Research Of Silicon Carbide Components Via Selective Laser Sintering Combined With Reaction Sintering

The silicon carbide parts have many good properties,such as high strength,high hardness,low density,good chemical stability and excellent high temperature performance.So they are widely applied in aerospace,petrochemical,nuclear energy fields.But it is difficult to form and process because of the high melting point and brittle characteristics.Especially for complex parts,the traditional methods are difficult or even impossible to form.The purpose of this paper is to study the selective laser sintering/cold isostatic pressing compound process and post treatment of silicon carbide.The main research contents are as follows:SLS forming mechanism was described.Polymer material was chosen as the SLS binder,the CO₂ laser absorption rate of it can reach 96%,far higher than the YAG laser and CO₂ laser is more suitable for SLS process.Different polymer materials were compared an phenolic resin 2123 was selected as binder.Compared with the advantages and disadvantages of preparation methods,The phenolic resin-SiC composite powders was prepared by mechanical mixing method.The effect of process parameters on SLS was studied.The least binder phenolic resin content of phenolic resin-SiC powder was 16 wt.%and strength of the green body was enough when phenolic resin content was 30 wt.%.The SLS process parameters on phenolic resin-hexamethylenetetramine-SiC powder were optimized,relative density of the green body reached 31.9%when the laser energy density was 0.04 J/mm²;relative density of the green body was higher when the laser power,scanning speed,scanning space,layer thickess were 8 W,2000 mm/s,0.1 mm,0.15 mm.In order to explore the methods to improve the quality of forming parts,we can improve the preheating temperature,control of cooling speed,decreass content of bonding agent and the laser energy density,all of which are helpful to reduce the tendency to warp.The carbonization temperature process was formulated by TG curve of the binder.,which can effectively guarantee the carbonization process stability,maintain the shape of the sample is complete,and avoid cracking sample.After 1500℃high temperature siliconizing,respectively on the silicon carbide sample after siliconizing phase analysis,fracture morphology analysis,performance analysis and the analysis of the shrinkage rate.Relative density and bending strength of the specimen reached 86.66%,81MPa.Therefore,based on the study of SLS/RBCS compound process of silicon carbide parts and post process,complex ceramic parts can be manufactured by this method,which provides a new method for manufacturing complex shape silicon carbide parts,is also very meaningful for widening engineering application of SLS technology.