Preparation Of Aluminum Matrix Composite Coating Via Electrodeposition In AlCl₃-based Inorganic Molten Salts

Aluminum matrix composite coatings are aluminum or aluminum alloy coatings with the addition of reinforcement phase.The aluminum matrix composite coating not only has the advantages of corrosion resistance of the aluminum coating,but also has higher hardness and wear resistance,which is widely used in areas such as automobile and aerospace.At present,the aluminum matrix composite coating is mainly prepared via cold spraying,but in this way the particles in the coating are easy to agglomerate and the porosity is high.Analogous to the deposition of various metal matrix composite coatings via composite electrodeposition in aqueous solution,we attempt to prepare aluminum matrix composite coatings containing carbide particles via composite electrodeposition in aluminum chloride based inorganic molten salts.We firstly explored the preparation of Al/TiC（TiC average particle size:50 nm）composite coatings in Al Cl₃-Na Cl-KCl inorganic molten salts.Coherent and dense Al/Ti C coatings were prepared with a current density of 50 m A/cm² and magnetic stirring speed of 350 rpm using a bi-anode cell,and their hardness is obviously improved compared with that of pure Al coating.However,due to the low content and small contrast of Ti C particles in the coating,it is impossible to directly observe whether they are uniformly distributed in the coating.In order to further improve the content of carbide particles in the coating and make it easy to observe,WC particles with larger density and（relative to Al metal）larger contrast were selected.And three types of cell design,including a bi-anode arrangement with magnetic stirring,an asymmetrical electrode arrangement with mechanical stirring and a symmetrical electrode arrangement with mechanical stirring,were used for electrodeposition to explore the best design.The composite electrodeposition was performed with WC particle concentration of 20 g/L and current density of 50 m A/cm².The experimental results show that the WC particles in the Al/WC（WC average particle size:60 nm）coating prepared by mechanical stirring and symmetrical electrode arrangement are less agglomerated and more evenly dispersed.Based on the above research results,Al-Mn/WC（WC average particle size:400nm）composite coatings were prepared by the symmetrical electrode arrangement with mechanical stirring via composite electrodeposition in Al Cl₃-Na Cl-KCl-Mn Cl₂.The effects of stirring speed and current density on Al-Mn/WC composite coating were studied.The results show that with WC particle concentration of 20 g/L,current density of 55 m A/cm²,and stirring speed of 400～700 rpm,the WC particles in Al-Mn/WC composite coating obtained at 600 rpm have the most uniform distribution,and the hardness value of the coating can reach 640 HV_0.1.In addition,with the WC particle concentration of 30 g/L,the stirring speed of 700 rpm,and the current density of 15～75 m A/cm²,the WC particles in Al-Mn/WC composite coating obtained at 55m A/cm² have the most uniform distribution and the coating has the highest hardness(670 HV_0.1).