The Microstructure And Properties Of Fe-based Amorphous Composite Coatings Deposited By Electrospark Deposition

Amorphous alloys have excellent mechanical,physical and chemical properties because of their unique atomic arrangement,i.e.long-range disordered,short-range ordered atomic arrangement,and it is also known as metallic glass.Electro-spark deposition technology,which has the characteristics of high discharge frequency,small discharge area,concentrated energy,fast heating and cooling rate,is a preparation technology for amorphous coating with development potential.The preparation of amorphous coating using electric spark deposition technology can not only improve the surface properties of materials,but also broaden the application fields of amorphous alloys,and has broad application prospects.In this paper,the electrospark deposition technique and the method of pre-coating amorphous powder were used to prepare Fe-based amorphous composite coatings on the surface of 45Mn2 alloy with Fe-Cr-Ni solid solution and WC-10Co hard alloy as electrodes.The microstructure and properties of the deposited coatings were analyzed by optical microscope(OM),X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),microhardness tester,friction-abrasion testing machine and electrochemical workstation.The formation mechanism of amorphous structure during deposition processing was also studied by simulating the temperature field using ANSYS software.In the hardness test,the applied load is 100g and the loading time is 15s.In the friction-wear test,the wear ring is made of GCr15 steel with a rotating speed of 420r/min,a normal load of 40N and a wear time of 30min.In the corrosion test,the test temperature is 25?,the reference electrode is saturated calomel electrode,the platinum electrode is counter electrode,samples as working electrodes.The structure of the solid solution deposition coating is FCC structure,and the solid solution/amorphous composite coating is composed of amorphous structure and FCC solid solution.The coatings have metallic luster,the surface morphology is like orange peel.Sufficient diffusion occurs between sediment layer and matrix elements,which shows a good metallurgical combination between the coating and the base metal.The solid solution deposition coating has a surface roughness Ra of 0.734?m,an average thickness of 30?m,an average microhardness of 345HV,a wear amount of 0.04g,and a corrosion potential E_corr and a corrosion current density i_corr of-0.488V and 7.084?A/cm²,respectively.The solid solution/amorphous composite deposition coating has a surface roughness Ra of 1.969?m,an average thickness of 30?m,an average microhardness of 1091HV,a wear amount of 0.003g,and a self-corrosion potential E_corr and a corrosion current density i_corr of-0.486V and5.100?A/cm²,respectively.The WC deposition coating is mainly composed of W₂C and W₆C_2.54 phases.The WC/amorphous composite deposition coating is mainly composed of amorphous and W₂C phase.Morphology is similar to solid solution deposits.Moreover,good metallurgical bonding is formed between deposit and matrix metals.The WC deposition coating has a surface roughness Ra of 8.700?m,an average thickness of 30?m,an average microhardness of 1066HV,a wear amount of 0.008g,and a self-corrosion potential E_corr and a corrosion current density i_corr of-0.636V and 13.896?A/cm²,respectively.The WC/amorphous composite deposition coating has a surface roughness Ra of 4.313?m,an average thickness of 30?m,an average microhardness of 1345.9HV,a wear amount of 0.004g,and a self-corrosion potential E_corr and a corrosion current density i_corr of-0.543V and 8.792?A/cm²,respectively.The results of single impulse simulation experiment of electrospark deposition show that a large amount of energy is released instantaneously between the two electrodes in a gaussian distribution,and the heat affected region is on the scale of micron.The diffusion distance of heat along the depth direction is less than the radius direction,which indicates that the radius direction is more susceptible to the influence of heat.In the whole pulse cycle,The solid solution/amorphous composite coating and the WC/amorphous composite coating have the average cooling rate of the temperature field as the 10⁶?/s level,which can meet the requirement of cooling rate of amorphous alloy.