Experimental Study On Preparation And Machining Of Ni60 Laser Cladding Layer

ASM(Additive and Subtractive Manufacturing)is a new green manufacturing method,which fully embodies the advantages of additive manufacturing based on laser cladding and traditional machining technology.AM(Additive Manufacturing)based on laser cladding breaks through the shackles of traditional SM(Subtractive Manufacturing),and the manufacturing concept of “grow out of nothing” realizes the rapid manufacturing of complex structure.However,the manufacturing method of “layer by layer” can not guarantee the dimensional accuracy and surface quality,so it is necessary to ensure the production quality through subsequent machining.The automobile panel die is prone to crack and wear under the action of high pressure and impact.The residual value of the mold can be brought into full play by ASM based on laser cladding to repair the damaged area,which is of great significance to reduce the production cost and improve the utilization rate of resources.To improve the quality of laser cladding and subsequent cutting is the necessary guarantee for the repair quality of the die.Therefore,a fiber laser is used to prepare Ni60 cladding layer on Cr12 MoV die steel.The machining rules of cladding materials are analyzed through milling experiment,and the influence of cutting parameters is elaborated in detail,which provides guidance for efficient machining laser cladding materials.The main research contents and conclusions are as follows,(1)Ni60 Alloy powder cladding layer was prepared on Cr12 MoV die steel by 4000 W fiber laser.The influence of laser cladding parameters on the forming quality of the cladding layer was studied by the geometry size of the cross-section sample.Then,the microstructure and hardness distribution of the cladding layer were analyzed by metallographic microscope and microhardness tester.Moreover,the inhomogeneous characteristics of the microstructure and hardness distribution of the laser cladding material were analyzed.On this basis,high quality laser cladding layer with compact structure and no crack defect was prepared by optimized laser cladding parameters.(2)Single bead Ni60 cladding samples were prepared under the condition of optimized cladding parameters,and the milling experiments of cladding layer were carried out on CNC machining center.The chip samples of cladding layer were observed by metallographic microscope and digital microscopy.Then,the effects of milling parameters on chip morphology and chip deformation were analyzed.(3)The cutting forces were recorded by using Kistler-9257 b dynamometer,and the maximum cutting force in steady state was token as the research object.Then,the influence of cutting parameters on cutting force was analyzed,and the empirical formulas of cutting force were fitted by MATLAB.(4)The milling temperature was measured by Infrared Thermal Imager,and the machined surface quality was detected by Surface Roughness Meter.Then,the influence of cutting parameters on milling temperature and surface roughness was analyzed based on orthogonal experiment.The empirical formulas of cutting temperature and surface roughness were obtained.The results show that:(1)The height,width and dilution ratio of the cladding layer are greatly affected by the laser power,scanning speed and powder feeding rate.The microstructure of the cladding layer basically grows along the direction of thermal diffusion,and has the characteristics of directional rapid solidification.From the bottom to the surface of the cladding layer,lamellar planar crystals,cellular/columnar dendrites and equiaxed crystals appear successively.(2)The chip morphology of Ni60 cladding layer is continuous chip.The spindle speed,feed rate per tooth and radial cutting depth has great influence on the chip morphology,but the axial cutting depth has no significant influence.The deformation coefficient decreases with the increase of spindle speed,feed rate per tooth and radial cutting depth,and is less affected by axial cutting depth.(3)The cutting force increases with the increase of spindle speed,feed rate per tooth,axial cutting depth and radial cutting depth.The axial cutting depth has the greatest influence on the cutting force,followed by the feed rate per tooth,the radial cutting depth and the spindle speed.And,the accuracy of empirical formulas of cutting force meets the requirements of engineering application.(4)The cutting temperature increases with the increase of spindle speed,feed rate per tooth,axial cutting depth and radial cutting depth.The surface roughness decreases with the increase of spindle speed,while increases with the increase of feed per tooth and axial cutting depth.And,it has little relationship with radial cutting depth.The empirical formulas of cutting temperature and surface roughness can meet the needs of engineering application.