Spark plasma sintering of tungsten/graphite joints with a SiC ceramic interlayer

Tungsten powders were successfully sintered and simultaneously joined to a graphite disk using an interlayer of SiC ceramic powder, which contained Al2O3 and Y2O3 as sintering aids for the SiC. The tungsten/graphite joints were prepared at 30 MPa and temperatures ranging from 1700 °C to 2000 °C for 5 min using spark plasma sintering (SPS). The tensile strength of the joints prepared at 1700 °C reached 21 MPa. The suggested joining mechanism of the joints prepared below 1800 °C is as follows: both the sintered W metal layer and the SiC ceramic interlayer are chemically bonded together accompanying reaction phases of WC, W2C and W5Si3. A physical bond is achieved between the SiC interlayer and graphite when the SiC powder fills the open pores of the graphite and is sintered there. Although a similar joining mechanism is suggested when the joining temperature exceeds 1900 °C, the SiC interlayer disappears, and the broad reaction layer consisting of WC, W2C and trace W5Si3 is formed.