Fabricating Silicon Carbide Parts By Selective Laser Sintering/Cold Isostatic Pressing And Post Process

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 re search contents and results 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 and epoxy resin E12, stearic acid and nylon 12 were selected as binder. The composite powders were prepared by different ways and the methods were compared.The effect of process parameters on SLS was studied. The least binder E12 content of E12-SiC powder was 6 wt.% and strength of the green body was enough when E12 content was 10 wt.%. The SLS process parameters on E12-SA-SiC powder were optimized, relative density of the green body reached 35.13% when the laser energy density was 0.034 J/mm2; relative density of the green body was higher when the laser power, scanning speed, scanning space were 5 W, 2200 mm/s, 0.08 mm. To improve the content of stearic acid or decrease laser power was beneficial to improve the dimensional precision. The infiltration- debinding process was better, density of the green body increased from 0.98 g/cm3 to 1.11 g/cm3 after the process.The effect of process conditions on bending strength of SLS and SLS/CIP specimens was studied. Relative density of the SLS/CIP specimen reached 63.79% after CIP treatment under 200 MPa. Debinding and pre-sintering process was formulated by TG curve of the binder. Relative density and bending strength of the specimen reached 92.98%, 56.2MPa after pressureless sintering at 2000℃.Therefore, based on the study of SLS/CIP 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.