Research On The Influence Of Die Steel Matrix Factors On The Quality Of Laser Melt Deposition

At present,with the continuous improvement of industrial production level,as the most basic industrial production equipment,molds have their own high performance requirements or harsh working environment,making the surface modification and failure repair of molds have increasingly higher practical application value.Laser melting deposition technology is a new type of additive manufacturing technology that has been rapidly developed in recent years and can be used for mold surface modification and failure repair.It has also done a lot in terms of factors affecting its deposition quality(laser power,scanning speed,etc.)However,little attention has been paid to the influence of the factors of the substrate to be deposited on the quality of the deposited layer.The surface morphology of the substrate will affect the absorption of laser energy on the surface of the substrate;the matrix composition will affect the diffusion of chemical elements during the solidification of the deposited layer;the relative orientation of the substrate and the laser beam will affect the flow of liquid metal in the molten pool;these substrates themselves The factors will eventually affect the macroscopic morphology,microstructure and mechanical properties of the sedimentary layer.The research of the project is to design single-layer single-layer,thin-walled,multi-layer overlap,multi-layer multi-layer deposition experiments according to the different degrees of influence of various matrix factors on the relevant characteristics of the sedimentary layer(macro morphology,microstructure,mechanical properties)Analyze the experimental results and summarize the law of the substrate's own factors on the quality of the laser deposition,and finally provide theoretical and experimental basis for the modification and repair of the mold,and provide new ideas for the control of the deposition quality.In this paper,316L is used as the material of the deposition layer,and the influence of the matrix of the mold steel on the quality of laser melting deposition is studied.The main research contents are as follows:(1)With the increase of the substrate surface roughness,the 316L deposition layer has a significant effect.The results show that the macroscopic morphological dimensions of the deposition layer(melt width,melt height,and melt depth)will increase,and in the Argon environment,the increase in melt height and melt depth will reach 100%,while the increase of melting width is relatively gentle;the dilution rate of sedimentary layer tends to 55%.Stacked 10 layers,the height of the sandblasted substrate reached 2.5mm,and the height of the milling surface was only 1.25mm.As the number of stacked layers increased,the height effect gradually weakened;and the internal porosity of the sandblasted substrate deposition layer was only 31%of the milling,This is because the increase in roughness improves the bonding surface between the deposited layer and the substrate,so that subsequent deposited layers have a very good bonding surface,thereby reducing the porosity.For multiple overlapping depositions,the effect of roughness is mainly concentrated on the longitudinal dimension of the cross section of the deposited layer.The increase in roughness causes the internal columnar crystals to become coarse and uneven.As the roughness increases,the tensile strength inside the deposited layer increases,which improves the mechanical properties inside the deposited layer to a certain extent.(2)The difference of matrix composition has a great influence on the appearance quality of the 316L sedimentary layer and the morphology of the bonding zone,and different degrees of defects are generated inside the sedimentary layer;the growth state of the internal layer of the sedimentary layer is very different;the composition of the substrate affects the elements of the sedimentary layer.Diffusion causes the distribution of major elements such as Fe,Cr,Mn,and Ni to be significantly different.Due to the different content of internal elements in the sediment layer,different compounds are formed inside,which ultimately leads to a hardness difference of 65%.The diffusion of elements near the bonding zone is affected,and the hardness of the heat-affected zone and the bonding zone are also greatly different.(3)The relative spatial position of the substrate and the laser beam will affect the deposition quality.The laser beam is deposited vertically downward:When the substrate inclination angle is less than 30 degrees,the appearance quality of the deposited layer increases with the inclination angle,and the melting width continues to increase.The penetration depth gradually decreases,the dilution rate increases,and exceeds 60%;when the inclination angle is too large,gravity and powder beam force work together to reduce the appearance quality.The laser beam is perpendicular to the substrate surface:when the angle is small,the macroscopic morphology of the deposited layer is good and the cross-section quality is controllable;in this state,the molten pool is only affected by gravity and the energy distribution of the light spot is uniform,resulting in better quality of the deposited layer.Two laser beam posture states:For small-angle deposition,the laser beam can be deposited straight down,which is a simple process.For higher quality of the deposited layer,high-precision deposition repair,the position of the laser beam perpendicular to the substrate surface should be used.