Corrosion behaviour of silicon carbide–diamond composite materials in aqueous solutions

The corrosion behaviour of the relatively new silicon carbide bonded diamond materials (ScD) was investigated in NaOH, H2SO4 and hydrothermal conditions and compared with that of conventional SSiC and SiSiC-materials. The corrosion resistance increases with decreasing diamond grain size. In H2SO4 all investigated materials show a very high corrosion resistance, whereas in NaOH and under hydrothermal conditions above 100 °C some leaching of residual silicon takes place. Nevertheless the fine grained ScD material exhibits a residual strength of 400 MPa after 200 h corrosion in NaOH at 90 °C. Under the same conditions the strength of the SiSiC-material reduces to 50 MPa. The silicon carbide-diamond composites demonstrate corrosion resistance superior to SiSiC and wear properties analogous to that of conventional superhard materials. This material would therefore be suitable for use in demanding corrosive wear applications.