Microstructure characteristics of Ni/WC composite cladding coatings

A multilayer tungsten carbide particle（WCp）-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology.The morphology,microstructure,and formation mechanism of the coating were studied and discussed in different zones.The microstructure morphology and phase composition were investigated by scanning electron microscopy,optical microscopy,X-ray diffraction,and energy-dispersive X-ray spectroscopy.In the results,the coating presents a dense and homogeneous microstructure with few pores and is free from cracks.The whole coating shows a multilayer structure,including composite,transition,fusion,and diffusion-affected layers.Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers.The Ni-based alloy is mainly composed of y-Ni solid solution with finely dispersed Cr7C3/Cr（23）C6,CrB,and Ni＋Ni3Si.WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles,forming a special three-dimensional reticular microstructure.The macrohardness of the coating is HRC 55,which is remarkably improved compared to that of the substrate.The microhardness increases gradually from the substrate to the composite zone,whereas the microhardness remains almost unchanged in the transition and composite zones.

Cu-Al interfacial compounds and formation mechanism of copper cladding aluminum composites

Copper cladding aluminum(CCA)rods with the section dimensions of12mm in diameter and2mm in sheath thickness were fabricated by vertical core-filling continuous casting(VCFC)technology.The kinds and morphology of interfacial intermetallic compounds(IMCs)were investigated by SEM,XRD and TEM.The results showed that the interfacial structure of Cu/Al was mainly composed of layeredγ1(Cu9Al4),cellularθ(CuAl2),andα(Al)+θ(CuAl2)phases.Moreover,residual acicularε2(Cu3Al2+x)phase was observed at the Cu/Al interface.By comparing the driving force of formation forε2(Cu3Al2+x)andγ1(Cu9Al4)phases,the conclusion was drawn that theε2(Cu3Al2+x)formed firstly at the Cu/Al interface.In addition,the interfacial formation mechanism of copper cladding aluminum composites was revealed completely.

Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding

A novel approach to produce an intermetallic composite coating was put forward.The microstructure,microhardness,and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction （XRD）,scanning electron microscopy （SEM）,energy dispersive spectrum （EDS） analysis,microhardness test,and ball-on-disc wear experiment.XRD results indicate that some new phases FeAl,Fe0.23Ni0.77Al,and Ni3Al exit in the composite coating with the Al2O3 addition.SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures.The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating.The formation mechanism of the intermetallic compounds was also investigated.

Fabrication of Fe–TiC–Al_2O_3 composites on the surface of steel using a TiO_2–Al–C–Fe combustion reaction induced by gas tungsten arc cladding

The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon steel.For this purpose,TiO2-3C and 3TiO2-4Al-3C-xFe（0 ≤ x ≤ 4.6 by mole） mixtures were pre-placed on the surface of a medium carbon steel plate.The mixtures and substrate were then melted using a gas tungsten arc cladding process.The results show that the martensite forms in the layer produced by the TiO2-3C mixture.However,ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C mixture.The addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt%increases the volume fraction of particles,and a composite containing approximately 9vol%TiC and A12O3 particles forms.This composite substantially improves the substrate hardness.The mechanism by which Fe particles enhance the TiC ＋ A12O3 volume fraction in the composite is determined.

Horizontal continuous casting process under electromagnetic field for preparing AA3003/AA4045 clad composite hollow billets

A modified horizontal continuous casting process under the electromagnetic field was proposed for preparing AA3003/ AA4045 clad composite hollow billets. To investigate the effect of electromagnetic field on this process, a comprehensive three-dimensional model was developed. Two cases with and without electromagnetic field were compared using the simulations. When rotating electromagnetic stirring is applied, the flow pattern of fluid melt is greatly modified; the mushy zone becomes much wider, the temperature profile becomes more uniform, and the solid fraction decreases for both the external and internal alloy melt layers. These modifications are beneficial for the formation of a bimetal interface and fine and uniform grain structure of the clad composite hollow billet. Experiments conducted using the same electrical and casting parameters as the simulations verify that under the electromagnetic field the microstructure of the clad composite hollow billet becomes fine and the diffusion of the elements at the interface is promoted.

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.

Casting-cold extrusion of Al/Cu clad composite by copper tubes with different sketch sections

Casting-cold extrusion technology was presented to fabricate alttminum/copper clad composite, and copper tubes with different sketch sections were designed. The technology of aluminum/copper clad composite fabricated by casting-cold extrusion was simulated by DEFORM software using tubes with four arc grooves. The stress and strain in different deformation zones were analyzed. The groove size reduces gradually and the groove shape drives to triangle during the extrusion procedure. The maximum values of equivalent effective stress and radial stress appear in groove zones, and the maximum equivalent effective strain firstly is obtained also in groove zones. The grain size in groove zones is less than that in other zones. The experimental results are consistent with simulation results, which prove that the copper tubes with sketch section are favorable to the metallurgy bond of boundary interface between aluminum and copper.

Effect of silicon content on microstructure of Al-Si/SiC_p composite layer cladded on A380 Al alloy by TIG welding process

Tungsten inert gas（TIG） welding was applied to creating a composite layer on the surface of cast aluminum alloy A380. Different mixtures of Al, Si and SiC powders mixed with sodium silicate solution were pasted on substrates. Surface melting was conducted by TIG welding to produce Al-SiC layer on the surface. Microstructural evolution was investigated by X-ray diffractometry（XRD）, optical and scanning electron microscopy（SEM） and elemental microanalysis（EDS）. Properties of clad layers were studied by microhardness and sliding wear testing. The results showed a uniform distribution of SiC particles in dendritic aluminum matrix. Addition of excess silicon caused the formation of eutectic crystals and coarse silicon particles in the clad layer which resulted in higher hardness and wear resistance of clad layers.

Comparative Moisture Performance of Wood/Wood-Based Claddings Predicted by Four Hygrothermal Simulation Tools

A number of hygrothermal(HAM)numerical simulation packages are available,either wholly or partially dedicated to heat,air and moisture transfer simulations of building materials and wall assemblies.The objective of this work was to compare the HAM responses and moisture performance of western red cedar and composite wood claddings of a wood frame wall as predicted by four HAM simulation tools:DELPHIN,WUFI,hygIRC,and COMSOL.Three Canadian cities having different climates were selected for simulation:Ottawa(ON),Vancouver(BC)and Calgary(AB).In each city,simulations were run for two years as selected from a historical climate data set based on the moisture index(MI).The wall orientation receiving the most wind-driven rain for the two years was selected for simulations.Material properties were taken from the National Research Council(NRC)material property database.Cladding temperature and relative humidity(RH)values as well as the moisture accumulated in the entire structure were compared amongst the results obtained from the four tools.The mold growth index on the cladding surface was used as a basis for comparing the moisture performance.

Interface evolution of Cu-Ni-Si/Al-Mg-Si clad composite wires after annealing

Interface micros tructures of Cu-Ni-Si/Al-MgSi clad composite wires during isothermal annealing from 623 to 773 K were investigated.The composite wires were fabricated by a drawing process.The evolution of intermetallic compounds(IMCs)was analyzed.A continuous IMCs layer forms only after annealing for 1 min,which may be due to more IMCs nucleation points generated by deep drawing process.IMCs consist of Al_(4)Cu_(9),AlCu and Al_(2)Cu identified by energy-dispersive spectroscopy(EDS)and transmission electron microscopy(TEM).The growth activation energies of total IMCs,Al_(2)Cu,AlCu and Al_(4)Cu_(9),are 98.8,69.4,101.3 and 137.1 kJ·mol^(-1),respectively.The higher growth activation energy of Al_(4)Cu_(9)results in the higher growth rate under high temperature.However,the average interdiffusion coefficient for each IMC calculated by Wagner method shows that interdiffusion in Al_(2)Cu and AlCu is more active than that in Al_(4)Cu_(9).The higher growth rate of Al_(4)Cu_(9)may be caused by the long concentration range.