Study On The Influence Of Process Parameters And Ultrasonic Treatment On The Surface Quality Of Selective Laser Melting Die Steel

Selective laser melting has attracted extensive attention in the field of mold manufacturing due to its advantages of high forming accuracy and no limitation of shape However,since part of the powder will adhere to the surface during the manufacturing process,the surface roughness of the directly printed part is high.In addition,for a complex mold with a heat dissipation inner cavity flow path,the surface sticky powder will affect the flow of the cooling liquid,and will also bring about the cooling liquid pollution caused by the falling off of the sticky powder.In this paper,18Ni300 thin samples with different parameters are printed by using selective laser melting,and the effects of different printing parameters on the surface stickiness and surface roughness of the parts are explored.Block samples were printed with fixed parameters,and the feasibility of ultrasonic cleaning on the post-treatment of selected laser melted 18Ni300 surfaces was studied,as well as the effects of different ultrasonic cleaning media and ultrasonic working parameters on surface treatment effects.Through comparative analysis,the rule of 18Ni300 mold steel printing parameters and ultrasonic post-treatment conditions on the surface quality of the formed parts was obtained.Image-Pro mathematical statistics,SEM,surface roughness measurement,etc.are used to characterize the surface conditions obtained different parameters,and the results are analyzed to find out the rules.The results show that when the laser power is constant,the surface sticky powder has a minimum value with the increase of scanning speed,and the scanning speed that produces the minimum surface sticky powder increases with the increase of laser power.There is a threshold for the effect of scanning speed on surface roughness.Before reaching the threshold,the surface roughness will change greatly with the increase of scanning speed.After the threshold is exceeded,the surface roughness will not change significantly as the scanning speed increases.The effect of laser power on surface sticky powder and surface roughness is similar.At lower scanning speeds,laser power has a greater impact on surface sticky powder and surface roughness.Surface roughness is insensitive to changes in laser power.Ultrasonic cleaning method has a more obvious effect on the surface treatment of selected laser melting parts.After treatment,the surface roughness Ra,Rz and the amount of powder are reduced.Aqueous solutions and diamond suspensions are not effective in removing embedded powders.The nitric acid alcohol solution can obtain a non-stick powder treated surface,but due to the fall of the embedded powder,a pit is left in the portion where the powder was originally adhered,which affects further reducing the surface roughness of the part.Ultrasonic cleaning is more effective at 500 W within the same processing time and operating frequency.Compared with 40 Khz,the surface roughness and the amount of sticky powder obtained at 60 KHz are lower.