Interfacial behaviors of epoxy asphalt surfacing on steel decks

A model for predicting the interface behavior of epoxy asphalt and steel composite beam under negative bending is developed incorporating partial interaction theory. Interfacial slips between the steel deck and the epoxy asphalt surfacing are included in the model with a new parameter of membrane stiffness. A series of analytical equations based on this model are derived to calculate slip and strain at the interface. Also, a numerical procedure for calculating the load responses of simply supported composite beams with concentrated force at the mid-span is established and verified with two samples. Characters of slip and strain at the interface, sensitivities of tensile stress and interface shear stress with material parameters are studied. It can be concluded that interfacial effects decrease the bending stiffness of the composite; hard and stiff bonding material is better for asphalt surfacing layer working at normal to low temperatures, and the damage of the asphalt surfacing layer will be accelerated with the damage accumulation of the bonding coat.

Resin-Surfacing复合型树脂碎石在润扬大桥钢桥面的运用

我国当前正处于大跨径桥梁建设的高峰期,同时面临大跨径钢桥面铺装养护期,如何提高桥面铺装管养水平,关系到钢桥面铺装的使用寿命。依据对润扬大桥钢桥面早期出现的裂缝等病害采用ResinSurfacing复合型树脂碎石的工艺,对在实际操作及取得的经验做具体的介绍,以期对类似钢桥面环氧早期养护带来一定参考。

Effects of parameters of asphalt concrete surfacing on mechanical property of paving layer

The important parameters that influence the mechanical property of the pavinglayer on an orthotropic steel bridge deck are the paving layer thickness and modulus of the asphaltconcrete surfacing. Three important indices that control the typical failures of the paving layerare the maximum tensile stress of paving layer, the maximum shear stress between the steel deck andthe paving layer, and the maximum deflection on the paving surface. In this paper, the analyticalmodel of paving systems on orthotropic steel bridge deck is established, and the finite elementmethod is adopted to study the stress and strain of paving system. With the variation of asphaltconcrete modulus in high or low temperature season, the influences of paving layer thickness onthree control indices are researched. The results provide a theoretical basis for the determinationof thickness of the paving layer on the steel bridge deck.

Microstructure and wear characterization of AA2124/4wt.%B4C nano-composite coating on Ti-6Al-4V alloy using friction surfacing

This work is focused on developing AA2124/4 wt.%B4 C nano-composite coatings on Ti-6 A1-4 V using friction surfacing to improve the wear resistance. The composite was produced using conventional stir casting method and coatings were laid using an indigenously-developed friction surfacing machine. The rotational speed of the mechtrode was varied. The microstructure of the composite coating was observed using conventional and advanced microscopic techniques. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The coating geometry(thickness and width) increased with increased rotational speed. The interface was straight without thick intermetallic layer. Homogenous distribution of nano B4C particles and extremely fine grains was observed in the composite coating. The interfacial bonding between the aluminum matrix and B4C particles was excellent. The composite coating improved the wear resistance of the titanium alloy substrate due to the reduction in effective contact area,lower coefficient of friction and excellent interfacial bonding.

Influence of magnetic field on microstructure and properties of Ni60 plasma surfacing layer

In order to control the shape and distribution of hardening phase in plasma surfacing deposit, a longitudinal DC magnetic field was applied during plasma surfacing of nickel-based alloy Ni60. Hardness, wearing resistance, microstructure and phase coastitnent of the plasma surfacing layer were investigated. It was revealed that the hardness and wearing resistance of the Ni60 plasma surfacing layer could gotten significantly enhanced through introducing magnetic field. The mechanical properties of the surfacing deposit were optimal when magnetic field current is 1 A. The metallurgical analysis showed that the microstructure of the Ni60 plasma surfacing layer was mainly composed of γ solid solution and some hardening phase particles such as Cr7C3 with an application of the magnetic field.

Effects of alloy elements on microstructure and crack resistance of Fe-C-Cr weld surfacing layer

Effects of alloy elements on the microstructure and crack resistance of Fe-C-Cr weld surfacing layer were investigated. The results show that microstructures of the layer mainly consist of carbides and austenite matrix. Increasing C and Cr contents impair the crack resistance of the layer due to increased amount of brittle carbides. The addition of Ni, Nb or Mo improves the crack resistance of Fe-C-Cr weld surfacing layer by increasing the amount of austenite and forming fine NbC or M 7C 3 carbides in the layer. But, the excessive Nb (>2.50wt%) or Mo (>1.88wt%) impairs the crack resistance of the layer, which has relation with increased carbides or carbide coarsening and austenite matrix solid solution strengthening. The proper combination of C, Cr, Ni, Nb and Mo can further improve not only the crack resistance of Fe-C-Cr weld surfacing layer but also the erosion resistance as a result of fine NbC and M 7C 3 carbides distributing uniformly in austenite matrix. The optimal layer compositions are 3.05wt%C, 20.58wt%Cr, 1.75wt%Ni, 2.00wt%Nb and 1.88wt%Mo.

Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe-C-Cr Weld Surfacing Layer

Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).

Thermal behavior of B_4 Cparticles under plasma arc powder surfacing condition

The effect of plasma arc powder surfacing process on the amount of B4C particles in the coating and the thermal behavior of B4C particles in different surfacing stages has been investigated.The results showed that the feeding rate of B4C partiles is the most important factor affecting the amount of B4C particles in the surfacing coating among all the surfacing parameters,and the most part of B4C Particles in the coating is nto the remainders of original solid B4C particles,but the consolidation products of the unmelted liquid B4C globules in the pool.The results also showed that the B4C particles would not be melted in the plasma arc column, their melting process mainly takes place in the anode spot region on the surface of the pool when surfacing current is less than 200A.

FORMATION OF GRADIENT COATING OF Fe-BASED ALLOY WITH RARE EARTHS BY PLASMA SURFACING

A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3, Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.

Influence of rotational speed in friction surfacing of nickel-aluminide reinforced aluminum matrix composite on commercially pure aluminum

The effect of rotational speed in the friction surfacing of nickel-aluminide reinforced Al-Zn-Mg-Cu alloy matrix composite on commercially pure aluminum was investigated. The nickel-aluminide reinforcement was fabricated by in-situ methods based on adding nickel powders to Al-Zn-Mg-Cu alloy melt during the semi-solid casting process.The findings showed that an increase in the rotational speed from 600 to 1000 r/min raised the coating efficiency from 65% to 76%. Besides, there was no significant difference between coating efficiencies in the coating with and without nickel-aluminide. The outcomes showed that if the coating was applied at a rotational speed of 1000 r/min, a traverse speed of 100 mm/min, and an axial feeding rate of 125 mm/min, the hardness and shear strength of the substrate increased by up to 225% and 195%, respectively. But the wear rate of the substrate dropped by 75%. Although the hardness of the coating containing nickel-aluminide increases by up to 32% compared to the coating without nickel-aluminide, nickel-aluminide does not affect the thermal stability of the coating.

Preparation and Characterization of Ni60-Cr_3C_2-WC/TiC Plasma Welding Surfacing Layer

Using plasma build-up welding technology, Ni60, WC, Cr3C2, and TiC composite powders were clad on the surface of the substrate in a certain proportion according to the metallurgical bonding method to increase the bond strength between the coating and the substrate. Scanning electron microscopy and energy dispersive spectroscopy were used to observe the microstructure of the surfacing layer and the chemical composition of the sample. The hardness and wear resistance of the surfacing layer were tested and analyzed by the HV-1000 hardness tester and the impact wear device. The results showed that in the microstructure, fishbone, spider-web, and floral-like structures appeared in the surfacing layer. When the micro-hardness was tested, the depth of the indentation reflected the hardness of the surfacing layer. When analyzing wear resistance, the amount of wear increases with time.

SURFACING ELECTRODE WITH CRACKING RESISTANCE AND WEARABILITY

A new surfacing electrode is developed with cracking resistance andwearability based on high microhardness of TiC and VC, carbides of Ti and V are formed in depositedmetal by means of high temperature arc metallurgic reaction. The results show the hardness ofsurfacing metal increases with the increase of ferrotitanium (Fe-Ti), ferrovanadium (Fe-V) andgraphite in the coat. However, when graphite reaches the volume fraction of 11 percent, the hardnessreaches its peak value, and when beyond 11 percent, the hardness falls off. As Fe-Ti, Fe-V andgraphite increase, the cracking resistance of deposited metal and usability of electrode declines.Carbides are dispersedly distributed in the matrix structure. The matrix micro structure ofdeposited metal is lath martensite. Carbides present irregular block. When using the researchedsurfacing electrode to continue weld with non-preheated, no seeable crack or only a few micro-crackscan be observed in the surface of deposited metal. The hardness is above 60 HRC. The wearresistance is better than that of EDZCr-C-15.

Erosion resistance of Fe-C-Cr weld surfacing layers

Fe C Cr weld surfacing layers with different compositions and microstructures can be obtained by submerged arc welding with welding wire of the low carbon steel and high alloy bonded flux. With the increase of Cr and C in the layers the microstructures are changed from hypoeutectoid steel, hypereutectoid steel to hypoeutectic iron and hypereutectic iron. When the weld surfacing layers belong to the alloyed cast irons the erosion resistance can be raised with the eutectic increase and the austenite decrease. Good erosion resistance can be obtained when the proportion of the primary carbides is within 10 %. The experimental results lay a foundation to make double metal percussive plates by surfacing wear resistant layers on the substrates of the low carbon steels.

Friction surfacing of AISI 316 over mild steel: A characteriation study

An attempt has been made with overlaying of stain-less steel on mild steel by the technique of friction surfacing. This investigation elaborates the excellence acquired by different combination of the process parameters used in friction surfacing specifically traverse speed of the cross slide, speed of rotation of the spindle and the uniaxial compressive load. Excellent overlaying has been obtained amongst the chosen materials. To which, the coating can be done with various set of process parameters. It has been observed that the bond strength of the coating was found to be at a maximum of 502 MPa by ram tensile test.Based upon this results the surface methodology was characterized with scanning electron microscope.For authenticating the results, the coated specimen was subjected to salt spray test. The bonding microstructure was characterized using optical microscopy and X-ray diffraction. Corrosion resistance of surfaced coatings was found to be more inferior to that of mechtrode material and greater with the substrate.

THE DEVELOPMENT OF COLD WELDING SURFACING ELECTRODE FOR BLAST FURNACE VALVE

The Authors of this Article have done research on the cracking resistance of cold welding surfacing electrodes for blast furnace valves by adjusting the basicity of slag component, decreasing the hydrogen content and improving microstructure. The DF 2 Cold Welding Surfacing Electrodes prove to possess the following characters: 1) Excellent cracking resistance for surfacing alloys at normal temperature. 2) Excellent cracking resistance for repair welding and rewelding. 3) Excellent machinability for surfacing alloying.

Effect of Temper Temperature on Microstructures and Wear Resistance of Surfacing Deposits of Ferro-Base with Cr-W-MO Alloy

In the paper, the effect of temper temperature on microstructures and wear resistance of surfacing deposits of Ferro-base with Cr-W-MO alloy were investigated. The results show that the secondary hardening can be obtained when the surfacing deposits is tempered. Temper temperature is lower than 400 ℃, the hardness of surfacing deposits of Ferro-base with Cr-W-MO alloy has little change, when it exceeded 600 ℃, the hardness decreases obviously, the surfacing deposits tempering at 560 ℃ for 2 h has excellent wear resistance. As a result, the microstructure of surfacing deposits is in relation to its wear resistance.

Joining and surfacing of advanced materials

The application of advanced materials, i.e. advanced ceramics, glasses, intermetallic phases and various type of composites, not only depends on their manufacture processes including a great input of know-how, but also on their abilities for processing, among which the joining processes play an important role. The uses of advanced materials are changing rapidly, with a major emphasis on technical applications, especially the components of machines, apparatus and technical devices expected to withstand very heavy exploitation conditions. Furthermore,these materials are becoming more complex, in terms of being strengthened and toughened by transformation processes as well as by the addition of other ceramic or metallic materials including nanomaterials. The successful use of advanced materials requires the development of equally advanced joining materials, processes and technology. Some selected examples of results of joining advanced materials with the use of various procedures as well as surface modification of structural components with the use of advanced materials obtained in the Welding Engineering Department of Warsaw University of Technology, Poland, are presented.

QUANTITATIVE ANALYTIC TECHNOLOGY OF ULTRA-HARDNESS AND WEAR RESISTENT SURFACING MATERIAL

Mathematical models between surfacing welding properties of C, Cr, Mo, V, W alloy system and encode factors of alloy additives are established by test methods of advanced trial optimizing technology and computer assistant design (CAD). They help to draw unitary functions and binary isoclines diagrams through which the influence of encode factorial linearity, nonlinear effect and factors interaction of alloy additives on the performances of surfacing welding can be analyzed directly and quantitatively. Meanwhile, the performances of deposited metal can also be predicted according to the content of alloy additives.

Effect of RE Oxide on Impact Toughness and Primary Structure of Surfacing Metal

The effect of rare earth(RE) oxide on impact toughness and primary structure of surfacing metal was investigated . The results show that the impact toughness of surfacing metal containing RE oxide can be increased by 50 %. The primary structure can be refined and its shape changed from columnar crystals to equiaxed ones.

Characteristic of Bond Zone between Powder Surfacing Layer and Base Metal

The characteristic of the bond zone between Ni-based alloy light beam surfacing layer(SL)and base metal(BM)was investigated by scanning electron microscope,energy dispersive spectrometer and X-ray diffraction.The results show that the bond zone,which consists ofγ-Ni orγ-(Fe,Ni)planar crystal band close to SL andα-Fe bright band close to heat affected zone(HAZ),is actually the transition zone of composition and microstructure between SL and HAZ,and the metallurgical bond interface lies between theα-Fe bright band and HAZ.With the increase of light beam heat input from 2kJ/mm to 4kJ/mm,the width of the bond zone increases from 4μm to 15μm,and the morphology of bond interface changes from zigzag to straight.The formation of bond interface indicates the formation of reliable metallurgical bond between SL and BM.