The Microstructures And Properties Of Al-Fe-Mn And Al-Fe-Nb Layers By Argon Arc Cladding On Aluminium Substrate

The aluminum and aluminum alloy have the excellent performances of high specific strength,excellent electrical conductivity and thermal conductivity,but the abrasion usually occurs due to the poor shortcomings of low hardness and relative wear resistance.TIG cladding is a kind of surface strengthening technology adding the reinforced material to the surface of the basis material,which can obtain the surface layers of desired special properties by changing component content and microstructures of the surface of the basis material.In this paper,ternary argon arc cladding layers of Al-Fe-Mn and Al-Fe-Nb are successfully prepared by pre-coat powder method using Al,Fe,Mn and Nb as pre-coat materials based on binary system.The microstructures and properties of the cladding layers are studied by changing the arc current（100 A-200 A）and the ratio of the mixed powders.The arc heat directly acts on the pre-coat alloy powders by pre-coat method when preparing the cladding layer,and the powders melt and the heat is conducted to the aluminum matrix so as to partially melt the molten pool.The molten alloy powders enters the molten aluminum bath,which cause the alloy elements to interact with aluminum and form the corresponding intermetallic compounds in the process of a liquid diffusion and dissolution process.The cladding layers generally have an area of uniform composition and microstructure distribution in the upper middle part,and there is a transition region with less alloy elements below the cladding layer due to the faster heating and cooling speed of the argon arc cladding method.Partially molten and insufficiently dissolved alloy powders also coalesce together to form agglomerate zones dominated by the composition of the alloy powder.Occasionally,defects such as pores may occur in the cladding layer.In order to promoting the melting of the alloy powders and reduce the defects of the cladding layers,a method of pre-coating the aluminum powder with the alloy powder is adopted to promote the wetting,dissolution and diffusion processes of the alloy powder and the aluminum fusibility.The microstructures of the cladding layers of argon arc cladding Al-Fe-Mn on pure aluminum substrate show that the phase composition of the cladding layer mainly includesα-Al solid solution and FeAl₃ compound when pre-coating Al+Fe powders.When the arc current is small,FeAl₃ compound is strip and block.In the case of a large arc current,the content ofα-Al solid solution increasesand star-shaped FeAl₃ compounds appear in the cladding layer.When synchronously feeding Fe power,the Fe-Al compounds are less.When the arc current is small,the FeAl₃ compound is mainly elongated with a small amount of star shape.With the increase of arc current,the content ofα-Al solid solution increased and the long strip of FeAl₃ compound decreased with increase of the star-shaped FeAl₃ compound.The phase composition of the clad layer of pre-coating Al+Mn powders mainly includesα-Al solid solution and Al₁₁Mn₄ compound.When the arc current is small,there are more agglomerates with pores and crack defects in the cladding layer,and strip-shaped Al₁₁Mn₄compound with uneven distribution.With the increase of arc current,the content ofα-Al solid solution in the cladding layer increases,and the Al₁₁Mn₄ compound is a leaf-like structure composed of black particles.The density decrease and the pore and crack defects disappeare.The phase composition of the cladding layer obtained by pre-coating Al+Fe+Mn powders is mainlyα-Al solid solution,FeAl₃ distributed in a clastic manner and the black granular Al₁₁Mn₄ compounds distributed dispersedly.With the increase of arc current,the content ofα-Al solid solution increases,and the FeAl₃ and Al₁₁Mn₄ compounds decreases.The properties of the cladding layer mainly depend on the relative content of the compound in the cladding layer.With the increase of the arc current,the heat input increases and the melting amount of the aluminum matrix increases,which leads to a relative decrease of the content of the compound in the cladding layer,and leads to a gradual decrease of the average microhardness of the cladding layer and a gradual deterioration of the wear resistance.With the increase of argon arc current,the mean value of microhardness of cladding layer by pre-coating Al+Fe powders gradually decreases from 170 HV to 55 HV and relative wear resistance gradually decreases from 2.54 to 1.23.When synchronously feeding Fe power,the maximum microhardness of the cladding layer was only 40 HV and the relative wear resistance was 1.39 due to the relatively few Al-Fe compounds.With the addition of Al+Mn and Al+Fe+Mn powder,with the increase of the arc current,the mean value of the microhardness of the Al+Mn cladding layer decreased from 186 HV to 85 HV,and the relative wear resistance decreased from 3.12 to 1.21.The mean value of microhardness of the Al+Fe+Mn cladding layer decreased from 138 HV to 107 HV,and the relative wear resistance decreased from 2.61 to 1.39.In the series of Al+Fe+Mn cladding layer,the best wear resistance is the Al+Mn binary system cladding layer and the relative wear resistance is3.12.The microstructures of the cladding layers of argon arc cladding Al-Fe-Nb on pure aluminum substrate show that the phase composition of the cladding layer of pre-coating Al+Nb powders is mainly includesα-Al solid solution,dendritic and granular Nb Al₃compounds and a small amount of Nb agglomerates.With the increases of arc current and input of heat,the melting amount of aluminum matrix increases and the dilution rate increases,which lead to increase ofα-Al solid solution and the gradual decrease of Nb agglomerates and NbAl₃ compound.When its arc current is changed in pre-coating Al+Fe+Nb powders,the phase composition of the cladding layer mainly includesα-Al solid solution,FeAl₃ and NbAl₃ compounds.When the arc current is 120 A,the heat input is small,the aluminum matrix melts less and the compound is denser with crack defects.With increase of arc current,the content ofα-Al solid solution increased and crack defects disappeared,FeAl₃ compounds were mainly elongated and NbAl₃ compounds were mainly dendritic and granular.When changing its compositions（weight ratio of Nb to Fe）in pre-coating Al+Fe+Nb powders,the phase composition of the cladding layer includesα-Al solid solution,FeAl₃ and NbAl₃ compounds.With the increase of content of Fe in the pre-coated powders,α-Al solid solution increased,dendritic and granular NbAl₃ compounds gradually decreased and elongated FeAl₃ compounds gradually increased.When Al+Nb powder are pre-coated,the increase of arc current resulted in the decrease of Al-Nb compound,the mean value of the microhardness of cladding layer decreased from110 HV to 79 HV,and the relative wear resistance decreased from 3.26 to 1.47.When its arc currents is increased by pre-coating Al+Fe+Nb powders,the mean value of the microhardness of the cladding layer decreased from 302 HV to 110 HV,and the relative wear resistance decreased from 3.74 to 1.30.When changing its compositions by pre-coating Al+Fe+Nb powders,with the increase of Fe in pre-coated powders,Al solid solution in cladding layer increased,compound decreased,the mean value of microhardness dropped from 144 to 103 HV,the relative wear resistance decreased to 1.80 from 3.14.The wear resistance of Al-Fe-Nb argon arc cladding is the best,and the relative wear resistance is as high as 3.74.In the cladding layer of the binary system of Al-Mn,the wear resistance is the best.The relative wear resistance is 3.12 when the mass ratio of aluminum powder to manganese powder is 1:3 and the argon arc current is 120 A.The Al-Fe-Nb cladding layer has the best wear resistance and the relative wear resistance is 3.74 when pre-coating Al+Fe+Nb powders and arc current is 120 A and Al:Fe:Nb=1:4:6（mass ratio）in the ternary cladding layer.