Influence of resin content and compaction pressure on the mechanical properties of SiC–Si composites with sub-micron SiC microstructures

The influence of resin content (15–20, 25 wt.%) and compaction pressure (75, 100, 125 MPa) on the mechanical properties and microstructure of SiC–Si composites with sub-micron microstructure has been evaluated. To produce the composites three powders with particle sizes in the range of 0.22–0.70 μm were used. Before application the SiC powders were treated with hydrofluoric acid to remove the extent of SiO2. Due to this treatment a successful infiltration of green-bodies, even of those produced of SiC powder with a mean particle size of 0.22 μm, was possible. The fracture toughness and bending strength increased with increasing resin content. The highest value of strength was observed at 733 MPa for the composites produced of SiC powder with a mean grain size of 0.70 μm and a resin content of 25 wt.%. Within this composite the free silicon content was reduced to 12 vol.%. In regard to previous experiments this is a reduction of more than 50%. These results are a consequence of the lowering of the free silicon content of the composites when increasing the resin amount. With decreasing SiC starting particle size the mechanical properties decreased but they were independent on compaction pressure.