Experimental And Simulation Study On 304 Stainless Steel Powder Laser Cladding Assisted By Coupled Field Of Electric And Magnetic

Laser cladding technology has been widely studied and applied in the field of the material surface modification,due to the characteristics of the green environmental protection and excellent quality.It gradually becomes an indispensable part of the high-end manufacturing industry.Scholars have carried out a lot of research and experiments on the problems of the unstable properties and the uneven structure inside the cladding coating.The combination of external energy fields and laser cladding technology,such as alternating magnetic field assistance technology,can improve the deficiencies in laser cladding technology and effectively enhance the quality and properties of the cladding workpieces.However,the single magnetic field has a weak ability to regulate the molten pool,and the current assistance scheme is still not perfect.Therefore,in this paper,a kind of laser cladding method assisted by the coupled field of DC electric and alternating magnetic is proposed,in which a DC electric field is directly introduced into the cladding workpiece while an alternating magnetic field is applied around the cladding workpiece in the laser cladding process.Thereby,the DC electric field and the alternating magnetic field are superimposed on each other inside the molten pool.Through the coupled of multiple energy fields,the stirring effect inside the molten pool is strengthened.Thereby the convection distribution in the molten pool is enhanced,and the morphology and properties of the cladding coating are improved.In the experiments,the cladding powder is the 304 stainless steel and the cladding matrix is the 45 steel.Through designing and making the assistance platform of the electric and magnetic,the DC electric field and alternating magnetic field applied in the cladding workpiece can be controlled simultaneously.Then the changes of the morphology and physical properties of the cladding coating under different parameters of the alternating magnetic field and DC electric field are investigated.At the same time,an indirect coupled simulation scheme of Maxwell and Fluent is proposed,the effect of coupled field on the convection distribution of the molten pool in the laser cladding is explored though the finite element simulation method.First of all,the cross-section morphology and grain structure of the cladding coating assisted by the electric and magnetic coupled field are analyzed.The experimental results show that as the increase of the intensity of the alternating magnetic field in the coupled field,the height and width of the cladding coating decreases and the morphology becomes relatively flat under the condition of the laser power P=1500W,scanning speed v=4mm/s and spot diameter D=4mm.When the intensity of the alternating magnetic field reaches 60 mT and 80 mT,the grain structure in the middle of the cladding coating is obviously refined.It is also found that as the increase of the intensity of the DC electric field in the coupled field,the penetration of the cladding coating increases.When the intensity of the DC electric field reaches 6A and 8A,the area of the fine grain region on the surface of the cladding coating increases slightly.Then,the physical properties of the cladding coating assisted by the electric and magnetic coupled field are analyzed.The experimental results show that under the same laser parameters,as the increase of the intensity of the alternating magnetic field in the coupled field,the properties of the cladding coating is improved.For the cladding coating,the microhardness increases slightly,the friction coefficient decreases,the wear resistance increases,and the Cu-Ni compound appear in the phase composition.It is also found that the increase of the intensity of the DC electric field in the coupled field has a small effect on the properties of the cladding coating,but it has a great influence on the distribution of the Cu element in the phase composition.Furthermore,through the indirect finite element coupled simulation method of Maxwell and Fluent,the distribution of the electric field,magnetic field and electromagnetic force are analyzed.The effect of the electric and magnetic coupled field on convection distribution in molten pool is explored.The simulation results show that the electric field distribution in the coupled field is formed by the inductive current generated by the alternating magnetic field and the steady constant current generated by the DC electric field.The intensity of the magnetic field decreases along the magnetic inductance lines.It is also found that the value of the electromagnetic force increases gradually from the inter of the matrix to the upper and lower surface,and its directionand intensity are changed periodically over time.In addition,a number of stirring eddies appear inside the molten pool after adding the electric and magnetic coupled field,and the velocity curve of the molten pool appears a obvious fluctuation.In this paper,the effect of the electric and magnetic coupled field on the physical properties of the cladding coating are studied through the experiments and finite element simulation.The effect mechanism of the electric and magnetic coupled field on the flow of the molten pool is also explored.It provides a certain technical reference and guidance significance for common controlling the microstructure and morphology of the cladding coating by the coupled fields of the multiple external energy in laser cladding.