Study On Coating Strengthening And Cutting Performance Of Laser Micro-textured Tool

With the rapid development of technology-intensive industries such as resource exploitation,ocean exploration,aerospace and so on,various kinds of hard-to-cut materials such as super heatresistant,wear-resistant,corrosion-resistant alloys and carbon fibers have sprung up.As a highend cutting tool,coated tool has a utilization rate of more than 50% in the industry.However,due to the bad cutting conditions,the difference of thermal expansion coefficient between coating and substrate and the residual stress in coating lead to poor coating/substrate bonding,and the coating is prone to cracking and peeling during cutting,which seriously reduces the service life and processing quality of coated tools.Aiming at this technical problem,the laser micro-texture technology is used to insert texture on the surface of the tool base and then prepare the surface coating to enhance the bonding strength of the coating/substrate and enhance the wear resistance of the coated tool.Meanwhile,the effect of friction reduction and debonding of tool surface texture is brought into play,and the cutting performance of coated tool is improved synergistically.The main contents of this paper are as follows.(1)According to the process of tool coating preparation and the bonding mechanism,it is expounded that the micro-texture can be the basis for introducing mechanical anchorage into the coating and substrate;the main failure reason of the tool coating is analyzed,which is due to the excessive residual stress in the coating,resulting in cracks and warpage at the coating/substrate bonding interface,and the interface bonding morphology and laser addition are explained.Based on the theory of metal cutting,the effect of texture on the contact length between tool and chip is analyzed,and the scheme of texturing substrate surface is put forward according to the wear form of cemented carbide coated tools under common working conditions.(2)The three-dimensional models of different textured tool were established by UG NX software.After adding coatings,meshing and setting parameters in DEFORM-3D software,the cutting simulation was carried out,and the cutting force,cutting temperature,wear morphology of three coated tools were compared.The results show that the cutting force and cutting temperature of coated texture cutter can be reduced by 24.15% and 9.36% compared with common coated cutter.Grooves and texture on the surface of substrate can effectively reduce the wear of the rake face of coated cutter,and the distribution of maximum wear depth is related to texture morphology.(3)In order to explore the relationship between processing parameters and texture morphology,the laser micro-texture process experiment was carried out.The influence of different processing parameters on texturing and groove morphology geometry parameters was investigated by single factor variables.The forming mechanism of concave-convex composite morphology and the effect of laser pulse on material flow were expounded through physicochemical analysis of texturing area.Aiming at the lack of laser processing method which can actively control the profile of groove section,a new method of groove texture laser processing,parallel forming method,was proposed based on the principle of "copying processing".By setting the initial spacing of grooves and adjusting the distribution law of grooves,the overlap rate of ablation area can be changed,and different machining allowances can be achieved finally.The groove depth makes the interior contour of the groove transit smoothly as possible,which is convenient for coating deposition.Through texture quality evaluation and morphological size inspection,texture morphological size and corresponding laser processing parameters were optimized.(4)Textured cemented carbide samples with different area occupancies of texture and groove were prepared.TiAlN coatings were deposited by PVD technology.The micro-morphology of TiAlN coatings before and after texture coating were compared,and the "re-mapping" effect of the coatings on texture morphology was verified.According to the scratch failure characteristics of the coatings,the bonding mechanism between the coatings and the textured matrix and the texture configuration of the matrix surface were analyzed.Meanwhile,the groove has the function of restraining the failure extension of the coating to a certain extent.According to the test results,the microhardness,residual stress and bonding strength of coatings with different textures were characterized.The results show that the wool morphology with a certain area occupancy is beneficial to improve the microhardness of the coatings.The groove morphology has a small effect on the microhardness of the coatings,and the area occupancy has little effect on it.Both texture morphologies can reduce the residual stress in the coatings.The decreasing range of residual stress is positively correlated with the area occupancy of texture.The texture with a certain area occupancy is beneficial to enhance the microhardness of the coatings The bonding strength of coatings is better than that of grooves.The bonding strength of coatings can be increased by 19.2% at the highest level.If the texture density is too high,the bonding strength of coatings will be reduced.(5)According to the above research results,three kinds of tool samples,TiAlN non-texture coated tool,groove texture coated tool and texture coated tool,were prepared by using laser microtexture technology and PVD technology.The effect of matrix surface texture on cutting force,cutting temperature and wear morphology of coated tool was studied by Inconel 718 high-speed turning test.The results show that the cutting performance of coated tool can be improved and the wear area of rake face can be reduced by placing texture on the substrate surface.Through the analysis of the mechanism of micro-texture,the difference between groove and texturing on the performance of coated tools is revealed.The groove reduces the contact area between tool and chip,and is more conducive to reducing cutting force and cutting temperature.The mechanical anchoring effect produced by texturing morphology and the effect of controlling residual stress of coated tools are more conducive to enhancing the wear resistance of coated tools.