Wear And Corrosion Resistance Of Nano-TiN Particles Reinforced Aluminum-based Laser Cladding Coatings

Aluminum alloy materials have the characteristics of small density,high specific strength and good corrosion resistance,which are widely used in shipbuilding,automobile,aerospace and other industrial fields.Using laser melting technology to melt powder materials and form metallurgical bonding fusion layer on the surface of aluminum alloy substrate can further improve the wear resistance,corrosion resistance and mechanical properties of aluminum alloy substrate,and expand its application range.In this paper,AlSi10Mg powders are prepared by vacuum ball milling,nano TiN ceramic particles are prepared by evaporation condensation method,and AlSi10Mg/3wt.%TiN powders are prepared by feed technology of Metal injection Molding(MIM).AlSi10Mg and AlSi10Mg/3wt.%TiN coatings are prepared on the surface of 6061 aluminum alloy by laser cladding coating technology.The influences of laser power and scanning speed on the geometrical morphology of single channel cladding layer and the relationship between laser power and cladding layer surface spheroidization,porosity and microcracks are studied.Through microstructure observation and physical and chemical characterization,the microhardness,corrosion resistance and friction and wear properties of the two coatings are compared,and the strengthening mechanism of TiN ceramic particles reinforced powders are clarified.The research results of this paper are as follows:Firstly,AlSi10Mg powder and AlSi10Mg/3wt.%TiN composite powders have high sphericity,low surface roughness,moderate particle size and uniform element distribution.Nano-TiN particles are uniformly dispersed on the surface of AlSi10Mg particles.The prepared AlSi10Mg/3wt.%TiN composite powder has good laser absorption characteristics.Secondly,the influences of laser power and scanning speed on macroscopic morphology and microstructure defects of cladding layers are investigated.The change of laser power has obvious influence on the width and depth of the melted coating layer,but has little influence on the height of the melted coating layer.The increase of laser power within a certain range is beneficial to the improvement of pore defects,and the increase beyond this range leads to the aggravation of pore defects.Increasing the laser power can reduce the spheroidization of the melted layer surface and the grain size of the melted layer is gradually coarse.The change of scanning speed has obvious influence on the width and height of the coating,while the change of scanning speed is complex.Increasing the scanning speed can reduce the spheroidization of coating and crack defects,and refine the coating grains.Thirdly,the friction and wear properties of AlSi10Mg and AlSi10Mg/3wt.%TiN cladding coatings are investigated.The friction coefficient of AlSi10Mg and AlSi10Mg/3wt.%TiN cladding layer decreased by 22.1%and 29.4%,respectively,and the wear rate decreased by 34%and 49.6%,respectively.The metallurgical bonding between the two cladding layers and the substrate is good.The grain size of the fusion layer changes from coarse to fine,and from columnar crystal to equiaxed crystal.The middle and top of AlSi10Mg fusion layer is composed of spherical or fibrous eutectic Si,and the Al phase is divided into single cell equiaxed crystal.The main phases are ?(Al)phase,eutectic Si phase and a small amount of Mg2Si strengthening phase,and the Mg2Si strengthening phase improves the hardness of the cladding layer.TiN reinforced phase appears in the AlSi10Mg/3wt.%TiN cladding layer,and the microstructure is finer.With the liquid metal flow,TiN particles are uniformly distributed around the grain boundary,and a small amount of TiN particles are distributed in the grain,resulting in dispersion strengthening,which further improves the hardness of the fusion layer.Compared with the substrate,the test results show that the hardness of AlSi10Mg and AlSi10Mg/3wt.%TiN coatings increases by 22.5%and 33.1%,respectively.AlSi10Mg and AlSi10Mg/3wt.%TiN coatings bonded well with the substrate.The grain size of the coatings changed from coarse to fine,from columnar to equiaxed.The middle and top of AlSi10Mg cladding layer is composed of spherical or fibrous eutectic Si,and the Al phase is divided into single cell equiaxed crystal.The main phases are ?(Al)phase,eutectic Si phase and a small amount of Mg2Si strengthening phase,and the Mg2Si strengthening phase improves the hardness of the fusion aliasing layer.TiN reinforced phase appears in the AlSi10Mg/3wt.%TiN cladding layer,and the microstructure is finer.With the liquid metal flow,TiN particles are uniformly distributed around the grain boundary,and a small amount of TiN particles are distributed in the grain,resulting in dispersion strengthening,which further improves the hardness of the fusion layer.Compared with the substrate,the hardness of AlSi10Mg and AlSi10Mg/3wt.%TiN coatings increased by 22.5%and 33.1%respectively.The friction coefficient of AlSi10Mg and AlSi10Mg/3wt.%TiN fusion layer decreased by 22.1%and 29.4%,and the wear rate decreased by 34%and 49.6%respectively.Fourthly,the corrosion resistance of AlSi10Mg and AlSi10Mg/3wt.%TiN coatings is studied.Al-Fe-Si phase in 6061 substrate can promote corrosion and dissolution of surrounding matrix;the eutectic Si distributed around the Al grain in AlSi10Mg cladding layer can block the corrosion channel of anode Al phase and improve its corrosion performance.The microstructure of AlSi10Mg/3wt.%TiN coating layer is more refined,the segregation of eutectic Si is less,and the passivation film formed by the coating layer itself is more dense.TiN particles are uniformly distributed around the grain boundary,which can further hinder the electrolyte diffusion and reduce the channels and paths of corrosion.Therefore,the order of corrosion resistance from high to low is:AlSi10Mg/3wt.%TiN cladding coating>AlSi10Mg cladding coating>6061 substrate.