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 degrees C to 2000 degrees C for 5 min using spark plasma sintering (SPS). The tensile strength of the joints prepared at 1700 degrees C reached 21 MPa. The suggested joining mechanism of the joints prepared below 1800 degrees 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 degrees C, the SiC interlayer disappears, and the broad reaction layer consisting of WC, W2C and trace W5Si3 is formed. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.