Theoretical Analysis And Experimental Research On Laser Cladding Thin-Wall Parts

Laser cladding technology gets rid of the limitation of moulds and tools.It only needs to import the 3D data file into the control system of the equipment,and use the laser and powder conveying system to pile up the material layer by layer,then it can make the compact metal parts.Because it can shorten the manufacturing cycle,simplify the manufacturing process of processing thin-walled parts,and save materials,it is widely used in the direct forming manufacturing and repair of difficult-to-machine metals and complex shaped thin-walled parts.During the process of laser cladding and forming thin-walled parts,the process parameters and the temperature of the molten pool seriously affect the size and performance of the thin-walled parts.In this paper,Fe313 powder is used as the cladding material,and 45 steel is used as the base material.The negative feedback effect and temperature adjustment strategy in the forming process of thin-walled parts are studied.The forming experiments of inclined and ring thin-walled parts are carried out to analyze the forming quality.The main research contents of this paper are as follows:(1)The mathematical model of laser cladding is established,and the distribution density of powder is modeled by Gaussian distribution.The height of cladding layer under different defocusing amount of powder is predicted and verified by experiments.The mathematical model of the forming process of thin-walled parts is established,and the negative feedback effect in the forming process of thin-walled parts is studied.The paper takes the forming efficiency and negative feedback effect as the evaluation criteria to analyze the selection of the defocusing amount of powder and the lifting amount of Z-axis in the forming process of thin-walled parts.(2)The temperature of molten pool is very important to the forming quality of thinwalled parts.The temperature evolution of molten pool in the forming process of thinwalled parts is studied by numerical simulation.This paper analyzes the temperature evolution of the molten pool in the direction of cladding height and scanning direction during the forming process of thin-walled parts,compares the effect of different ways on the temperature adjustment of the molten pool,optimizes the temperature adjustment strategy,and analyzes the influence of the temperature adjustment of the molten pool on the size accuracy,microstructure and microhardness of the thin-walled parts.(3)This paper establishes a mathematical model for the forming of inclined thinwalled parts,and analyzes the limit inclination and forming quality of three forming methods.In this paper,the vertical offset method is used to form the inclined thin-walled parts,and the forming accuracy of the thin-walled parts is analyzed,the metallographic structure and microhardness of the dorsal,middle,and abdominal regions of inclined thinwalled parts are analyzed,and the influence of the offset on the hardness of the inclined thin-walled parts is studied.By optimizing the process parameters,forming experiments are carried out to analyze the forming quality of the twisted thin-walled parts with continuous inclination.(4)Taking ring-shaped thin-walled parts as an example,the influence of negative defocusing,scanning path and equipment start-stop on the quality of cladding is studied.By comparing the error band between the measured value and the mean value,the influence of the negative defocusing of the powder and the scanning path on the flatness of the top of the coating during the cladding process is analyzed.By comparing the metallographic structure and microhardness at the starting point of the ring-shaped thin-walled parts of different scanning paths,the paper analyzes the influence of the start-stop of the equipment on the quality of the cladding.