Key Technology On Calculation Model And Experimental Research Of Laser Cladding Process

As a kind of additive manufacturing technology,laser cladding is widely used in component repair and remanufacturing in various fields.The shape of actual components usually contains non planar surfaces such as cylinders.In addition,during the processing of multi-track and multi-layer cladding,the superposition between tracks makes the surface of the workpiece rough.Therefore,in order to broaden the application of laser cladding technology and carry out laser cladding on the uneven surface of parts,this paper studies the laser cladding technology on planar and non-planar substrate in the theory,experiment and process model.Aiming at solving the problems of profile evolution,temperature distribution and forming quality of the cladding layer on the planar and non-planar substrate,the thermal effect and the variations of interfacial free energy and gravitational potential energy of molten pool during laser cladding are studied in this paper.For the problem that the rapid variation of the temperature of the molten pool in the process of the laser cladding will lead to the poor quality of the cladding layer,the ultrasonic vibration-assisted laser cladding process is deeply studied in this paper,and the laser cladding process model of metal alloy is established.Based on the action mechanism of laser-powder and the droplet forming method,the profile calculation model of the cladding layer is developed by using cellular automata method.The model considers the influence of material thermophysical parameters,establishes the relationship between laser power,scanning speed,powder feeding rate and cladding layer profile parameters,and describes the profile of single and multiple cladding layers of different materials under different process parameters.In order to verify the applicability and accuracy of the model for the simulation of the profile of the cladding layer,single track experiments under different process parameters were carried out on three alloy powders Stellite6,Ni60 AA and SUS316 with different thermophysical parameters.In addition,the step experiment method is used for multi-track cladding with different overlap,so as to obtain the profile parameters of different numbers of tracks in an experiment,which saves the experimental material and time.Experiments show that the model has high accuracy and can predict the profile of the cladding layer for different materials on horizontal substrate under different process parameters.In this paper,aiming at calculating the profile of the cladding layer on the inclined substrate,the laser heat source model and the powder beam model are established.The shielding effect of the powder on the laser and the reflection effect of the inclined substrate on the laser are considered in the model,and the rebound effect of the substrate on the powder is considered in the model.Then,from the point of view of force in the forming process of the cladding layer,the final profile of the cladding layer is calculated by droplet forming method,and the model of cladding layer profile is developed by cellular automata method.The model considers the influence of material thermophysical parameters,studies the profile of cladding layer under different powder feeding rates,and describes the profile of cladding layer on substrates with different inclined angles.Then,single track experiments were carried out on alloy powders Stellite6 and Ni60 AA respectively.The calculated results of cladding layer profile on substrates with different inclined angles are basically consistent with the experimental results.In this paper,the cladding profiles on cylindrical substrates with different diameters are calculated.In the process of coaxial powder feeding laser cladding,the powder distribution and laser heat source energy distribution are considered.The mechanism of laser cladding,including powder feeding process and thermal effect,is analyzed.At the same time,the influencing factors of energy loss in the process of laser cladding are analyzed.Then,from the point of view of the balance of gravitational potential energy and interfacial free energy of molten metal,the droplet forming method is improved,and the profile of the cladding track on cylindrical substrate is calculated.Then,according to the laser cladding process,the calculation models of cladding track profile and temperature field are established by using cellular automata method.Finally,the accuracy of the model is verified by experiments on flat plates and cylindrical substrates with different diameters.It is proved that the model is feasible to predict the temperature field and profile on substrates with different shapes.This paper lays a foundation for the research of surface repair and provides a reference for the selection of process parameters in practical machining.In order to improve the performance and spreading area of cladding layer,ultrasonic vibration-assisted laser cladding technology was studied in this study.According to the ultrasonic vibration-assisted laser cladding process,the calculation model of cladding layer profile and temperature field is established by using cellular automata method.The powder distribution and laser energy distribution of four-way powder feeding nozzles are studied by the model.The model considers the influence of ultrasonic vibration on the profile and temperature field of cladding layer,establishes the ultrasonic vibration energy sub model,adds the energy transmitted from ultrasonic vibration to molten droplets to the droplet forming method,and improves the energy equation of the droplet forming method,so that the model is suitable for the calculation of cladding layer profile and temperature field under ultrasonic vibration.Then,the Stellite6 powder was experimentally studied to verify the accuracy of the model in calculating the profile and temperature field of the cladding layer.In addition,the microstructure and microhardness of the cladding layer were analyzed to explore the effect of ultrasonic vibration on the mechanical properties of the cladding layer.Experiments show that the model can accurately calculate the profile and temperature field of the cladding layer,and it also proves that ultrasonic vibration-assisted laser cladding is helpful to improve the mechanical properties of the cladding layer.In this paper,the profile and temperature field models of the cladding layer on horizontal and non-horizontal substrates are established,and ultrasonic vibration-assisted laser cladding technology is studied,which lays a foundation for the prediction of the overall profile of the workpiece,and has high theoretical significance and practical engineering application prospect.