The X-ray diffraction method was applied to the measurement of residual stresses on the ground or polished surfaces of WC-Co alloys with various Co contents. The X-ray diffractions of WC 211 by Cu K α radiation were used for the stress measurement. The residual stresses on the ground or polished surfaces were all compression. For the same Co content, the compressive value increased with increasing surface roughness. The maximum residua) stress, which was -2.13 GPa, was observed in WC-5.5wt%Co ground with a #140 diamond wheel.
The bending strengths of each alloys were obtained by three point bending tests. The bending strengths were influenced by grinding conditions and Co contents. The maximum value of 3.6 GPa was obtained in WC-16.0wt%Co ground with a #140 diamond wheel.
For the same Co addition, the bending strengths were closely related to the residual stresses, These relations were approximated by straight lines.