Research On New Method Of Laser Additive Manufacturing Based On Deep Penetration Welding Mode

Laser additive manufacturing is a new type of rapid prototyping technology,and wire feeding laser additive manufacturing is an important part.It has the advantages of high material utilization,low pollution and high economy.However,during the deposition and forming process,the wire will reflect the laser irradiated on it,which will reduce the utilization of laser energy and the deposition efficiency in the manufacturing process.Therefore,a new method of laser additive manufacturing based on deep penetration welding mode is presented in this paper,and a multi angle and coaxial protection deposition forming device is designed for this method.Experiments are carried out using this device,and we analyze the deposition of single pass cladding layer morphology and geometric features under different process parameters,and obtain the optimized process window.Furthermore,we analyze the relationship between the deposition efficiency and process parameters under the optimized process window conditions.Simultaneously,the transverse lap and longitudinal stacking test are carried out,and its structure and performance are analyzed.The results indicate that the coaxial deposition protection device possess good protection performance.The protective gas can pass through the nozzle firstly,and then through a certain length of laminar,finally entering the turbulent area,thus an effective protection of the molten pool formed.It is found that: optimizing angle between welding wire and the substrate normal is 5 degrees to 30 degrees,optimizing angle between laser beam and the normal substrate is 15 degrees to 45 degrees,optimizing defocus is 8mm ~ 10 mm,optimizing distance from laser beam position to the substrate is 2 mm ~ 3 mm.Based on the optimized test,the optimized process window of wire feeding high efficiency laser additive manufacturing is obtained by optimizing the parameters of wire feeding process.The melting width,height and depth of the cladding will be changed with the change of the process parameters.In the optimized process window,when the laser power is 3.0 kW to 4.5 kW,the cladding can adapt to larger scanning speed and wire feeding speed,which can increase the deposition efficiency.When the laser power is low,a well cladding layer can be obtained under lower scanning speed and wire feeding speed condition.The number of pores in the cladding layer obtained by this method is effectively limited.And,in unit time and unit power conditions,the deposition efficiency increases with the increases of wire feed speed,and decreases with the increase of laser power.It is found that the maximum deposition efficiency is about 0.87 kg/(h·kW),which is three times higher than traditional laser additive manufacturing technology.On the basis of forming good single cladding layer,we get the best overlap rate is 43.3%,overlapping area and non-overlapping zone growth along the direction of the inverse heat conduction tissue,microhardness of overlap region and non-overlapping area show small difference,the change of microhardness in different regions is subtle.The microstructure of different depositional layers in different accumulation ways are mainly equiaxed and dendrite.Due to the existence of heat-affected zone,the grain sizes of different regions are different.The microhardness of the two stacking methods is almost uniform.