| In recent years,with the progress and rapid development of modern industry,nickel-based superalloy has been widely used in aerospace because of its high strength at high temperature and certain oxidation corrosion resistance and other comprehensive properties.However,components such as turbines,combustion chambers and blades are exposed to high temperature and harsh environment for a long time.Due to the limited hardness and wear resistance of pure high-temperature nickel-based alloy IN718,its performance is difficult to meet the requirements of the workpiece.Therefore,the use of cost-effective,machinability and non-pollution characteristics of particle reinforced metal matrix composites to prepare high-performance coatings for important parts for protective treatment or repair of parts failure shows great potential.In this paper,WC-12Co particles with good wettability of nickel were introduced into the nickel-based superalloy composite coating to make full use of the wear resistance,corrosion resistance,high temperature resistance and other properties of ceramic particles to improve the properties of nickel-based alloy IN718.In this study,numerical simulation,modeling and experimental testing were used to study the mechanism of laser melting pool,multi-channel lap bonding process,and the microstructure and properties of the composite coating.Finally,laser remelting was used to further improve the properties of the composite coating.The main research contents of this paper include:(1)Establish a laser molten pool model that considers molten pool flow,solidliquid phase transition and heat transfer through COMSOL,analyze the distribution of temperature field and flow field in the molten pool area,and explore the laser cladding And the influence of process parameters on the temperature field and flow field of the molten pool during remelting,compare the transition time,existence time and shape of the stable molten pool,and then analyze the influence of the process parameters on the solidification rate and temperature gradient.(2)Establish the mapping relationship between laser cladding process parameters and single-pass single-layer melting width and melting height by response surface method,and use parabola,cosine curve and circular arc curve to fit the contour curve of the cladding layer,and consider model accuracy and computational complexity determine the fitting function.On this basis,the oblique parabolic lap model is introduced into the multi-pass forming of laser cladding,and the optimal lap gap calculation model based on multiple process parameters is established.And verify the effectiveness of the model through experiments.(3)Through SEM,EDS,XRD,explore the influence of the percentage of the reinforcing phase on the microstructure,element composition and phase structure of the IN718/WC-12Co composite.The microhardness,friction and wear properties of the cladding layer of different compositions were tested and analyzed,and the influence of the percentage of the reinforcing phase on the processability of the IN718/WC-12Co composite was explored.The optimal ratio of WC-12Co is selected based on wear resistance and machinability for laser remelting treatment.(4)Laser remelting the selected ratio of IN718/WC-12Co composite coating,comparing the macro morphology and surface quality before and after remelting,and analyzing the improvement of defects such as poor lap,porosity,and peeling by remelting.Explore the influence of different laser energy density remelting on the microstructure of the cladding layer,and test and analyze the properties of microhardness,friction and wear. |
