Research On Surface Quality And Density Of GH4169 Parts Fabricated By Selective Laser Melting

Selective laser melting(SLM)is an advanced technology in addictive manufacturing field and it has broad application prospects in automotive,aerospace and other fields.SLM can fabricate terminal or near-terminal metal parts directly,however,the surface quality and density of the forming parts can hardly reach to the optimum state.In this paper,GH4169 alloy was selected as the experimental material.The research aimed to improve the surface quality and density of the SLM forming parts and systematically studied the effects of process parameters on them.By designing the orthogonal experimental program,the effects of process parameters on surface quality and density of the forming parts were researched firstly.Then the process parameters were combined together and the effect of energy input on the results was studied.Finally,this research analyzed the interactive effect of the upper surface quality and density of forming parts.At the same time,not only the surface defects,such as incompletely melted powders,over-melted phenomenon,the spheroidization,and powders adhesion phenomenon,but also the internal defects such as hole,incomplete fusion,and crack were studied.The results of study on upper surface quality and density of the forming parts showed that the laser power,the scanning speed and the scanning interval had great influence on the surface quality and density of the forming parts,while the scanning strategy had little influence on the surface quality and density of the forming parts.The optimal combination of process parameters was that the laser power was at 320 w~340 w,the scanning speed was at 1000 mm/s ~1200 mm/s,the scanning interval was 60 μm,and the scanning rotation angle was 67 degrees.The surface roughness was small and the density was high at this time.After considering different factors,it could be drawn that the surface quality was good and the density was high when the volume energy density was at 130 J/mm3 ~150 J/mm3,and the overlap rate was at 30~40%The results of study on the side surface quality showed that the side surface was mainly affected by laser power,and the side surface quality was good especially when the laser power was 300 w.The side surface quality was worse with decrease of the side surface tilt angle.When the tilt angle was 30 degrees,the side surface was not able to fuse.Under the same process parameters,the upper surface quality of the forming parts was generally better than the side surface quality,and the Ra value of the side surface was 2.97 μm higher than the Ra value of the upper surface.After comparing and analyzing the surface quality and density,and studying from the volume energy density and the overlapping ratio perspectives,the interactive effect of the upper surface quality and density was found that Ra value and density were negatively correlated.