Study on the Carbon Pollution in SPS

In order to study the pollution of graphite die on the sintered material in spark plasma sintering (SPS), The metal tungsten as the material and the graphite die were heated in SPS by a pulse direct current. The pollution of carbon was studied when the tungsten was sintered by SPS at 1 500℃ or 1 900℃ with applying pressure of 30 MPa. By means of X-ray analysis and SEM observation and thermodynamic calculation, it was found that graphite could directly react with tungsten. Carbide pollution layer was formed at about 300nm deep from the surface. There was only tungsten under 500nm from the surface. The pollution layer was composed of WC at 1 500℃, and of WC and W₂C at 1 900 ℃.