SXRD measurements of residual stresses in sintered diamond–cobalt composites

Diamond-cobalt composites are used for cutting tools. Residual stress after manufacturecan reduce the lifetime of such composite cutting tools and, hence, the stress state needs to be wellunderstood. Within this study, stress measurements on a cobalt diamond composite were made bySXRD to deduce stress states in the cobalt matrix using the (222) reflection. The application ofdifferent apertures allowed the investigation of stress in small areas of cobalt surrounding adiamond and in areas at different distances to a diamond. In the areas adjacent to the diamondincreased residual stresses were found in the cobalt matrix. Furthermore, approximations for radialand tangential residual stresses have been derived which show to be different

Residual stresses in sintered diamond–cobalt composites

Manufacturing diamond-cobalt composites by sintering results in residual stresses due tothe mismatch of thermal expansion coefficients mainly. To understand the influence ofmanufacturing process parameters on residual stresses of sintered diamond-cobalt compositessamples are produced by different process parameters. The investigated diamond composites arepressureless sintered as well as pressureless sintered combined with hot isostatically pressing. Herethe influence of powder characteristics and process parameters like compaction pressure andsintering temperature on the residual stresses and microstructure was analysed by X-ray diffraction,microscopy and tomography. The aim of this study is to correlate residual stresses withmanufacturing parameters and to give hints for optimising the residual stress state and forimproving the lifetime of diamond-cobalt composites