large-diameter(larger than Φ600 mm)steel pipes was developed using an experimental process simulation study and the optimization of raw materials inspection,steel pipe surface pretreatments,and water cooling control on a coating application process.The coating properties meet ISO standard 21809 on buried or submerged 3PP pipelines used in the petroleum and natural gas industries.Differential scanning calorimetry and X-ray diffraction were used to analyze the crystallinities and grain sizes of polypropylene(PP)top coats with different cooling rates.Increasing the melt cooling rate reduces the crystallinity and grain size of the PP top coat and enhances its strength and toughness.
基金supported by the China Nuclear Energy Development Program (No. H6603100)
文摘Reduced activation ferritic/martensitic steel (RAFM) is recognized as the primary candidate structural material for ITER's test blanket module (TBM). To provide a material and property database for the design and fabrication of the Chinese helium cooled ceramic breeding TBM (CN HCCB TBM), a type of RAFM steel named CLF-1 was developed and chaxacter^zed at the Southwestern Institute of Physics (SWIP), China. In this paper, the R&D status of CLF-1 steel and the technical issues in using CLF-1 steel to manufacture CN HCCB TBM were reviewed, including the steel manufacture and different welding technologies. Several kinds of property data have been obtained for its application to the design of the ITER TBM.
文摘In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.
文摘In recent years,the concern about environmental protection is increasing on a world scale.Major manufacturers of home appliances and OA equipment have introduced so-called 'green procurement schemes' for reducing environmentally harmful substances in manufacturing process and end products. Under such background,a new type of chromate-free organic composite coated electro-galvanized steel sheet with high conductivity was developed by Baosteel,which meets the EU RoHS Directive(Restriction of the Hazardous Substances) and other related laws and regulations on environmental safety.It also provides excellent surface electrical conductivity,corrosion resistance,fingerprint resistance,solvent resistance,coating adhesion, heat resistance,formability and other special properties to meet the demand of manufacture's process of OA machine. Compared with previously developed anti-fingerprinting coated electro-galvanized steel sheet,this newly developed product has a good balance between high corrosion resistance(time to 5%white rust in salt spray test is 120 h for flat panel and 72 h for worked potion) and conductivity(surface electro-resistivity in accordance with LOREAST is less than 0.1 milliohm ) due to the special design of coating's structure.Besides,It also provides the properties of grounding and shielding against electromagnetic waves.The evaluation of surface performances of new product showed that it is comparable or even better than the similar products. Currently,the newly developed product has been commercialized. In this paper,the major properties are discussed,such as corrosion resistance,surface electrical conductivity, fingerprint resistance,solvent resistance,coating adhesion(ink/melamine alkyd paint),heat resistance and formability.Furthermore,the application is also briefly described.
基金financially supported by the Ministry of Education of China (No. 625010312)the Research and Innovation Project for College Graduates of Jiangsu Province, China (No. CXZZ13_0245)
文摘The fabrication of an alumina-metal composite coating onto a carbon steel substrate by using a self-propagating high-temperature synthesis technique was demonstrated. The effects of the type and thickness of the pre-coated layer on the binding structure and surface qual- ity of the coating were systematically investigated. The macrostructure, phase composition, and bonding interface between the coating and the substrate were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS). The diffraction patterns indicated that the coating essentially consisted of α-Al2O3, Fe(Cr), and FeO-Al2O3. With an increase in the thickness of the pre-coated working layer, the coating became more smooth and compact. The transition layer played an important role in enhancing the binding between the coating and the substmte. When the pre-coated working layer was 10 mm and the pre-coated transition layer was 1 ram, a compact structure and metallurgical bonding with the substrate were obtained. Thermal shock test results indicated that the ceramic coating exhibited good thermal shock resistance when the sample was rapidly quenched from 800℃ to room temperature by plunging into water.
文摘To improve the corrosion resistance of phosphate coatings, the phosphated hot-dip galvanized (HDG) steel was post-sealed with cerium nitrate solution. The morphology, composition, corrosion resistance of the coatings was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and neutral salt spray (NSS) tests. The results show that after post-sealing the phosphated HDG samples with cerium nitrate solution, the pores among the zinc phosphate crystals are sealed by the compounds containing phosphorus, oxygen and cerium; the zinc phosphate crystals are covered by the flocculent cerium compounds; and the continuous composite coatings are formed on HDG steel. The corrosion resistance of the composite coatings, which increases with the increase in phosphating time and cerium nitrate post-sealing time, is far higher than that of the single phosphate coatings. The composite coatings with the optimal corrosion resistance are obtained for phosphating 300 s and post-sealing 300 s; and the corrosion resistance is more outstanding than that of the chromate coatings.
基金Funded by the National Natural Science Foundation of China(No.51171125)the China Postdoctoral Science Foundation (No.2012M520604)+1 种基金the Youth Foundation of Taiyuan University of Technology (No.2012L050)the Foundation for Talents Introduction of Taiyuan University of Technology
文摘A series of rare earth (RE) dispersed chromizing coatings were produced on P 110 steel by pack cementation. The orthogonal array design (OAD)was applied to set the experiments. An artificial neural network (ANN) approach is employed to predict the thickness values of the obtained chromizing coatings based on the OAD tests results. The results revealed that the built model was reliable, the thickness values of chromizing coatings were well predicted at selected process parameters, and the predicted error lied in rational range.
基金the German Research Foundation for the financial support within the project T01 of the TFB 289 ‘Forming of metals in the semi-solid state and their properties’
文摘Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as billet temperature,temperature distribution after reheating,argon gas pressure,transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12.The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear,thus being useful for further tool design.Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.
文摘The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life.However,due to the cyclic thermal load caused by high-temperature gunpowder,micro-element damage tends to occur within the Cr coating/steel substrate interface,leading to a gradual deterioration in macro-mechanical properties for the material in the related region.In order to mimic this cyclic thermal load and,thereby,study the thermal erosion behavior of the Cr coating on the barrel’s inner wall,a laser emitter is utilized in the current study.With the help of in-situ tensile test and finite element simulation results,a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified.Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature.In this study,the interfacial ultimate shear strength decreases from 2.57 GPa(no erosion)to 1.02 GPa(laser power is 160 W).The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model.And this model is used to predict the flaking process of Cr coating by finite element method.The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.
文摘Two low alloy steels 0.5Cr-0.5Mo-0.25V and H85 were pack-aluminized at 900°for 4 h by using Fe-Al powder mixture containing 48% Fe, 20.6% Al- 29.4% Al2O3 and 2% NH4Cl by weight. The microhardness and oxidation resistance at 900℃ of the aluminide coatings were studied. It was found that pack-aluminizing improves the microhardness of the 0.5Cro.5Mo-0.25V steel while it reduces the microhardness of the H85 steel. Pack aluminizing highly improves the oxidation resistance after 20h exposure at 900℃ in air for the investigated steels.
文摘Silicone coatings have been used in this study. The method adopted was the liquid drop analysis on the coated fabrics. The contact angle between a liquid drop and the fabric surface was measured with two liquids continuously and recorded by a computer. The surface energy was calculated by means of Owens method.Kinetic measurement was adopted. The contact angle of liquids on the fabric coated silicone decreased with time was found. A compound solution DX has been found, so that the contact angle of the liquids on the fabric washed with DX becomes constant, and the surface energy of the fabric can be reduced to below 15 mJ/m2.
文摘Samples of the cross section microstructures of galvannealed steel sheets that lack alloying were analyzed. X-ray diffraction (XRD) tests were carried out. The study discovers that the deficit of alloying was higher on both sides of the steel sheet when compared to the center and the thickness of the coating on the sides was also higher than the center. The results of the XRD tests demonstrate that the microstructure of the coating with a lack of alloy is mainly composed of zinc,ζ and δ. They also indicate that the lack of alloying is mainly due to a lower galvannealing temperature and thicker coating. It is shown by the optical micrographs of coating that the δ phase forms first in a discontinuous manner at the interface and then rapidly pushes towards the coating and enlarges.
文摘Zn-Mg alloy coatings were obtained by physical vapor deposition (PVD) on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction (XRD) ,scanning electron microscope (SEM) and glow discharge optical emission spectrometry (GDOES). It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.
文摘Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating. The effects of surface roughness on the surface lubrication performance of the steel sheets were examined using a friction coefficient tester. Results revealed large dynamic friction coefficients for the galvanized steel sheets, which increased remarkably with surface roughness. Once the self-lubricated coating was applied, significant drops in the dynamic friction coefficients were measured. After the first stage of the friction test,the coefficients were almost unchanged, which reflected a weak dependence on the surface roughness of the self-lubricated steel sheets. However, the dynamic friction coefficients gradually increased as the test progressed, where these increase clearly correlated with the surface roughness of the self-lubricated steel sheets.
文摘Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.
文摘This paper presents the results of experimental work carried out in dry turning of cast duplex stainless steels (ASTM A 995 Grade4A and ASTM A 995 Grade5A) using TiC and TiCN coated cemented carbide cutting tools. The turning tests were conducted at five different cutting speeds (80, 100, 120, 140 and 160 m/min) and three different feed rates (0.04, 0.08 and 0.12 mm/rev) with a constant depth of cut (0.5 mm). The influence of cutting speed and feed rate on the machined surface roughness was investigated. Texture analysis (Bulk) was also carried out to study the impact of preferred orientation on the resulting surface roughness. The result reveals that the increasing cutting speed decreases the surface roughness till a particular point and then increases whereas;the surface roughness value decreases with the decreasing feed rate. Presence of alpha fiber (Bulk texture analysis) in the austenite phase of 4A work piece material leads to better surface finish. Among both the grades, surface finish of grade 4A is better than grade 5A work piece material.
文摘Al coated steel sheets with excellent heat resistance,thermal reflection,and corrosion resistance are widely used in various applications.The laser weldability of the Al coated steel sheet for full penetration welding was reported.The phenomenon caused by intermixed aluminum and behavior of aluminum in the weld were investigated.Al coated steel sheets that have various thickness and coating mass were prepared for laser welding.The effects of parameters such as welding conditions and Al coating conditions were investigated.Al content mixed in the weld after laser welding was evaluated,and then a correlation between the mixed Al and mechanical properties was investigated.The results show that the Al-rich zones which have Fe-Al intermetallic compounds are found in the weld.The intermetallic compounds cause the decreased strength of the weld.
基金Project supported by Grants-in-Aid for the National Core Research Center Program from MOST/KOSEF
文摘The flow characteristics of aluminum coated boron steel in hot press forming were investigated.Furthermore,the effects of aluminum coated layer on press forming were analyzed during deep drawing.The results show that aluminum coated boron steel exhibits a high sensitivity on temperature and strain rate.Aluminum coating layer appears in surface flaking in a temperature range of 700-800 ℃,but smooth surface is formed above 900 ℃.