Characterization of the residual stresses introduced by a new joining method in diamond and tungsten carbide composites

In this work, a co-sintering method was used to attach diamond to cemented carbide composites. The joining method consists of sintering a green part (ring) of cemented carbide (CC) around a thermally stable diamond composite (TSDC) part (plug) to radially contain it. During the sintering step, the green body shrinks to a controlled level and therefore forms interference fit between the two parts (mismatch between the inner diameter (ID) of the CC ring and the outer diameter (OD) of the TSDC cylinder). The residual stresses induced by this process as well as the bond strength between the CC and the TSDC parts were quantitatively evaluated. It is shown that the interface pressure between the two parts, and the level of residual stresses, increased with increase in the designed interference fit, as well as with the increase of the ID/OD ratios of the CC ring. For the chosen material combination (cemented carbide ring comprised 90 vol% WC and 10 vol% Co with medium coarse WC grains; diamond composite plug comprised 84 vol% diamond and 16 vol% SiC), the values of the hoop stresses at the interface in the CC ring measured by neutron diffraction was determined to be between 150 MPa and 550 MPa, depending on the ID/OD ratio. It was also found that for a given ID/OD ratio, the increase of the designed interference fit had little effect on that attained due to the plastic deformation of the cemented carbide material at the interface during the sintering (dynamic) process. A mechanical bond around 60 MPa was nevertheless achieved.