Multi-physics Coupled Numerical Simulation Of Laser Cladding Based On Iron-based Composites

With the development of modern industrial technology,laser cladding technology has been widely used in various processing fields.However,the physical and chemical reactions involved in the laser cladding process are very complicated,and it is difficult for the existing technology to detect the real-time physical fields during the processing.The development of computer simulation technology has effectively solved this problem.The computer simulation technology is used to simulate the cladding process.The research results can provide theoretical guidance for specific experimental processes.Therefore,it is of great significance to carry out the calculation and simulation of the laser cladding process.In this paper,COMSOL Multi-physics software is used to study the laser cladding process of iron-based cladding layer.The temperature field model,thermal-fluid coupling model and thermal-stress coupling model in the laser cladding process are established and systematically studied The influence of process parameters such as laser power,defocus amount,scanning speed,overlap rate,and scanning mode on the temperature field of the molten pool is analyzed.The process parameters and the surface tension coefficient of the material during the multilayer cladding process are analyzed.The influence of the stress field during the cladding process was explored,and the relationship between the thermal expansion coefficient of the material and the stress field was analyzed.The following conclusions were obtained:(1)With the increase of laser power,the temperature peak in the center of the molten pool increases,the high temperature area at the edge of the molten pool expands,and the depth and width of the molten pool increase.As the laser spot diameter increases,the temperature of the center of the molten pool decreases,and the depth and width of the molten pool decrease.As the scanning speed decreases,the temperature of the center of the molten pool increases,and the depth and width of the molten pool increases.(2)Compared with single-direction scanning,the reciprocating scanning method has a lower temperature gradient after cladding because the heating process is continuous.With the increase of the overlap rate,the secondary heating temperature of the coating at adjacent locations increases,but it has little effect on the peak temperature of each coating when cladding.(3)Increasing the laser power,reducing the spot size and reducing the scanning speed will increase the peak value of the fluid flow velocity inside the molten pool.The powder feeding rate has no effect on the temperature field and flow field in the molten pool,but it willincrease the height of the cladding layer.(4)The flow direction of the liquid fluid inside the molten pool is affected by the surface tension coefficient of the material.When the material surface tension coefficient is negative,the internal fluid of the molten pool flows from the center of the molten pool to the edge of the molten pool.When the surface tension coefficient is positive,the fluid inside the molten pool flows from the edge to the center of the molten pool.Negative surface tension coefficient material can obtain shallow and wide molten pool,while positive surface tension coefficient makes the profile of the molten pool deep and narrow.With a surface tension coefficient of the same absolute value,the speed peak at a positive surface tension coefficient is greater than a negative surface force coefficient.The greater the fluid velocity in the molten pool,the more uneven the surface of the cladding coating.For materials with a large surface tension coefficient and a positive value,it is not easy to obtain a cladding coating with a flat surface.(5)In the initial stage of laser cladding,the thermal stress increases as the distance from the center of the laser beam increases.When the thermal stress value exceeds the material yield limit,the material yields,a low stress area appears in the center of the molten pool,and the maximum stress is distributed at the edge of the molten pool.In the later stage of laser cladding,the residual stress after cladding is mainly distributed at the interface between the coating and the substrate,and this area is a sensitive area where cracking occurs.The peak value of residual stress after laser cladding is simultaneously affected by the thermal expansion coefficients of the coating and the substrate.The larger the difference between the two,the greater the residual stress of the cladding layer.