The Microstructures And Properties Of Surface Layers By TIG Cladding Fe And Ni On Aluminum Substrate

The aluminum and aluminum alloy possess the excellent performances of highspecific strength，excellent electrical conductivity and thermal conductivity，but theabrasion usually occurs for the poor shortcomings of low hardness and relative wearresistance. Surface engineering technology can be used to improve the surface properties ofthe aluminum alloys. TIG cladding is the technology adding deposited materials to thesurface of the base to obtain the desired special properties. In this paper, with pre-coatpowder and synchronous powder feeding method, the surface of aluminum was claddedwith Fe and Ni powders. the surface layer of metallurgical bond with the matrix wasprepared by changing the process parameters such as the arc current and the arc travellingspeed. This paper mainly studied the effect of process parameters on the microscopicmicrostructure of the cladding layer.When TIG cladding Fe and Ni powders，with the arc current increasing，the thicknessof the obtained cladding layer was increasing; so was the width. With the increase of thetravelling speed，the cladding layer thickness obtained gradually decreased，and the widthwas narrowed. When the matrix was TIG cladded with Fe and Ni powders，cladding layerscontaining hypoeutectic，eutectic and hypereutectic microstructure could be obtained bychanging the arc current or the arc travelling speed. The hypoeutectic microstructure wascomposed of α-Al phase and eutectic FeAl3+α-Al or NiAl3+α-Al; the eutecticmicrostructure was composed of FeAl3+α-Al or NiAl3+α-Al; and the hypereutecticmicrostructure was composed of primary crystal phase FeAl3or NiAl3phase and FeAl3+α-Al or NiAl3+α-Al. When the cladding layer is hypereutectic, the obtained FeAl3phaseobtained mainly characterized by thick strips，needles，and flower shape. The NiAl3phasewas mainly strips and grainy.With Fe and Ni melting into the matrix，the micro hardness and relative wearresistance of the aluminum surface layer was greatly improved. When pre-depositing Fepowder，with the increase of the arc current，the values of microhardness increased at firstand then decreased; the maximum micro-hardness value was477.8HV while the arc currentreached200A. The relative wear resistance of the cladding layer first increased and then decreased, the maximum value of relative wear resistance was3.0; while the frictioncoefficient first decreased and then increased.When the Fe powder was added，with the increase of the arc current，the surfacehardness of the cladding layer decreased，the relative relative wear resistance was graduallyreduced, while the coefficient of friction increased，the maximum micro-hardness value was123.8HV. the maximum value of the relative wear resistance was1.57; With the increase ofthe arc travelling speed，the micro-hardness of the cladding layer and the relative relativewear resistance decreased first and the reduced; While the friction coefficient increased.When the Ni powder was added，with the increase of the arc current，the surfacehardness of the cladding layer decreased gradually，the relative relative wear resistancegradually decreased, while the coefficient of friction increased, the maximummicro-hardness value was137HV. With the increase of the arc travelling speed，the relativerelative wear resistance increased first and then reduced; The friction coefficient decreasedfirst and then increased; the maximum value of the cladding layer’s micro-hardness was230HV. The maximum value of the relative wear resistance was1.47, improvedmicrohardness and wear resistance of the substrate.