Showing papers in "Materials protection in 2004"

Detonation Spraying Nano WC-Co Coatings

Abstract: Nano - phased and coarse - grained WC- 12Co coatings were deposited by detonation spraying. The microstructures of two coatings were analyzed by using metallograph and SEM. The microhardness and grinding wear resistance were tested on the microhardness scale and ML-10 tester,and the morphologies of worn surface were also observed by using SEM. It is shown that the density and microhardness of nano - phased coating are higher than that of coarse - grained coating, and the distribution of WC in the coating is more homogeneous. The wear of nano-phased coating is microcutting mechanism, and the grinding wear resistance is lower than that of coarse-grained coating.

Interpretation Model of Sandelin Effect Mechanism in Hot Dip Galvanizing

Abstract: Sandelin effect that describes the influence of silicon content in steels on the hot-dip galvanizing has been studied for many years, but a fundamental understanding of the phenomenon is still lacking. Up to date, there are three main models as Γ modification, J. Foct' s hypothesis and hydrogen evolving model. Γ modification associates the abnormal growth of coating on the steel containing silicon with the modification of Γ phase. It supposes that patch Γ grains carry silicon into ζ layer to trigger the formation of bearded structure. J. Foct' s hypothesis relates the abnormal coating to liquid zinc containing super- saturated silicon existing near the steel substrate. Hydrogen-evolving model conjectures that the Si content in steel does not influence the galvanizing process directly but indirectly by affecting the diffusion of hydrogen in the steel. Although the three models can interpret some phenomena of Sandelin effect for their own advantages, further research should be done.

Wear Resistance of Ni-P-AI_2 O_3 Composite Electroless Plating

Abstract: Combining the Al_2O_3 particles with Ni-Pelectroless plating solution, the wear resistance of plating can be improved by evenly scattering Al_2 O_3 particles in Ni- P matrix.The effects of process conditions and after heat treatment temperature on the wearability of composite electroless plating were investigated. Experiment results show that the plating technologies have influence on the plating speed and Al_2 O_3 distribution in coating,and heat treatment after electroplated can raise the hardness of coating. Under the condition of pH 5.4, temperature at 90±2℃,stirring speed is 400 r/min with addition of 5 g/L α-AI_2O_3 particle ,the wearability of coating is the best through one hour heat treatment at 400℃. In the same of wearing condition, the wear resistance of composite coating raises 6～7 times than Ni-P coating, and over 3O times than 45 steel in quenching state.

Preparation Technology and Properties of Nickel-Tungsten- Titanium Dioxide Composite Plating

Abstract: In order to further improve the electrocatalytic activity of nickel- tungsten alloy plating for hydrogen evolution, the nickel-tungsten -titanium dioxide composite plating was prepared by electrodepo- sition, and its electrocatalytic properties for hydrogen evolution reaction were studied in alkaline solution by means of cathodic polarization curve, AC impedance technique as well as surface corrosion morphology of electrodes were observed using SEM The experimental results show that the introduction of titanium dioxide into the Ni- W alloy increases the specific surface area of alloy e- lectrode, and changes the hydrogen evolution mechanism The Ni-W-TiO_2 composite coating has high electrocatalytic activity for hydrogen evolution reaction and can be used as active elec- trode for electrolytic water reaction

Relationship Between Microstructure and Corrosion Resistance of Q235 Steel Treated by Low Temperature Gas Multicomponent Thermochemical Treatment Technology

Abstract: Q235 steel sample was treated by low temperature gas muhicomponent thermochemical treatment technology. Then the corrosion resistance of steel sample was tested and the microstructure was also analyzed. The relationship between the corrosion resistance and microstructure was discussed by using space group and thermodynamics theories. Results indicate that the corrosion resistance of Q235 steel treated like that is improved greatly and can be improved further when the elements N and S are dissolved into Fe-N compound. The reason is that S and N elements can reduce the free electrons on the sample surface and enhance the potential of compound.

Effect of Methanol and Butanol Etherized Amino Resin Curing Agent on Acrylic Cathodic Electrophoretic Coating

Abstract: Application of amino resin curing agents in cathodic electrophoretic coatings is limited for its poor stability in the bath. Amino resin curing agents with different etherization degree were prepared by etherizing hexahydroxymethyl melamine using methanol and butanol,and its application in acrylic cathodic electrophoretic coatings was studied.The results show that the amino resin with appropriate etherization degree can gain the coating with excellent properties,and keep the stability of electrophoretic solution.

Corrosion and Protection of Copper Tubes in Condenser of Heat Power Plant

Abstract: Corrosion situation of copper tubes in condenser of power plant was introduced Corrosion patterns of brass tubes are mainly dezincification corrosion, stress corrosion crack and erosion corrosion, and their corrosion mechanisms and protection methods are also presented Essential protection method for copper tubes, ferrous sulfate filming technology, was suggested as reference to control corrosion of copper tubes in power plant

Effect Factors of Eleetroless Silver Plating on Nonmetallic Powder

Abstract: Agcoated nonmetallic powder materials can be used as conductive fillings mmany industrial fields.The effect factors such as additives PEG.CMC and gelatin and pH values were studied in the process of eleetroless silver plating on glass microspheres.The plating rate curves and SEM morphologies of Ag coating were analyzed and discussed.Results show that both PEG and EtOH can improve the quality of the Ag coating and PEG is in particular, but CMC and gelatin are counteractive. The better pH value is 13.5.Effect mechanisms are presented.Ag coating with higher quality can be obtained by using PEG and EtOH as compound additive and pH = 13.5.

Relation Between Corrosion Rate of Brass and Concentration of Chloride Ion

Abstract: In order to quantitative determine the relation between brass corrosion and concentration ofCl~-, static coupon test was carried on for two kinds of brasses HSn70-1A and HA177-2A, and experimental data was fitted into curve.The results make clear that there are both cubic relations between corrosion rates of two brasses and C1-concentration, the difference lies in that the corrosion rate change of HSn70-1A brass with C1-concentration is more obvious than HA177-2A, so HSn70-1A brass is more sensitive to corrosion of C1 than HA177-2A brass.

Development of Hypersonic Flame Spraying Technology

Abstract: One new hypersonic flame spraying technology,activated combustion high-velocity air-fuel spraying technology (AC-HVAF),was introduced.The technology has litter oxidation and thermal deterioration effects on the spraying material,can obtain very high impact coatings with extremely low oxide content,which has excellent wear and corrosion resistances.Besides its spraying rate and deposition efficiency are better than conventional hypersonic flame spraying technology (HVOF).

Development of Temper Rolling Liquor for Single Stand and Double Stands

Abstract: To meet the multi-functional requirements of temper roll- ing liquor in the cold roiling mill of WISCO, some dozens of addi- tives was selected individually or in combination fer performance tests. The chosen temper roiling liquor is composed of water-sol- uble rust inhibitors such as carboxylate, fatty amine salt, hetero- cyclic organics and benzoate, cleaning additives such as polyoxy- ethylene nonionic surfactant and fatty acid sah anionic surfactant, and film formers such as high molecular oligomer. The results of laboratory systematical evaluation and industrial application show that YX- 3 temper rolling liquor is nitrite free, and its rust- pre- venting is superior to homogeneous British product for cold rolled steel sheet and galvanized sheet. The YX-3 liquor with good cleaning property and favorable lubricity is compatible with elec- trostatic spraying antirust oil in the finishing process, and is suit- able for single stand and double stands.

Influence Model of Parameters on Thickness of Coating in Micro-Arc Oxidation Process

Abstract: Technological parameters of micro - arc oxidation (MAO) affect the thickness of coating, which affects the performances of treated casting directly. Based on the equivalent circuit of MAO process, a theoretical model was established to investigate the influences of process parameters on the thickness of coating. The parameters included electrical voltage, electrical current and the electrolyte. The analysis results of model show that the thickness of coating increases with the increase of electrolytic conductance and processing time. The thickness increment rate of coating in the early stage of processing is greater than the later stage, and is proportional to the voltage increment rate under the condition of gal-vanostat. All the analysis results agree with the experimental results from others.

Preparation of Fly Ash Cenospheres Coated M-BaFe_(12)O_(19)by Sol-Gel

Abstract: Ferrites are widely used in microwave absorbing materials.Because of its large density unsuitable for light absorbing materials with wide absorbing waveband and thin thickness,ferrites are often prepared as composite-ferrite-absorber.Fly ash cenospheres coated barium hexaferrite were prepared by sol-gel using Fe(NO_3)_3·9H_2O,Ba(NO_3)_2and citric acid as raw materials.The cenosphere particles were characterized by differential thermal analysis,X-ray diffraction analysis,scanning electron microscope,and energy dispersive spectroscopy during and after the coating process.The results show that even and continual barium hexaferrite coating is prepared on fly ash cenosphere by sol-gel.

Evaluation Method on Reflectivity of Solar Reflective Coating and Mathematic Model

Abstract: Solar reflective coating is a kind of functional coating that can reduce the temperature increase because of solar radiation. Had improved the testing device and method for reflectivity determination of coating, the reflectances of different solar reflective coatings were measured, and a corresponding mathematic model was built with reliability proof. The model can be used to compare the solar reflective relatives of different solar reflective coatings. Diffuse reflectance spectrophotometer with an integrating sphere was used to measure the reflective index, and the temperature changing curve of oil tank in real atmosphere was simulated. The results proved that the method and mathematic pattern are correct. The reflectivity of a new solar reflective coating based on the method is obviously higher than ouher normal coatings in the wavelength region of 200～2 600 nm, and has better effect of temperature drop.

High Temperature Oxidation Resistance of RE-Ni-W-P-SiC Pulse Composite Electroplating

Abstract: A little attention is paid to the RE-Ni-W-P-SiC coating and its high temperature resistance.Oxidation resistance of pulse electrodeposited RE-Ni-W-P-SiC composite coating was studied by oxidation weight increment and X-ray diffraction pat-terns.The results show that the oxidation resistance of pulse composite coating is better than that of direct current composite coatrag.The oxidized film weight of RE-Ni-W-P-SiC pulse composite coating increases with the rise of oxidation temperature and the extend of oxidation time, and the film weight increment is little when oxidation temperature is less than 800～℃, but the oxidized film weight increment is rapid when oxidation temperature is more than 800 ℃.The pulse frequency (f) and duty ratio (r) have important effect on the oxidation resistance.As a whole, the resistance of coating is better while f is 33 Hz and r is 0.4 or 0.6.With the increase of heat treatment temperature and time, the amorphous structare of coating reduces, and the coating transforms to crystal gradually that the diffraction peak of Ni3 P phase enhances and new phases come into being unceasingly.The RENi-W-P-SiC pulse composite coating has better high temperature oxidation resistance.

Performance Improvement of TiN Ion Plating on 4Cr5MoV Steel with Rare Earth Element Cerium

Abstract: To solve the problems of TiN coating such as low adhesion and oxidation resistance, TiN coating with rare earth cerium was prepared on the 4Cr5MoV steel by using electrical arc ion plating and coating alloying technologies. the effects of rare earth Ce on the TiN and Ti (Al, V) N coatings were studied by measuring the microhard-ness, porosity, wearability and adhesion of coating as well as the constant temperature oxidation and heat vibration tests. The experiment results show that the addition of Ce can enhance the wear resistance of coating, and greatly increase the adhesion between coating and substrate, moreover improve the oxidation resistance and heat vibration resistance obviously. Rare earth Ce is significant in spreading the application of coatings on 4Cr5MoV hot working die steel.

Local Corrosion Behaviors of LY6 Aluminum Alloy in CI~- Environment

Abstract: Local corrosion behaviors of LY6 aluminum alloy after natural aging treatment in solution containing Cl~-,such as pitting corrosion, intergranular corrosion, exfoliation corrosion (EXCO) and stress corrosion cracking (SCC), were studied as well as their mechanisms and correlation LY6 aluminum alloy is susceptible to pitting corrosion, intergranular corrosion,EXCO and SCC in the testing environment, which is essentially due to the existence of second phases, such as S phase (Al_2CuMg) , θ phase (CuAl_2 ) and MnAl6 phase The exfoliation of alloy happens from original pitting to intergranular corrosion and with cooperation of stress By constant load tensile test and fracture analysis, SCC of LY6 aluminum alloy is owing to the anodic dissolution effect

Development and Properties of Reference Electrode for Electrochemical Corrosion in High Temperature and High Pressure Environment

Abstract: High performance Ag/AgCl reference electrode had been made for in situ investigation of electrochemical corrosion under the conditions of high temperature and high pressure (HPHT) by optimizing of chlorinating process, improving of sealing structure and adopting of saturated KCl solution to overcome the instability of imported HPHT reference electrode. Thus the electrochemical system of autoclave is perfect to achieve the corrosion measurement in simulating oilfield downhole environments of HPHT. Comparing of the electrochemical results in situ and simulation of HPHT environments, it is confirmed that simulation test is unsuitable for discussion of corrosion behaviors and mechanisms of tube steel in HPHT oil and gas well.

Pretreatment Process for Electroless Nickel Plating of Hollow Glass Microspheres

Abstract: Pretreatment technology such as coupling and activating was studied for electroless nickel plating of hollow glass microsphere,as well as the influent of coupling on activating effect was discussed.The optimal coupling conditions were determined by orthogonal test.Hollow glass microspheres coated nickel were obtained through optimized pretreatment process and electroless nickel plating.The microstructure and components,of nickel coatings were characterized by using SEM and EDS.Investigation discovers that adsorption ability of hollow glass microspheres for palladium is improved greatly by coupled treatment,which increases the active sites of microspheres during electroless plating and the coated nickel layer is complete and uniform and compact.

Anticorrosion Materials Resistant to Molten Zinc

Abstract: Development and prospects of anticorrosion materials resistant to molten zinc were summarized for the serious molten zinc corrosion problem of materials in the hot - dip galvani zing industry.

Microstructure and Corrosion Resistance of Microarc Oxidation Film on AZ91D Magnesium Alloy

Abstract: Corrosion resistance of AZ91D magnesium alloy is weak in air. In order to reveal corrosion mechanism and improve performance, the morphology, nficrostructure and phase composition of microarc oxidation (MAO) film on AZ91D magnesium alloy were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore the corrosion resistance of film was tested. Results show that the MAd film on AZ91D magnesium alloy contains three layers that are outer layer, middle layer and inner layer. Some small discharge pores lie in the outer layer. The middle layer is loose and thick. Inner layer is combined to metal substrate tightly. The MAd film is mainly composed of MgO, MgSiO_3, MgAI_2O_4 and Mg_3 (PO_4)_2 compounds. The microarc oxidation is proved to improve corrosion resistance of AZ91D after three -week immersion in 3% NaCI solutinn. There exist pitting corrosion on the oxide film for ninny small particles containing Si and P element richly on the surface are electrochenfically active sites easy to corrode.

Preparation of Cu/ Fiberglass Catalyst with High Activity and Its Property

Abstract: In order to reduce the production cost of iminodiaeetic acid and solve the low activity and poor effect of catalyst, high active Cu/fiberglass catalyst was prepared by electrodepositing and its crystal lattice constant and specific surface area were tested, which had 'applied in the production of iminodiacetic acid by dehydrogenation oxidation of diethanolamine.The.The results show that the self-made catalyst makes the percent conversion of iminodiaeetie acid achieving 99.4% and the selectivity reaching 98.7%, and it can be used 38 times at least.The Raney Cu/fiberglass catalyst has better activity,higher selectivity and longer life than Raney Cu catalyst, so that it is prospective to be the new generation catalyst for iminodiaeetic acid industry.

Effects of Process Conditions on Flight Velocity of Cr_3C_2-NiCr Particles in High Velocity Oxy-Fuel Spraying

Abstract: Effects of fuel gas flow, oxygen flow and spray distance on the flight velocity of Cr_3C_2-NiCr particles in high velocity oxy-fuel spraying were experimentally studied by thermal radiation method. Results show that the propane flow, oxygen flow and spray distance affect the particle velocity considerably. The velocity increment of in-flight particles is comparatively obvious while the propane flow increases from 37 L/min to 46 L/min and the oxygen flow from 368 L/min to 447 L/min. The moderate oxygen flow makes for comparative high velocity. With the increase of spray distance, the variation of in-flight particle velocity exhibits a convex curve, and the acceleration effect of particle occurs within 160 mm distanee from the nozzle.

Pure Nitrogen Ion Nitriding under Furnace Shut and N_2 Provided Intermittently

Abstract: According to basic theories of energy condition for pure N_2 molecule being disassemble active nitrogen atoms and the ion nitriding model with pure nitrogen, the new technique of ion nitriding with pure nitrogen under furnace shut and N_2 provided intermittently was studied, and the critical disassemble energy of N_2 molecule for ion nitriding with pure nitrogen was calculated and validated experimentally through measuring and analyzing the microstructure, component phase and hardness gradient of nitrided layers. Experimental results show that there exists a voltage threshold in the ion nitriding with pure nitrogen. Only when the voltage is high as 700 V or so, the technique will produce obvious nitriding effect. In the same nitriding time, the nitriding effect by the technique is better than the conventional ammonia ion nitriding.

Liquid Surface Conditioning Agent

Abstract: With the application of cathodic electrophoresis coating technology in car industry, as mating technology low zinc phosphatizing is also applied widely, before which the key process for uniform and particular phosphatizing coating is the activation of metal surface Presently industrial typical surface conditioning agent is solid powder, which easily results in dusty pollution and affect the quality of coating, aside its preparation needs high energy loss, strict temperature controlling and a long time A new liquid conditioning agent was developed to overcome the disadvantages by adopting colloid titanium and phosphate polyphosphate stability system The method has the characteristics of simple preparation, low energy loss, strong treating ability and more fine crystal The surface conditioning ability of liquid conditioning agent, which can keep activity for a long time and improve cooperative ability of phosphatized coating and organic coating, is superior to the powdery conditioning agent

Chemical Replacement Copper Plating

Abstract: Although the chem- ical replacement copper plating technology has been researched for many years, it has not got valuable industrial application as yet. Because there still exist several crucial technical problems, especially as the important basic copper plating on Fe Or Zn metal surface. The development history of chemical replacement copper plating was reviewed, and several more important mechanisms and technical processes of immersion plating copper were de- scribed. The application situations of above processes were also commented. At last, some possible chemical additive that could be used in the future were presented.

Effect of Temperature on CO_2/H_2S Corrosion Rate of Oil Tube Steels

Abstract: CO_2/H_2S corrosion behaviors of oil tube steels N80 and P110 at different temperature (80, 90, 100, 110℃) were studied in an autoclave together with weight loss method and SEM. The results show that serious CO_2/H_2S corrosion occurs on both steel N80 and steel P110 in the range of testing temperature. With the increase of temperature, the corrosion rates increase at first and then decrease, and the maximum appear at 90℃ for both steels. The corrosion rates of steel P110 are always higher than steel N80.

Corrosion and Protection of Earth Screen in Transformer Substation

Abstract: To study the corrosion of grounding grids in transformer substation, the constitutes, pH and moisture of soil and reducing resistance reagent in transformer substation were measured by chemical analysis, and the pitting corrosion on A3 steel grounding electrodes scraped off zinc plating in reducing resistance reagent was observed in lab. Factors effecting corrosion behavior of grounding grids were investigated. Cl~- in the reducing resistance reagent is the key for the corrosion of earth screen. The pitting corrosion potential and corrosion potential of A3 steel electrode in soil containing of 4% NaCl move positively by adding some corrosion inhibitors such as NO~-_3, CO~(2-)_3, PO~(3-)_4, SiO~(2-)_3. Adding inhibitors as PO~(3-)_4 and SiO~(2-)_3 to the reducing resistance reagent can decrease the corrosion of earth screen.