| Selected Laser Sintering(SLS)is a kind of additive manufacturing technology based on discrete-stacking principle to realize rapid prototyping.Because its process itself breaks through the production mode of subtractive manufacturing in traditional machining in principle,it can process forming parts with complex geometric shapes.Therefore,it has a wide application prospect in the fields of construction,medical treatment,education,electronics,aerospace and so on.At present,the raw materials used in laser sintering technology have the disadvantages of high cost and weak functionality.In this paper,low-cost Polyethersulfone resin(PES)was used as a polymer matrix material,and graphite(GP)and carbon fiber(CF)were added to develop CF/GP/PES conductive polymer composites suitable for selective laser sintering technology.The effects of filler shape,content,laser sintering process parameters and heat treatment process on the microstructure and properties of CF/GP/PES laser sintered parts were studied.CF/GP/PES composite powder was prepared by mechanical mixing method,and CF/GP/PES sintered parts were prepared by SLS technology.Firstly,the effects of the shape and content of fiber CF and flake GP blending fillers on the powder spreading condition,microstructure and properties of CF/GP/PES composite powder were studied.Considering the influence of the change of the mass fraction of the matrix powder on the properties of the sintered parts,the total content of CF/GP blending fillers was fixed,the ratio of blending fillers was changed,and the influence of the shape of CF/GP blending fillers on the microstructure and properties of sintered parts was analyzed.It is found that the flake GP is easier to form a conductive network in the matrix,and the fibrous CF can maintain and promote the mechanical properties of the sintered parts.Therefore,the mass fraction of GP is fixed at 20%,and the effect of CF mass fraction of 1%-11% on the microstructure,mechanical properties and electrical conductivity of the sintered parts is further studied.The influence of laser sintering process parameters on CF/GP/PES sintered parts was studied.Firstly,the laser sintering mechanism of CF/GP/PES composite powder was analyzed by combining the tensile fracture microstructure pictures of CF/GP/PES composite powder and sintered parts.The effects of preheating temperature from 70℃ to 82℃on the formability,microstructure and properties of CF/GP/PES composite powders were studied,and the optimum preheating temperature for laser sintering of CF/GP/PES composite powders was obtained.Because the laser power has a great influence on the properties of sintered parts,the effects of laser power from 10 W to 30 W on the forming properties,microstructure,mechanical properties and electrical conductivity of CF/GP/PES composite powders were studied according to the selected optimal preheating temperature of 80℃.Finally,the laser power suitable for CF/GP/PES composite powders was obtained.As an effective way to improve material properties,heat treatment is also often used in polymer materials to improve material properties.In order to further improve the mechanical properties and electrical conductivity of CF/GP/PES sintered parts,the heat treatment process of CF/GP/PES laser sintered parts was studied in this paper.Firstly,the dimensional accuracy and properties of the sintered parts before and after heat treatment were compared.It was found that the mechanical properties and electrical conductivity of the sintered parts after heat treatment were greatly improved.Therefore,the heating method,heating temperature,holding time and cooling method of heat treatment of CF/GP/PES sintered parts were further studied.The effects of heat treatment process on the microstructure,mechanical properties,electrical conductivity and surface roughness of sintered parts were studied,and the best heat treatment process suitable for CF/GP/PES sintered parts was explored. |
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