Influence of the brazing parameters on microstructure, residual stresses and shear strength of diamond–metal joints

The reliability and integrity of diamond cutting tools depend on the properties of diamond-metal joints as created by a brazing process. Block-shaped monocrystalline diamonds were brazed onto a steel substrate (X2CrNiMo 18-14-3), using silver-copper based Cusil-ABA™ (Ag-35wt%Cu-1.75wt%Ti) filler alloy. The experimental procedure includes a thorough microstructural investigation of the filler alloy, the determination of the induced residual stresses by Raman spectroscopy as well as the joint's shear strength utilizing a special shear device. The brazing processes were carried out at 850, 880 and 910 °C for dwell durations of 10 and 30 min, respectively. At the steel interface two interlayers develop. The layers grow with extended dwell duration and higher brazing temperature. The residual stresses only slightly depend on the brazing parameters and exhibit a maximum value of -400 MPa. Unlike the residual stresses, the shear strength strongly depends on the brazing parameters and thus on the microstructure. Three failure modes could be identified; a ductile fracture in the filler alloy, a brittle fracture in the interlayers and a partly shattering of the diamond. © 2010 Springer Science+Business Media, LLC.