Numerical Simulation And Experimental Investigation On Laser Micro-melting Nano-SiC Particles Reinforced Al-based Composite Coating

In mechanical industry,aluminum(Al)is one of the most consumable metals,which is second only to the steel.The failure of most Al metal components usually occurs on the surface.Therefore,the surface property of Al components is the key factor which determines the overall performances in application.In addition,the nano-particles reinforced metal matrix composite coatings have many advantages,such as good plasticity,good toughness,high hardness and high temperature resistance,which shows a wide range of engineering applications.While the nano-particles will be melted during the laser cladding,leading to the decrease of strengthening effect of nano-particles.In order to solve the problem,the method of laser micro-melting has been put forward to prepare nano-particles reinforced metal matrix composite layer in this paper.The finite element analysis softwares,such as ANSYS and FLUENT,have been used to simulate the temperature field,flow field and the microscopic dynamic process of the nano-particles in the process of laser micro-melting nano-SiC particles on the surface of commercial pure aluminum(CP Al).The related experiments have been completed,and the main research results are as follows:(1)The temperature fields of the laser micro-melting nano-SiC particles on the surface of CP Al have been simulated with different laser processing parameters.According to the results of temperature fields,the optimal laser parameters have been determined.The results show that the distribution of the temperature field is circular.Under the action of laser,and there was no similar phenomenon of tail support in continuous laser processing.The Al surface temperature presents the characteristics of urgent hot and cold quickly.With the increase of the single pulse laser energy and frequency,the maximum temperature and the size of molten pool are increased.The laser energy of 0.6 J,pulse duration of 10 ns,frequency of 1 Hz,spot diameter of 1 mm and scanning speed of 2 mm/s are selected as the laser parameters for the following simulation.(2)The flow field and the microscopic dynamic process of the nano-particles are studied during laser micro-melting.The results show that an inward rotating Marangoni vortex is generated at the fusion line of the weld pool after laser irradiation.Two symmetrical vortices are generated on the cross section of the weld pool.Two different sizes of vortices are generated in the radial direction of the weld pool.And the vortex at the center of the molten pool is stronger.The fluid on the surface flows from the center of the molten pool to all round.The visualization model of the dynamic process of high temperature nano-SiC particles with the Al substrate is created,and the reasonable mechanism is also described.The surface hardness increases with the increase of laser energy,which can be up to 163 HV at 0.6 J.(3)The experimental studies of the laser micro-melting nano-SiC particles on the surface of CP Al with different laser energy parameters have been carried out.The results show that the intensities of SiC diffraction peaks are enhanced with the increase of laser energies,which shows that the solid particles could be embedded into the Al substrate under the effect of laser micro-melting.With the increase of laser energies,the agglomeration of nano-particles is obviously reduced,and the nano-particles are distributed more uniformly in the Al substrate.