Simulation Of Temperature Field And Experimental Study Of 3D Laser Cladding Fe-based Alloy

3D printing is a new development of additive manufacturing,and the use of 3D printing process forming metal components is an important development direction of mechanical manufacturing industry.Laser cladding and forming technology is a new rapid prototyping technology based on laser processing technology.The cladding technology based on high energy laser beam can not only be used for the surface modification of the base material,but also can be used for the repair of the worn parts and the forming of the metal components.The technology of surface modification of material by laser is a very complicated process.In this paper,the optimal process parameters are predicted by the dynamic simulation of temperature field in laser cladding process.The simulation results are verified by the double factor comprehensive test method,and the friction and wear tests of the cladding layer with the optimal process parameters and the overlap rate are carried out.The main research contents are as follows:(1)The three-dimensional temperature field model of laser cladding low carbon Fe-based alloy on Q235 steel surface is established,taking into account the factors such as convection,thermal physical parameters,latent heat of phase change and synchronous powder feeding.The temperature change curves of the top and bottom points of cladding layer are analyzed,and the forming quality of cladding layer is predicted.The results show that when P=2000 W and v=10 mm/s,the maximum temperature of the top and bottom points of the cladding layer is 2300 ℃ and 1500 ℃,respectively;besides,the cladding layer with good surface morphology,good metallurgical bonding with the substrate and low dilution rate may be prepared.Through the analysis of the temperature distribution at different time points,we can see that in addition to the initial stage of the cladding,the temperature field of the molten pool is stable,and the maximum temperature of the molten pool is located between the center of the spot and the deepest point of the weld pool.(2)Experimental study of laser clad Fe-based alloy is carried out on 3D printing and laser remanufacturing platform.The laser power and scanning speed were taken as variables,and the geometrical shape,macroscopic morphology and microstructure of the cladding layer are tested and analyzed under different process parameters.The results show that the width of cladding layer increases with the increase of laser power,while the thickness of cladding layer presents double peaks shape with the increase of laser power;the width and thickness of the cladding layer decrease with the increase of scanning speed.The energy density of laser line is presented to illustrate the matching of laser power and scanning speed,which is important for judging the continuity and over burning of the surface of the cladding layer.The simulation of temperature curves and metallographic images show that the cladding layer is composed of a plane crystal and a dendrite which is perpendicular to the interface,and the transition zone is a lath martensite with Gr and Ni;The microstructure of clad zone is uniform and compact,the matrix and cladding materials are well bonded and the dilution rate is low,the ferrite and pearlite in the heat affected zone are refined,and the cladding layer is of excellent quality.(3)Multiple-track coatings of Fe-based alloy are prepared under single channel optimum process parameters and appropriate overlapping ratio,and then are processed into test ring with different grinding depth.The friction and wear tests are done on the MVF-1A friction and wear tester under the conditions such as uniform velocity and variable load,and constant load and varying velocity.The results show that the friction coefficient increases with the increase of the load,and decreases slightly with the increase of the rotational speed.By measuring the microhardness of the cladding layer at different depths,it is known that there are the three stages of slow decline,accelerated decline,slow descent with the increase of the distance to the surface,and the hardness(350 HV)of cladding zone is the highest and is about twice that of the substrate.Wear SEM pictures show that with the increase of load,the adhesion wear is increased,the wear mechanism of clad zone is abrasive wear and adhesive wear,and that of transition zone is delamination wear,adhesive wear and abrasive wear.