Study On The Mechanism And Diffusion Behavior Of Laser Cladding Considered The Interaction Of Laser And Powder

Laser cladding is an advanced green additive manufacturing technology,which is often used for surface strengthening and surface repair of parts.It has the advantages of small thermal deformation,a high degree of bonding,a high degree of automation,and good quality of the cladding layer.It has wide applications in aerospace,automobile and ship,biomedicine,energy and chemical industry and other fields.However,the current laser cladding technology has not been fully developed.There are low utilization of cladding powder,slow cladding speed,and the presence of pores,inclusions,cracks and other microstructure defects in the cladding layer.Numerical simulation and experimental research on the laser cladding process can provide theoretical guidance for actual production and have important significance for the development of laser cladding technology.In this paper,a three-beam coaxial laser cladding process multi-physics numerical model was established.The laser cladding process parameters were analyzed from multiple angles.The interaction mechanism of laser and powder and the transient law of the multi-field coupling for the molten pool in the laser cladding process were revealed.The main research contents and conclusions are as follows:(1)A numerical model of interaction of laser and powder was established.The effect of temperature change on material physical parameters was considered.The temperature rises process of powder particles in the laser beam calculated and analyzed.Based on the response surface method,the influence of different process parameters on the temperature rise speed of a single powder particle in the laser beam is analyzed.Further,the influence of process parameters on the temperature distribution of powder flow in the laser beam was revealed.(2)Based on the finite volume method,a powder ejection behavior flow field model was established.Based on the constructed three-beam coaxial cladding head geometry model,the three-beam coaxial powder flow field was numerically calculated,and the influence of process parameters on powder utilization was revealed.The best process parameters were determined by orthogonal experiments,and the powder utilization rate was calculated.An initial condition for subsequent calculations provided.(3)Considering the interaction effect of laser and powder,a thermo-solid-flow multi-field coupling model of the temperature field,stress field and molten pool flow field in the laser cladding process was established.The temperature field,stress field and molten pool flow field distribution under different laser powers were compared and analyzed,and the changing laws of different physical fields with laser power were revealed.(4)A mass transfer model for the laser cladding process was established,and the mass transfer behavior of laser cladding was revealed.The distribution of various elements in the cladding layer was quantitatively determined,and a theoretical foundation for improving the quality of the cladding layer in production was laid.(5)Material science experiment analyses were conducted,including SEM,EDS,XRD,friction and wear,and hardness experiments.The theoretical results are compared with the microscopic characterization experiments of the cladding layer to verify the validity of the model.The macro-mechanical properties and microstructure morphology of the cladding layer were obtained through experiments.