Basic Experiment And Simulation On Laser Cladding Forming Of Metal Powder

Without any die,laser cladding forming can produce any complex shape parts with a variety of materials,shorten the manufacturing cycle of products,reduce production costs and enhance competitiveness of products,in particular,it will help the production of parts with complex shape,multi-variety,low-volume.Laser cladding forming of metal powder needs no external force,the laser beam energy has good controllability,it reduces the lack of existing methods such as the complexity of process and so on,however,the quality of cladding layer is instable,so there is still a gap from the actual application,it needs further researching, according to the basic principle of laser cladding,the control of process,quality and temperature for cladding forming,the paper work done and the results obtained are as follows:(1) The theoretical analysis on laser cladding process is done.The interaction between metal materials and laser in cladding process,the conduction of energy in metal powder, melting forming process of metal powder and surface topography of laser cladding are analysed,the awareness to process of laser cladding forming is deepened;by reasonable simplified heat conduction equation and boundary conditions extreme power density of melting and vaporization for laser cladding are calculated,which are 1.31×10~3W/mm~2 and 3.98×10~3W/mm~2.(2) The experiment of laser cladding forming Ni60 alloy powder is done by using JK701 Nd:YAG pulse solid laser.The scopes of process parameters are determined.The effect of different laser parameters on single-layer cladding geometrical dimension is studied through single-factor experiment.The scopes of process parameters are optimized,and then a set of optimal process parameters are obtained through orthogonal experiment:laser power 80W, scanning speed 100mm/min,defocusing amount 8mm,pulse width 3ms,frequency rate 25Hz, the multi-layer cladding experiment is done by using optimal process parameters and reasonable lap factor,the final pieces are formed.(3) Considering the width,height and surface quality of cladding layer in the experiment of laser cladding Ni60 alloy powder,the single-layer and multi-layer cladding pieces in optimal process parameters are considered as detected pieces,and the quality of cladding layer is comprehensively detected and analysed(including surface topography,metallographic testing,XRD testing,hardness testing),the results show microstructure of cladding layer is dense,the strength and hardness satisfy requirements.(4) The three-dimensional temperature field model of laser cladding forming Ni60 alloy powder is established and simulation is done.The results of simulation show real-time temperature changes of forming process,laser cladding is the process of rapid melting and rapid solidification,Ni60 cladding layer is metallurgically bonded with substrate,the calculation results of finite element are more in line with measurement results of experiment, which provide theoretical and technological supports.The work in this paper supplies theoretical and experimental foundation for application of laser cladding rapid forming,and this paper presents the choice methods of laser process parameters and important criterion of reasonableness for laser energy density during cladding process,h/H should not exceed 1,that is,the remelted depth of cladding layer should not exceed the height of cladding layer,which have a certain guiding significance to the practical application of laser cladding forming.