Research On Interface Characteristics And Properties Of Fe-based Amorphous Coating On Magnesium Alloy

Magnesium alloy is a kind of light metal material.Good cutting performance,high specific strength and specific rigidity makes this lightweight material widely used in aerospace and automotive manufacturing,but its poor wear resistance makes it difficult to use in harsh environments,which limits its application.The Fe-based amorphous coatings have low preparation costs and excellent wear resistance.Therefore,this paper is aimed to improve the wear resistance of magnesium alloy components by coating Fe-based amorphous coatings on magnesium alloy.In this paper,the supersonic flame spraying(HVOF)technology is used to prepare the Fe-based amorphous coatings on the surface of the magnesium alloy by adding an intermediate layer.In this paper,the Fe-based amorphous coatings were prepared on the surface of magnesium alloy by adding a intermediate layer through HVOF technology.The spraying powder were amorphous powders made of industrial raw materials.The microstructure of the coatings were observed and analyzed by DSC,SEM,XRD,Vickers microhardness tester and friction and wear tester.The bonding strength between Fe-based amorphous coatings and magnesium alloy substrate was tested,and the effects of different process parameters and friction and wear environment on the wear resistance of the coating were studied.The conclusions are as follows:The Fe-based amorphous coatings are difficult to be directly prepared on the surface of magnesium alloy by HVOF.There are a lot of defects at the bonding interface which make the coatings easy to peel off.The coatings can be effectively prepared on the surface of magnesium alloy and without obvious defects by adding intermediate layer.The amorphous content and porosity of the coatings decreases with the increase of kerosene and oxygen flow under the same spraying conditions,and the highest microhardness can reach 951 HV_0.2,which is much higher than that of the magnesium alloy substrate.The porosity and amorphous content of the coating decreases when the preheating temperature of substrate increases before spraying.The better the fluidity of the sprayed powder,the more obvious the oxidation phenomenon in the coating.With the increase of spray gun size,the density of the coating increases.There is element diffusion phenomenon at the bonding interface of coatings after adding intermediate layer,and the main combination mode is metallurgical combination.Increasing the thickness of magnesium alloy substrate can reduce the effect of thermal deformation on bonding and effectively improve the bonding strength of the coatings.The flow rate of oxygen and kerosene has an important effect on the bonding strength of the coatings,which can reach 54.79 MPa at most.Ni-coated WC and Co-coated WC reinforced phase particles were added to the coating to improve the wear resistance of the coatings.The layer of coatings with Ni and Co elements plays a good transition role at the interface between the coatings and the WC particles,which makes the strengthening phase particles and coating can be effectively combined.The average friction coefficient of the Fe-based amorphous coatings prepared on the surface of the magnesium alloy is only 0.097,which is much lower than the 0.23 of the WE43.The density of the coatings has an important effect on the wear resistance of the coatings.The defects in the coatings are easily led the worn surface to get damage,so the average friction coefficient will increase when the density of the coatings get down.During to the high hardness of the reinforced phase particles,the friction coefficient of the composite coatings is higher than that of the Fe-based amorphous coatings under low load.When the load increases to 20 N,the reinforcing phase particles play an anchoring role in the composite coatings,and the friction coefficient is lower than that of the Fe-based amorphous coatings.