Study On Thermodynamics,Stress Field And Temperature Field In Resistance Cladding Process

Iron-based amorphous alloy has the characteristics of high strength,high hardness,high wear resistance,corrosion resistance and low price.Its coating is widely used in aviation,aerospace,shipbuilding and other fields.Resistance cladding technology can overcome the defects such as pores and cracks in traditional coating preparation processes such as thermal spraying and laser cladding,and effectively prepare high-performance iron-based amorphous and amorphous/WC composite coatings.This paper mainly focuses on the research of resistance cladding technology,and explores the precipitation principle of precipitated phase Mo₂C in the process of preparing amorphous/WC composite coating through microstructure analysis and thermodynamic calculation.The distribution of stress,displacement and pore volume fraction of the powder layer during the powder pressing process was simulated by the finite element software COMSOL.The distribution of electric field and temperature field in the cladding process is simulated by finite element method.The simulation results show that the position of high temperature zone is consistent with the actual cladding process,and the dynamic change of temperature distribution is analyzed.Firstly,in the microscopic analysis of the amorphous/WC composite coating prepared by resistance cladding,it is found that the number and distribution of precipitates in the coating are closely related to the content and distribution position of WC-12Co.Through thermodynamic calculation,it is found that when the temperature is higher than 1510 K,WC has a tendency to spontaneously decompose into W₂C,and the stability of WC,W₂C and Mo₂C increases in turn.The precipitation of Mo₂C in the coating is due to the decomposition of WC particles into C and W₂C,which increases the content of free C element,and the combination of C and Mo elements forms Mo2C.Secondly,the powder pressing process was studied by finite element method.It was found that when the powder was pressed by the tablet press,the stress of the powder layer and the volume fraction of the hole were evenly distributed,only in a small range at both ends.During the pressing process,due to the change of the deformation state of the powder layer,the stress value of the powder layer increases first,then decreases and then increases with the specified displacement.The electrode wheel presses the powder,and the change law of the stress at the center of the powder layer with the specified displacement is similar to that of the tablet press.The stress changes on both sides of the region lag behind the center position in the specified displacement direction,and the lag degree increases with the increase of distance.Finally,the electric field and temperature field of the cladding process are studied by the finite element method.It is found that the area with high current density is:some points at the bottom of the powder layer directly below the electrode wheel,and the adjacent area centered on the left and right ends of the contact surface between the electrode wheel and the powder layer.The temperature field is centered directly below the electrode wheel and is distributed in a’concave’shape（initial stage）.It gradually changes to the distribution of high on the left,second on the right and low in the middle（transition stage）,and finally tends to be stable（equilibrium stage）.The cladding process was photographed by a high-speed camera,and it was found that there was a significant hysteresis in the high temperature region.The simulation results were consistent with the actual cladding process.